Double C-H Functionalization to Construct Polycyclic Heteroarenes Catalyzed by an Ionic Salt of a Pd Complex with an N-Heterocyclic Carbene Ligand

Article abstract of DOI:10.1002/ejoc.201500417

A new ionic salt, cis-[Pd(L)(PPh₃)(H₂O)₂](SO₃CF₃)₂ (A), in which L is an amido-functionalized N-heterocyclic carbene (NHC) ligand, has been prepared by the salt metathesis reaction between [Pd(L)(PPh₃)Cl₂] and AgOTf in wet acetonitrile. It was successfully characterized by NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction analysis. Complex A was found to be effective in catalyzing the double C-H functionalization of various nitrogen- and sulfur-containing heteroarenes to form fused polycyclic heteroaromatic compounds with alkynes in the presence of Cu(OAc)₂ and tetra-n-butylammonium bromide. Indoles, thiophenes, imidazo[1,2-a]pyridine, and imidazoles were used as substrates. In particular, intriguing imidazo[5,1,2-cd]indolizine compounds could be obtained under the conditions employed. The complex cis-[Pd(L)(PPh₃)(H₂O)₂](SO₃CF₃)₂, in which L is an amido-functionalized N-heterocyclic carbene (NHC) ligand, has been prepared. This complex was effective in catalyzing the double C-H functionalization of various nitrogen- and sulfur-containing heteroarenes to form fused polycyclic heteroaromatic compounds with alkynes in the presence of Cu(OAc)₂ and tetra-n-butylammonium bromide.

Full text of DOI:10.1002/ejoc.201500417

FULL PAPER
DOI: 10.1002/ejoc.201500417
Double C–H Functionalization to Construct Polycyclic Heteroarenes Catalyzed
by an Ionic Salt of a Pd Complex with an N-Heterocyclic Carbene Ligand
Sanjay Kumar Ghosh,[a] Bing-Chiuan Kuo,[a] Hsiang-Yu Chen,[a] Jia-Ying Li,[a]
Shuang-De Liu,[a] and Hon Man Lee*[a]
Keywords: Homogeneous catalysis / C–H activation / Palladium / Carbene ligands / Nitrogen heterocycles
A new ionic salt, cis-[Pd(L)(PPh3)(H2O)2](SO3CF3)2 (A), in
which L is an amido-functionalized N-heterocyclic carbene
C–H functionalization of various nitrogen- and sulfur-con-
taining heteroarenes to form fused polycyclic heteroaromatic
(NHC) ligand, has been prepared by the salt metathesis reac- compounds with alkynes in the presence of Cu(OAc)2 and
tion between [Pd(L)(PPh3)Cl2] and AgOTf in wet acetonitrile. tetra-n-butylammonium bromide. Indoles, thiophenes, imid-
It was successfully characterized by NMR spectroscopy, ele- azo[1,2-a]pyridine, and imidazoles were used as substrates.
mental analysis, and single-crystal X-ray diffraction analysis.
In particular, intriguing imidazo[5,1,2-cd]indolizine com-
Complex A was found to be effective in catalyzing the double
pounds could be obtained under the conditions employed.
tive in mediating the double C–H functionalization of vari-
ous nitrogen- and sulfur-containing heteroarenes to form
fused polycyclic heteroaromatic compounds with alkynes.
Introduction
Transition-metal-catalyzed C–H bond functionalization
has become an increasingly important tool for the construc-
tion of fused polycyclic heteroaromatic compounds.[1–3]
This process provides a simple, direct, and atom-economic
access to π-conjugated heteroaromatic molecules, which at-
tract considerable attention not only because of their bio-
logical and pharmacological activities,[4] but also for their
applicability to organic electronics and luminescent materi-
als.[5] In general, aromatic substrates containing hydroxy-,
carboxy-, amido-, and phosphine oxide functions are em-
ployed in the catalytic process, and these heteroatom-con-
taining groups, after coordination to the transition metal,
act as directing groups for regioselective C–H bond cleavage
at the ortho position.[2] A significant recent advance in C–
H bond functionalization for the generation of polycyclic
aromatic compounds was the use of π-electron units, in-
cluding alkenyl, alkynyl, aryl, heteroaryl, and cyano groups,
to trigger ortho-C–H bond functionalization. In this regard,
the dehydrogenative annulation of nitrogen- and sulfur-con-
taining aromatic compounds with internal alkynes through
C–H bond cleavage has been recently reported.[3] However,
for the newly reported Pd-catalyzed oxidative annulation, a
high catalyst loading was required and essentially no other
nitrogen-containing compounds other than indoles have
been used as substrates.[3a] Herein we wish to report a new
ionic salt of a palladium NHC complex that is highly effec-
Results and Discussion
Preparation of the Ionic Salt of Palladium N-Heterocyclic
Carbene (A)
Our target palladium complex A for use in double C–H
functionalization is shown in Figure 1. The NHC ligand (L)
features an amido functional group and such a ligand scaf-
fold has been proven to be efficient in a variety of cross-
coupling reactions.[6] We envisioned that the NHC=O func-
tionality would be involved in the molecular recognition of
the acetate anion; a vicinal acetate anion around the metal
center should be crucial for the C–H activation of heteroar-
enes in the catalytic process (see below). The new ionic salt,
[PdL(PPh3)(H2O)2](OTf)2 (A), could be easily synthesized
from the salt metathesis reaction between the known com-
plex [Pd(L)(PPh3)Cl2][6b] and AgOTf in wet solvent. We en-
visioned that the absence of coordinating chloride anions
would enhance the availability of coordination sites for the
1
incoming substrates. The H NMR spectrum of A exhibits
a singlet due to the NH proton at δ = 10.40 ppm and the
absence of NCHN signal at around 9.5 ppm,[6b] which indi-
cates that the NHC ligand is coordinated to the PdII ion in
a monodentate fashion. The 31P NMR spectrum shows a
signal at δ = 27.8 ppm. Complex A should adopt a cis ge-
ometry, by comparison with other compounds reported in
the literature.[6b,6c] The cis disposition of the ligands was
confirmed by the ROESY spectrum of the complex, which
exhibits through-space correlations between the phenyl pro-
[a] Department of Chemistry, National Changhua University of
Education,
Changhua 50058, Taiwan, R.O.C.
E-mail: leehm@cc.ncue.edu.tw
http://chem.ncue.edu.tw/people/bio.php?PID=10
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201500417.
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H. M. Lee et al.
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tons of the PPh3 ligand and the CH2 and NH protons of resulted in a 45% yield of the product (entry 6). However,
the NHC ligand (see Figure S5 in the Supporting Infor- this activity of the neutral complex [Pd(L)(PCy3)Cl2] bear-
mation). The structure of A was further established by sin- ing a more electron-donating PCy3 ligand and coordinating
gle-crystal X-ray diffraction analysis (Figure 2). The palla- chloride ligands was still inferior to that of the ionic com-
dium center adopts a distorted coordination geometry. The plex A with a less electron-donating PPh3 and noncoordina-
Pd–C distance of 1.956(4) Å is short compared with those ting triflate anions. The in situ formation of an ionic com-
of 1.973(2) and 1.976(3) Å observed in cis-[Pd(L)(PPh3)Cl2] plex similar to A but with PCy3 instead of the PPh3 ligand
and cis-[Pd(L)(PCy3)Cl2], respectively.[6b] The bond con- by using [Pd(L)(PCy3)Cl2] and AgOTf was anticipated to be
traction is likely due to the cationic charge of the complex. highly effective, but, somewhat surprisingly, such a catalyst
The Pd–O distance trans to the PPh3 ligand [2.136(3) Å] is system was inactive, which may be attributable to the insta-
longer than that trans to the NHC ligand [2.113(3) Å].
bility of the in situ formed catalytic species (entry 7). The
amido substituent on the ligand L of complex A was crucial
for the effectiveness of the catalyst system as the common
IMes ligand without the amido functionality did not deliver
the same level of product yield even with a higher Pd load-
ing of 5.0 mol-% (entry 8). Similarly to entries 3 and 4, the
starting material 1b was recovered.
Figure 1. Target palladium NHC complex for use in oxidative cycli-
zation.
Table 1. Screening of the palladium precatalysts.[a]
Entry PdII cat.
Pd loading
[mol-%]
Yield
[%][b]
1
2
3
4
5
6
7
8
[Pd(L)(PPh3)(H2O)2](OTf)2 (A)
2.5
10
76
51
Pd(OAc)2
Pd(OAc)2/2PPh3
PdCl2/2PPh3
[Pd(L)(PPh3)Cl2]
[Pd(L)(PCy3)Cl2]
[Pd(L)(PCy3)Cl2]/2AgOTf
PdCl2/2IMesHCl
5.0
5.0
2.5
2.5
2.5
5.0
30[c]
32[c]
0
45
0
52[c]
Figure 2. Molecular structure of the cationic portion of A. Ellip-
soids are drawn at the 50% probability level for non-hydrogen
atoms. Hydrogen atoms have been omitted for clarity. Selected
bond lengths [Å] and angles [°]: Pd1–C1 1.956(4), Pd1–P1
2.2407(10), Pd1–O1 2.136(3), Pd1–O2 2.113(3), C1–Pd1–O2
177.28(14), O1–Pd1–P1 176.21(12), C1–Pd1–P1 89.71(11), C1–
Pd1–O1 88.46(16), O2–Pd1–P1 92.60(9), O1–Pd1–O2 89.15(14).
[a] The reactions were carried out with 1-benzyl-2-(4-meth-
oxyphenyl)-1H-indole (1b; 0.16 mmol), a palladium source (2.5–
10 mol-%), diphenylacetylene (3a; 0.20 mmol), Cu(OAc)2
(0.40 mmol), and TBAB (0.32 mmol) in DMA (1 mL) for 16 h at
90 °C in sealed tubes. [b] Isolated yield. [c] Starting material 1b was
recovered.
Studies were then carried out to optimize different reac-
tion parameters (Table 2). Essentially no coupling product
was detected with commonly applied oxidants such as
Catalytic Investigation
An initial investigation was conducted to screen various CuCl2, AgOAc, and benzoquinone (BQ; entries 1–3). A
precatalysts for the benchmark reaction between the 2-aryl- good yield of 70% of the product 4ba was achieved when
indole
2-(4-methoxyphenyl)-1-(phenylmethyl)-1H-indole Cu(OAc)2 was employed as oxidant along with TBAB as
(1b) and diphenylacetylene (3a; Table 1). Complex A proved additive in DMA at 90 °C for 16 h (entry 5). Replacing
to be the most active precatalyst and a yield of 76% of the Cu(OAc)2 with Cu(OTf)2 resulted in a drastic decrease in
product could be obtained with a Pd loading of 2.5 mol-% product yield (entries 4 vs. 5). It should be noted that both
(entry 1). Using ligand-free Pd(OAc)2 as the precatalyst palladium and oxidant are necessary as no coupling prod-
gave a yield of only 51% with a 10 mol-% Pd loading (en- uct was obtained in the absence of either palladium catalyst
try 2). In addition, the use of readily available PPh3 ligands or Cu(OAc)2 (entries 5 and 7). The annulation reaction also
in combination with Pd(OAc)2 or PdCl2 was also ineffective did not proceed in the absence of TBAB (entry 6). When
and in both cases the starting material 1b was recovered K2CO3 was used as additive the desired product was
(entries 3 and 4). The ionic nature of A was crucial for the formed with 11% yield only (entry 8). The ammonium salt
catalytic activity as the neutral complex [Pd(L)(PPh3)Cl2] should function as a phase-transfer catalyst enhancing the
with coordinating chloride ligands was inactive (entry 5). solubility of an inorganic salt in organic solvent. However,
Replacing the PPh3 ligand in [Pd(L)(PPh3)Cl2] with PCy3 employing K2CO3, NaOAc, or pivalic acid as co-additive
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Construction of Polycyclic Heteroarenes
turned out to be undesirable (entries 9–11). A variety of (1a–g) reacted efficiently with diphenylacetylene (3a) to
solvents were tested; it was found that DMA and DMF provide the corresponding cyclized products in high yields
were the best reaction media (entries 5 and 12). When the (72–84%, entries 1–7), whereas substrates with electron-
solvent was switched to DMSO, a lower yield was obtained withdrawing groups (4-CN, 4-F) delivered the desired prod-
(entry 13). The yield was further diminished in toluene (en- ucts in slightly lower yields (entries 8 and 9). The aza-indole
try 14). No product was formed in acetic acid (entry 15). A derivative 1f also gave the corresponding product in good
lower yield of 48% was obtained when the reaction was yield (74%, entry 6). The catalyst system also allowed ef-
carried out at 70 °C (entry 16); elevating the bath tempera- ficient conversion of substrates 1n and 1j featuring a Cl and
ture to 110 °C, however, did not improve the product yield a Br atom, respectively, which provided the possibility for
(entry 17). Further optimization studies indicated that low- further functionalization (entries 10 and 11). Lower yields
ering the catalyst loading to 2.5 mol-% and increasing the were also observed with more hindered substrates contain-
amount of oxidant to 2.5 equiv. afforded an optimal 76% ing 3,4,5-trimethoxyphenyl and 1-naphthyl groups (en-
yield (entry 18).
tries 12 and 13). As anticipated, the cyclization reaction
with the meta-substituted arene 1m proceeded with excel-
lent site selectivity (82:18) at the less sterically hindered C–
H bond, providing the two regioisomers in a combined
yield of 81% (entry 14).
Table 2. Optimization of the reaction conditions.[a]
The generality of the method was further demonstrated
by employing various internal alkynes other than diphenyl-
acetylene as coupling partners. Pleasingly, the reaction of
symmetrical alkyne 4,4Ј-difluoro-substituted diphenylacety-
lene 3b with 1c gave the corresponding product 4cb in 76%
yield (entry 15). The oxidative annulation process exhibited
high regioselectivity when 1,4-diphenylbuta-1,3-diyne (3c)
was allowed to react with 1b (entry 16). Interestingly, when
phenylacetylene was employed in the coupling reaction with
1b, the terminal alkyne presumably underwent an initial de-
hydrogenative dimerization to form 3c, which subsequently
reacted with 1b to give 4bc as the single product in 58%
yield. Diyne 3c also reacted with sterically congested 1l to
give a high yield of inseparable regioisomers (88%, en-
try 17). No regioselectivity was observed when diyne 3c
underwent oxidative annulation with 1h; the corresponding
regioisomers 4hc and 4hcЈ were obtained in equal amounts
in an overall 73% yield (entry 18). A moderate regioselectiv-
ity was observed when 1b was coupled with the unsymmet-
rically substituted alkyne 1-methoxy-4-(2-phenylethynyl)-
benzene (3d), giving the products 4bd/4bdЈ in a modest yield
with a regioisomeric ratio of 3:1 (entry 19). Apparently,
there is no general trend in the regioselectivities in en-
tries 16–19. The alkyl,aryl-disubstituted alkyne, 1-(hex-1-
ynyl)-4-methoxybenzene, was tested as substrate, however,
the desired coupled product was not formed.
Entry Oxidant
Additives
Solvent
Yield [%][b]
1
2
CuCl2
AgOAc
TBAB
TBAB
TBAB
TBAB
TBAB
–
TBAB
K2CO3
TBAB + K2CO3 DMA
TBAB + NaOAc DMA
TBAB + PivOH DMA
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
TBAB
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMA
0
0
0
3
4
5
6
BQ
Cu(OTf)2
Cu(OAc)2
Cu(OAc)2
–
21
70 (0)[c]
0
7
0[d]
11
8
9
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
40[e]
5[f]
0
10
11
12
13
14
15
16
17
18
DMF
68
54
DMSO
Toluene
AcOH
DMA
DMA
DMA
5
0
48[g]
68[h]
76[i]
[a] Reagents and conditions: Pd catalyst A (5.0 mol-%), 1b
(0.16 mmol, 1.0 equiv.), 3a (1.2 equiv.), oxidant (2.0 equiv.), TBAB/
K2CO3 (2.0 equiv.), DMA (0.20 m), 16 h, 90 °C. [b] Isolated yield.
[c] Without Pd catalyst A. [d] Without oxidant\. [e] TBAB
(0.5 equiv.) + K2CO3 (2.0 equiv.). [f] TBAB (0.5 equiv.) + NaOAc
(2.0 equiv.). [g] 70 °C. [h] 110 °C. [i] Pd catalyst (2.5 mol-%), oxi-
dant (2.5 equiv.).
In addition to 2-arylated indoles, 3-arylated indole 2a
was also successfully utilized, producing the benzo[c]-
carbazole 5aa in 75% yield (Table 4). This protocol can also
To evaluate the scope of the catalyst system a variety of be applied to 3-arylated thiophenes. Very recently, the rho-
the nitrogen- and sulfur-containing heteroaromatic sub- dium-catalyzed dehydrogenative annulation of 3-phenyl-
strates were treated with internal alkynes under the opti- thiophenes with alkynes was introduced by Miura and Sa-
mized reaction conditions. The catalyst system showed wide toh and co-workers.[3b] In this work, the 3-arylthiophenes
substrate tolerance and high chemoselectivity with indole 2b and 2c were found to be suitable substrates, furnishing
substrates, affording benzo[a]carbazoles without the forma- the products 5ba and 5ca in yields of 91 and 53%, respec-
tion of other products (Table 3). Indoles 1 bearing different tively. The structure of 5ca was established by X-ray crystal-
protecting groups such as N-methyl, N-benzyl, or N-phenyl lographic analysis (Figure 3).
reacted smoothly to afford the desired products in yields
Pleasingly, the palladium catalyst also allowed the first
of around 75% (entries 1–3). The reaction was, however, double C–H bond activation of alkenylindole 6, giving the
complex when indole with a free NH group was employed trisubstituted carbazole derivative 7a in 65% yield
as substrate (entry 4). Electron-rich 2-arylated heterocycles (Scheme 1). Notably, Han and co-workers recently reported
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Table 3. Synthesis of benzo[a]carbazoles from the Pd-catalyzed oxidative coupling of 2-arylated indoles with alkynes.[a]
[a] Reagents and conditions: Heteroarene (0.16 mmol), alkyne (0.20 mmol), A (2.5 mol-%), Cu(OAc)2 (0.4 mmol), TBAB (0.32 mmol),
DMA (1 mL), 16 h, 90 °C, isolated yield. [b] The ratio of regioisomers was determined by the integration ratios of the Me signals in the
1H NMR spectra.
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Construction of Polycyclic Heteroarenes
Table 4. Pd-catalyzed oxidative coupling of 3-arylated heteroarenes
with diphenylacetylene (3a).
Figure 3. Molecular structure of 5ca. Ellipsoids are drawn at the
50% probability level for non-hydrogen atoms.
a similar annulation reaction in which dihydrocyclopenta-
[b]indoles were obtained as products.[7]
Next, we sought to apply our strategy to 2-arylimid-
azo[1,2-a]pyridine substrates owing to their intriguing emis-
sion properties. Employing the current protocol, 2-phenyl-
imidazo[1,2-a]pyridine (8a) was efficiently coupled with di-
phenylacetylene (3a) to provide the desired cyclized product Scheme 1. Pd-catalyzed oxidative coupling of alkenyl-substituted
indoles with diphenylacetylene.
9aa along with its tricyclic regioisomer 9aaЈ as a minor
product in an overall yield of 85% (9aa/9aaЈ = 82:18) in
just 12 h (Scheme 2). The minor product 9aaЈ is an imid- tions.[8] The two isomers were easily purified by column
azo[5,1,2-cd]indolizine, which is a rare class of heterocycle. chromatography. The selectivity of the tetra- and tricyclic
Some related compounds have previously been prepared by products was much poorer when the electron-rich and -de-
tandem [8+2] cycloaddition/[2+6+2] dehydrogenation reac- ficient symmetrical alkynes 3e and 3b were employed, the
Scheme 2. Pd-catalyzed oxidative coupling of imidazo[1,2-a]pyridine substrates with alkynes.
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Figure 4. Molecular structures of 9ab and 9aeЈ. Ellipsoids are drawn at the 50% probability level for non-hydrogen atoms.
products 9ae/9aeЈ and 9ab/9abЈ being obtained in combined generation of PdII complex B. Subsequent insertion of the
yields of 89 and 79%, respectively. The structures of 9ab alkyne into the Pd–C bond produces species C. Further C–
and 9aeЈ were confirmed by X-ray crystallography (Fig- H activation generates the major cyclopalladacycle interme-
ure 4). The selectivity was reversed when 8-methyl-2-phenyl- diate D and the minor species DЈ with the liberation of an
imidazo[1,2-a]pyridine was used as the coupling partner; acid. Reductive elimination then affords coupling products
the tricyclic regioisomer 9baЈ was obtained as the major 9aa and 9aaЈ with the Pd0 species being re-oxidized to PdII
product in a 46:54 ratio of the tetracyclic to tricyclic prod- by Cu(OAc)2. To verify this hypothesis, we conducted the
ucts. It can be anticipated that by blocking the ortho-phenyl catalytic reaction with 8-methyl-5,6-diphenylnaphtho-
CH protons, the tricyclic product could be formed selec- [1Ј,2Ј:4,5]imidazo[1,2-a]pyridine, in which the CH site next
tively. No coupling products were observed when 3-aryl- to the N atom is blocked by a Me group (Scheme 4, a). As
imidazo[1,2-a]pyridines were employed as substrates owing anticipated, a single product 9ca was isolated in pure form
to the fact that C–H activation at the 2-position of the imid- in 74% yield. The related 4-arylimidazole, 1,2-dimethyl-5-
azolyl ring is much less favorable because of the lone pair (o-tolyl)-1H-imidazole, was also used as substrate to pro-
of electrons on the vicinal N atom.[9]
duce benzimidazole 9da regioselectively, albeit in a lower
yield and with a higher catalyst loading (Scheme 4, b).
Noteworthy, the tricyclic fused ring is possible in 9Ј due to
the presence of the central sp3 N atom emanating from the
starting imidazo[1,2-a]pyridine. In contrast, for the indole
Proposed Mechanism
We have proposed a mechanism for the annulation reac- substrate, which should proceed by a similar catalytic cycle,
tion between 2-phenylimidazo[1,2-a]pyridine and an alkyne the formation of the tricyclic fused ring is impossible due
(Scheme 3). The catalytic reaction should be initiated by the to the presence of an sp2 C atom instead, which accounts
Scheme 3. Proposed mechanism for the oxidative annulation of 2-phenylimidazo[1,2-a]pyridine with an alkyne.
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Construction of Polycyclic Heteroarenes
[Pd(L)(PPh3)(H2O)2](SO3CF3)2 (A): Wet acetonitrile (10 mL) was
added to a 50 mL Schlenk flask containing [Pd(L)(PPh3)Cl2][6b]
(141 mg, 0.19 mmol) and AgOTf (97 mg, 0.38 mmol) was added.
The mixture was stirred for 12 h at ambient temperature under ni-
trogen. Once the precipitation of the insoluble AgCl salt was com-
plete, the reaction mixture was filtered through a bed of Celite and
then the solvent was completely removed under vacuum. The yel-
low sticky crude solid was washed repeatedly with diethyl ether on
a frit and dried under vacuum to give a yellow powder, yield
for the high chemoselectivity in the annulation reaction (see
Table 2).
153 mg, 80%, m.p. 202.5–204.3 °C. IR (KBr/pellet): ν = 3521 (br,
˜
w), 1689 (m), 1600 (w), 1554 (m), 1498 (m), 1438 (m), 1411 (m),
1284 (br., m), 1164 (m), 1099 (m), 1029 (s), 950 (w), 754 (m), 692
(m), 638 (s), 574 (w), 536 (m), 511 (s), 497 (m) cm–1. 1H NMR
(600 MHz, [D6]DMSO): δ = 10.40 (s, 1 H, NH), 7.62–6.99 (m, 27
H), 5.55 (d, J = 18.0 Hz, 1 H), 5.26 (d, J = 18.0 Hz, 1 H), 4.99 (d,
J = 18.0 Hz, 1 H), 4.66 (d, J = 18.0 Hz, 1 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 164.5, 138.5, 134.9, 134.0 (d, J = 10.5 Hz),
133.1, 129.9 (d, J = 11.3 Hz), 129.4 (d, J = 8.3 Hz), 129.1, 127.2,
126.5, 125.7, 124.6, 124.3, 121.1 (q, J = 321.5 Hz), 119.7, 54.0,
53.2 ppm. 31P{1H} NMR (CDCl3, 121.49 MHz): δ = 27.8 ppm.
C38H36F6N3O9PPdS2 (994.20): calcd. for C 45.90, H 3.64, N 4.22;
found C 46.04, H 3.70, N 4.01.
Scheme 4. Chemoselective Pd-catalyzed oxidative annulation reac-
tion.
1-Benzyl-2-(o-tolyl)-1H-indole (1e): A white solid, yield 228 mg,
77%, m.p. 102.0–103.8 °C. 1H NMR (300 MHz, CDCl3): δ = 7.70–
7.67 (m, 1 H), 7.29–7.21 (m, 4 H), 7.19–7.16 (m, 6 H), 6.89–6.86
(m, 2 H), 6.52 (s, 1 H), 5.15 (s, 2 H), 2.15 (s, 3 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 140.2, 138.2, 137.9, 136.8, 132.3, 131.1,
130.1, 128.7, 128.4, 128.3, 127.1, 126.4, 125.5, 121.5, 120.5, 119.9,
110.5, 102.5, 47.3, 20.1 ppm. HRMS (EI): calcd. for C22H19N
[M]+ 297.1517; found 297.1511.
Conclusions
We have successfully prepared a new ionic salt of a PdII
NHC complex that was highly efficient in catalyzing the
double C–H activation of nitrogen- and sulfur-containing
heterocyclic substrates in oxidative coupling reactions with
alkynes. A variety of heteroaromatic compounds, including
indoles, thiophenes, imidazo[1,2-a]pyridines, and imid-
azoles, can be utilized as substrates. In particular, intriguing
imidazo[5,1,2-cd]indolizine compounds have been obtained
under the reaction conditions.
1-Benzyl-2-(o-tolyl)-1H-pyrrolo[2,3-b]pyridine (1f): A colorless li-
quid, yield 192 mg, 77%. 1H NMR (300 MHz, CDCl3): δ = 8.44
(dd, J = 4.8, 1.5 Hz, 1 H), 7.96 (dd, J = 7.5, 1.5 Hz, 1 H), 7.36–
7.34 (m, 1 H), 7.28 (d, J = 7.5 Hz, 1 H), 7.23–7.21 (m, 2 H), 7.17–
7.13 (m, 4 H), 6.88 (dd, J = 5.7, 2.1 Hz, 2 H), 6.45 (s, 1 H), 5.42
(s, 2 H), 2.03 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 149.3,
143.6, 141.3, 139.0, 132.8, 131.9, 131.0, 129.9, 129.1, 129.0, 128.2,
127.9, 126.3, 121.5, 117.1, 101.3, 46.5, 20.7 ppm. HRMS (EI):
calcd. for C21H18N2 [M]+ 298.1470; found 298.1466.
Experimental Section
General: All manipulations were performed under dry nitrogen
using standard Schlenk techniques. Unless otherwise noted, all the
catalytic reactions were carried out in thick-walled sealable tubes.
All the solvents were directly used as received without any further
purification unless otherwise specified. Common starting chemicals
were purchased from commercial sources and used as received. 1H,
13C{1H}, and 31P{1H} NMR spectra, unless otherwise specified,
were recorded at 300.13, 75.48, and 121.49 MHz, respectively, using
CDCl3 as solvent and tetramethylsilane (TMS) as the internal stan-
dard. Chemical shifts are reported in ppm relative to the TMS reso-
nance (δ = 0.00 ppm) in the 1H NMR spectrum. The 1H NMR data
are reported as follows: Chemical shift, multiplicity (s = singlet, d
= doublet, t = triplet, m = multiplet, and br. = broad), coupling
constant (J) in Hz, integration. The chemical shifts in the 13C
NMR spectra are given in ppm relative to TMS using the central
peak of CDCl3 (δ = 77.0 ppm) as the internal standard. Flash
chromatography was performed by using 230–400 mesh silica gel.
ESI-MS was carried out with a sector field mass spectrometer. Ele-
mental analysis was performed with a CHNO elemental analyzer.
Emission studies were performed with a fluorescence spectropho-
tometer with a Xenon lamp as light source at room temperature.
Compounds 1a–m,[10] 2a,[11] 2b,c,[12] 8a–c,[13] and 8d[14] were synthe-
sized according to reported procedures.
General Procedure for PdII-Catalyzed Double C–H Functionaliza-
tion: Heteroarene 1 (0.16 mmol, 1.0 equiv.), Pd catalyst (2.5–
5.0 mol-%), Cu(OAc)2 (72 mg, 0.40 mmol), alkyne 3 (0.20 mmol),
and TBAB (103 mg, 0.32 mmol) in DMA (1 mL) were added to a
15 mL oven-dried sealed tube containing a stirring bar. The reac-
tion mixture was stirred at 90 °C for 16 h. Upon completion,
EtOAc was added to dilute the reaction mixture, which was then
washed with water (2ϫ 20 mL) and saturated aqueous NaCl. The
organic layer was dried with MgSO4, evaporated, and purified by
flash column chromatography on silica gel with a gradient eluent
of hexane and ethyl acetate (25:1, v/v) to afford the corresponding
cyclized product.
3-Methoxy-11-methyl-5,6-diphenyl-11H-benzo[a]carbazole (4aa): A
1
white solid, yield 47.6 mg, 72%. H NMR (300 MHz, CDCl3): δ =
8.74 (d, J = 9.3 Hz, 1 H), 7.50 (d, J = 8.4 Hz, 1 H), 7.35 (td, J =
6.9, 1.2 Hz, 1 H), 7.27–7.18 (m, 11 H), 7.05 (d, J = 2.7 Hz, 1 H),
6.91 (t, J = 9.0 Hz, 1 H), 6.62 (d, J = 9.0, Hz, 1 H), 4.43 (s, 3 H),
3.70 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 156.7, 141.0,
140.4, 139.7, 134.5, 131.7, 130.3, 130.2, 127.9, 127.6, 126.7, 126.2,
124.0, 123.7, 123.4, 121.7, 119.2, 117.0, 116.4, 115.9, 108.6, 108.3,
55.0, 34.3 ppm. The spectroscopic data match the data reported in
the literature.[3a]
Eur. J. Org. Chem. 2015, 4131–4142
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4137

H. M. Lee et al.
FULL PAPER
11-Benzyl-3-methoxy-5,6-diphenyl-11H-benzo[a]carbazole (4ba): A
136.8, 134.4, 134.2, 131.8, 131.6, 131.4, 129.9, 128.2, 127.9, 127.2,
127.0, 125.7, 125.4, 123.2, 123.1, 122.7, 122.6, 120.3, 119.9, 119.7,
light-yellow solid, yield 59 mg, 76%, m.p. 270.4–271.6 °C. 1H
NMR (300 MHz, CDCl3): δ = 8.25 (d, J = 9.3 Hz, 1 H), 7.41–7.32 109.1, 107.8, 34.5 ppm. The spectroscopic data match the data re-
(m, 6 H), 7.30–7.26 (m, 6 H), 7.24 (s, 1 H), 7.23–7.17 (m, 4 H), ported in the literature.[3a]
7.08–7.02 (m, 2 H), 6.94 (td, J = 9.0, 0.9 Hz, 1 H), 6.65 (d, J =
3-Fluoro-11-methyl-5,6-diphenyl-11H-benzo[a]carbazole (4ia): An
off-white solid, yield 46 mg, 71%. H NMR (300 MHz, CDCl3): δ
7.8 Hz, 1 H), 3.65 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
1
156.7, 141.4, 140.4, 139.6, 137.5, 135.4, 134.5, 131.7, 130.6, 130.2,
= 8.86 (dd, J = 9.3, 5.7 Hz, 1 H), 7.60 (d, J = 8.1 Hz, 1 H), 7.50–
129.2, 128.0, 127.6, 127.5, 126.8, 126.3, 126.1, 124.3, 123.7, 122.1,
7.20 (m, 11 H), 7.02 (t, J = 7.8 Hz, 1 H), 6.72 (d, J = 8.1 Hz, 1 H),
121.7, 119.8, 119.7, 116.7, 116.2, 116.1, 108.9, 108.3, 55.0,
4.50 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 161.7, 158.4,
50.1 ppm. HRMS (EI): calcd. for C36H27NO [M]+ 489.2093; found
141.1, 140.1, 139.1, 136.1, 135.3, 134.5, 134.4, 131.8, 130.1, 128.1,
489.2083.
127.8, 127.1, 126.6, 124.6, 124.5 (d, J = 6.0 Hz), 123.2, 122.0, 119.5,
114.3 (d, J = 24 Hz), 112.3 (d, J = 22 Hz), 108.9, 34.5 ppm. The
3-Methoxy-5,6,11-triphenyl-11H-benzo[a]carbazole (4ca): A light-
spectroscopic data match the data reported in the literature.[3a]
brown solid, yield 59 mg, 78%, m.p. 184.2–186.5 °C. 1H NMR
3-Chloro-11-methyl-5,6-diphenyl-11H-benzo[a]carbazole (4na): A
white solid, yield 78 mg, 61%. 1H NMR (300 MHz, CDCl3): δ =
8.72 (d, J = 9.0 Hz, 1 H), 7.67 (d, J = 4.5 Hz, 1 H), 7.54–7.51 (m,
2 H), 7.43–7.37 (m, 1 H), 7.32–7.15 (m, 10 H), 6.94 (t, J = 8.7 Hz,
1 H), 6.65 (d, J = 6.0 Hz, 1 H), 4.41 (s, 3 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 141.3, 139.9, 138.8, 136.2, 135.0, 133.9,
131.8, 130.8, 130.4, 130.1, 128.0, 127.7, 127.2, 126.9, 126.6, 125.3,
124.8, 123.6, 123.1, 122.1, 120.1, 119.6, 118.1, 108.8, 34.4 ppm. The
spectroscopic data match the data reported in the literature.[15]
(300 MHz, CDCl3): δ = 7.69–7.56 (m, 5 H), 7.43 (d, J = 9.3 Hz, 1
H), 7.31 (br. s, 5 H), 7.28–7.18 (m, 6 H), 7.09 (d, J = 8.1 Hz, 1 H),
6.99 (d, J = 2.7 Hz, 1 H), 6.93 (t, J = 7.8 Hz, 1 H), 6.87 (dd, J =
9.6, 2.7 Hz, 1 H), 6.65 (d, J = 8.1 Hz, 1 H), 3.63 (s, 3 H) ppm. 13C
NMR (75 MHz, CDCl3): δ = 156.8, 142.3, 140.3, 140.2, 139.6,
135.4, 134.3, 131.7, 130.9, 130.3, 130.2, 129.3, 128.9, 128.0, 127.6,
126.8, 126.3, 124.2, 123.9, 123.6, 121.5, 119.9, 116.9, 116.8, 116.2,
115.7, 110.0, 108.0, 55.0 ppm. HRMS (EI): calcd. for C35H25NO
[M]+ 475.1936; found 475.1931.
3-Bromo-11-methyl-5,6-diphenyl-11H-benzo[a]carbazole (4ja): A
light-brown solid, yield 51 mg, 69 %, m.p. 276.1–277.3 °C. 1H
NMR (300 MHz, CDCl3): δ = 8.67 (d, J = 9.0 Hz, 1 H), 7.83 (s, 1
H), 7.66 (dd, J = 9.0, 2.1 Hz, 1 H), 7.53 (d, J = 8.4 Hz, 1 H), 7.41
(t, J = 6 Hz, 1 H), 7.29–7.15 (m, 10 H), 6.93 (t, J = 7.8 Hz, 1 H),
6.63 (d, J = 9.0 Hz, 1 H), 4.43 (s, 3 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 141.3, 139.9, 138.7, 136.1, 134.9, 134.1, 131.7, 130.4,
130.0, 128.0, 127.9, 127.7, 126.9, 126.6, 124.8, 123.7, 123.0, 122.1,
120.3, 119.5, 119.3, 119.1, 118.1, 108.8, 34.4 ppm. HRMS (EI):
calcd. for C29H20BrN [M]+ 461.0779; found 461.0787.
11-Benzyl-1-methyl-5,6-diphenyl-11H-benzo[a]carbazole (4ea): An
off-white solid, yield 58 mg, 77%, m.p. 177.2–179.4 °C. H NMR
1
(300 MHz, CDCl3): δ = 7.53 (dd, J = 7.8, 0.9 Hz, 1 H), 7.37–7.15
(m, 19 H), 6.91 (td, J = 7.8, 1.2 Hz, 1 H), 6.62 (d, J = 8.1 Hz, 1
H), 5.54 (s, 2 H), 2.87 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 144.7, 140.0, 139.6, 139.1, 137.9, 134.3, 134.1, 132.7, 132.0,
131.7, 130.3, 128.5, 128.0, 127.6, 127.5, 127.0, 126.8, 126.7, 126.3,
126.1, 125.6, 124.8, 124.5, 122.3, 121.9, 120.7, 120.6, 112.8, 54.9,
23.6 ppm. HRMS (EI): calcd. for C36H27N [M]+ 473.2143; found
473.2140.
2,3,4-Trimethoxy-11-methyl-5,6-diphenyl-11H-benzo[a]carbazole
(4ka): A white solid, yield 50 mg, 65%, m.p. 216.6–218.2 °C. 1H
NMR (300 MHz, CDCl3): δ = 8.03 (s, 1 H), 7.51 (d, J = 8.4 Hz, 1
H), 7.39 (td, J = 7.2, 1.2 Hz, 1 H), 7.28–7.25 (m, 2 H), 7.18–7.13
(m, 6 H), 7.11–7.02 (m, 2 H), 6.91 (td, J = 7.2, 0.9 Hz, 1 H), 6.47
(d, J = 8.1 Hz, 1 H), 4.47 (s, 3 H), 4.14 (s, 3 H), 3.93 (s, 3 H), 3.28
(s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 151.7, 151.4, 142.8,
141.9, 140.4, 135.2, 134.7, 128.6, 127.7, 126.4, 126.1, 124.8, 124.5,
123.6, 123.4, 123.2, 123.0, 122.0, 119.6, 119.3, 118.9, 118.2, 108.8,
98.8, 60.9, 60.7, 55.9, 34.5 ppm. HRMS (EI): calcd. for C32H27NO3
[M]+ 473.1991; found 473.1998.
11-Benzyl-1-methyl-5,6-diphenyl-11H-benzo[g]pyrido[2,3-b]indole
(4fa): A light-brown solid, yield 56 mg, 74%, m.p. 212.5–214.8 °C.
1H NMR (300 MHz, CDCl3): δ = 8.36 (t, J = 3.6 Hz, 1 H), 7.52
(d, J = 6.0 Hz, 1 H), 7.44 (d, J = 6.9 Hz, 1 H), 7.34 (d, J = 7.2 Hz,
1 H), 7.30–7.22 (m, 10 H), 7.06–7.05 (m, 3 H), 6.86–6.81 (m, 4 H),
5.86 (s, 2 H), 2.99 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
155.3, 145.0, 139.5, 139.2, 137.8, 137.3, 134.2, 133.0, 132.7, 131.9,
131.7, 131.4, 130.2, 129.5, 128.4, 128.1, 128.0, 127.6, 127.0, 126.8,
126.4, 125.6, 125.4, 122.5, 119.0, 118.9, 116.5, 52.6, 23.1 ppm.
HRMS (EI): calcd. for C35H26N2 [M]+ 474.2096; found 474.2090.
13-Methyl-7,8-diphenyl-13H-naphtho[1,2-a]carbazole (4la): An off-
white solid, yield 51 mg, 73%. H NMR (300 MHz, CDCl3): δ =
3-tert-Butyl-11-methyl-5,6-diphenyl-11H-benzo[a]carbazole (4ga): A
light-orange solid, yield 59 mg, 84 %, m.p. 265.1–267.3 °C. 1H
NMR (300 MHz, CDCl3): δ = 8.79 (d, J = 9.3 Hz, 1 H), 7.72–7.70
(m, 2 H), 7.53 (d, J = 8.1 Hz, 1 H), 7.39 (t, J = 7.2 Hz, 1 H), 7.30–
7.25 (m, 10 H), 6.95 (t, J = 7.5 Hz, 1 H), 6.67 (d, J = 7.8 Hz, 1 H),
4.46 (s, 3 H), 1.32 (s, 9 H) ppm. 13C NMR (75.4 MHz, CDCl3): δ
= 147.4, 141.1, 140.5, 139.7, 135.2, 134.8, 132.8, 131.8, 131.2, 130.3,
127.9, 127.4, 126.7, 126.2, 124.2, 123.9, 123.3 (2 C), 121.9 (2 C),
119.9, 119.2, 117.4, 108.7, 34.8, 34.3, 31.2 ppm. HRMS (EI): calcd.
for C33H29N [M]+ 439.2302; found 439.2296.
1
8.82 (d, J = 8.1 Hz, 1 H), 8.00 (d, J = 7.8 Hz, 1 H), 7.78–7.72 (m,
2 H), 7.67–7.63 (m, 3 H), 7.49 (t, J = 7.5 Hz, 1 H), 6.80 (d, J =
9.0 Hz, 1 H), 7.34 (m, 10 H), 7.07 (t, J = 7.5 Hz, 1 H), 6.82 (d, J
= 7.8 Hz, 1 H), 3.91 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ
= 146.1, 140.0, 139.5, 139.3, 135.3, 132.3, 131.9, 130.9, 130.2, 128.4,
128.2, 128.0, 127.6, 126.9, 126.4, 126.2, 126.0, 125.9, 125.5, 125.3,
124.8, 122.3, 122.1, 120.3, 117.3, 110.9, 37.9 ppm. The spectro-
scopic data match the data reported in the literature.[3a]
2-Methoxy-11-methyl-5,6-diphenyl-11H-benzo[a]carbazole (4ma):
The typical catalytic procedure was followed using 2-(3-meth-
oxyphenyl)-1-methyl-1H-indole (1m; 59 mg, 0.25 mmol,
1.00 equiv.) and diphenylacetylene (3a; 53 mg, 0.3 mmol) as start-
ing materials. Purification by column chromatography (hexane/
11-Methyl-5,6-diphenyl-11H-benzo[a]carbazole-3-carbonitrile (4ha):
A white solid, yield 44 mg, 68%. H NMR (300 MHz, CDCl3): δ
= 8.89 (d, J = 9.0 Hz, 1 H), 8.12 (s, 1 H), 7.75 (dd, J = 9.0, 3.0 Hz,
1 H), 7.60 (d, J = 9.0 Hz, 1 H), 7.49 (t, J = 7.2 Hz, 1 H), 7.35–7.32
(m, 4 H), 7.29–7.28 (m, 2 H), 7.26–7.24 (m, 2 H), 7.20–7.17 (m, 2
1
EtOAc, 25:1) furnished 4ma (68 mg, 66% yield) as an off-white
1
H), 7.01 (t, J = 9.0 Hz, 1 H), 6.72 (d, J = 8.1 Hz, 1 H), 4.48 (s, 3 solid. H NMR (300 MHz, CDCl3): δ = 8.19 (d, J = 2.4 Hz, 1 H),
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 141.8, 139.4, 138.1, 7.63 (d, J = 9.3 Hz, 1 H), 7.51 (d, J = 8.4 Hz, 1 H), 7.38 (dt, J =
4138
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Eur. J. Org. Chem. 2015, 4131–4142

Construction of Polycyclic Heteroarenes
7.2, 1.2 Hz, 1 H), 7.28–7.18 (m, 10 H), 7.11 (dd, J = 9.6, 2.7 Hz, 1
H), 6.92 (dt, J = 7.8, 0.9 Hz, 1 H), 6.65 (d, J = 7.8 Hz, 1 H), 4.46
solid. Combined yield: 53 mg, 73%, m.p. 225.1–227.5 °C. 1H NMR
(300 MHz, CDCl3, mixture): δ = 9.07 (d, J = 1.5 Hz, 1 H), 9.00 (d,
(s, 3 H), 4.01 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 156.8, J = 9.0 Hz, 1 H), 8.74 (dd, J = 9.0, 4.8 Hz, 2 H), 8.18 (d, J =
141.4, 140.3, 139.7, 134.6, 132.7, 131.8, 131.1, 130.4, 130.0, 127.9,
127.5, 126.7, 126.2, 124.5, 123.2, 122.8, 122.1, 119.2, 118.3, 115.2,
108.8, 103.3, 55.5, 34.2 ppm. The spectroscopic data match the data
reported in the literature.[3a]
1.5 Hz, 1 H), 7.74 (dd, J = 8.7, 1.5 Hz, 1 H), 7.67 (dd, J = 7.8,
1.8 Hz, 1 H), 7.63–7.56 (m, 13 H), 7.51–7.46 (m, 2 H), 7.41–7.27
(m, 10 H), 7.06 (t, J = 7.5 Hz, 1 H), 6.97 (d, J = 6.9 Hz, 1 H), 4.37
(s, 3 H), 4.36 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3, mixture):
δ = 141.7, 141.6, 141.5, 139.4, 138.4, 136.5, 134.1, 134.0, 133.8,
131.6, 131.4, 131.3, 131.2, 131.0, 129.6, 128.6, 128.5, 128.4, 128.2,
128.1, 127.9, 126.2, 126.1, 126.0, 125.8, 123.5, 123.4, 123.3, 123.2,
123.1, 123.0, 122.5, 122.3, 122.2, 120.4, 120.3, 120.1, 119.7, 119.5,
119.4, 116.9, 112.7, 109.2, 109.1, 108.6, 108.0, 98.4, 97.8, 88.4, 86.7,
34.3, 34.2 ppm. HRMS (EI): calcd. for C32H20N2 [M]+ 432.1626;
found 432.1635.
4-Methoxy-11-methyl-5,6-diphenyl-11H-benzo[a]carbazole (4maЈ):
The typical catalytic procedure was followed using 1m (59 mg,
0.25 mmol, 1.0 equiv.) and 3a (53 mg, 0.3 mmol) as starting materi-
als. Purification by column chromatography (hexane/EtOAc, 50:1)
furnished 4maЈ (15 mg, 15 % yield) as a white solid. 1H NMR
(300 MHz, CDCl3): δ = 8.45 (d, J = 9.0 Hz, 1 H), 7.55–7.49 (m, 2
H), 7.37 (t, J = 9.0 Hz, 1 H), 7.24–7.23 (m, 4 H), 7.16–7.13 (m, 2
H), 7.08–7.06 (m, 3 H), 7.03–7.00 (m, 1 H), 6.90–6.86 (m, 2 H),
11-Benzyl-3-methoxy-6-(4-methoxyphenyl)-5-phenyl-11H-benzo[a]-
6.44 (d, J = 8.1 Hz, 1 H), 4.44 (s, 3 H), 3.36 (s, 3 H) ppm. 13C carbazole and 11-Benzyl-3-methoxy-5-(4-methoxyphenyl)-6-phenyl-
NMR (75 MHz, CDCl3): δ = 158.0, 143.9, 141.8, 140.5, 130.4, 11H-benzo[a]carbazole (4bd and 4bdЈ, 75:25): A light-brown solid.
130.2, 127.7, 126.4, 125.9, 125.1, 124.6, 124.5, 122.1, 119.3, 115.3,
108.8, 107.0, 55.8, 34.8 ppm. The spectroscopic data match the data
reported in the literature.[3a]
Combined yield: 56 mg, 68 %, m.p. 222.0–224.5 °C. 1H NMR
(300 MHz, CDCl3, major + minor): δ = 8.24 (d, J = 9.3 Hz, 1.4
H), 7.40–7.28 (m, 11.5 H), 7.25–7.23 (m, 3.94 H), 7.21–7.17 (m, 5
H), 7.10–6.94 (m, 4 H), 6.85–6.74 (m, 4 H), 6.00 (s, 2.6 H), 3.82 (s,
3 H, major), 3.77 (s, 1.1 H, minor), 3.65 (s, 1.1 H, minor), 3.64 (s,
3 H, major) ppm. 13C NMR (75 MHz, CDCl3, major + minor): δ
= 158.3, 156.7, 141.4, 139.8, 137.5, 135.4, 134.5, 132.7, 131.7, 131.2,
130.2, 129.1, 128.0, 127.7, 127.6, 126.2, 126.1, 124.3, 123.8, 123.7,
121.8, 119.8, 117.1, 116.2, 116.1, 116.0, 113.4, 113.1, 108.9, 108.3,
55.1, 55.0, 50.1 ppm. HRMS (EI): calcd. for C37H29NO2 [M]+
519.2198; found 519.2205.
5,6-Bis(4-fluorophenyl)-3-methoxy-11-phenyl-11H-benzo[a]carb-
azole (4cb): An off-white solid, yield 62 mg, 76 %, m.p. 320.8–
321.7 °C. 1H NMR (300 MHz, CDCl3): δ = 7.71–7.68 (m, 3 H),
7.58 (dd, J = 6.3, 1.8 Hz, 2 H), 7.45 (dd, J = 9.0, 1.5 Hz, 1 H),
7.29–7.25 (m, 3 H), 7.19–7.13 (m 3 H), 7.08–6.89 (m, 7 H), 6.72 (d,
J = 7.8 Hz, 1 H), 3.67 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 156.9, 142.3, 140.1, 136.1, 135.5, 135.4, 134.6, 134.3, 133.1 (d,
J = 7.5 Hz), 131.7 (d, J = 7.9 Hz), 130.3, 130.0, 129.2, 129.1, 124.4,
124.0, 123.4, 121.3, 120.1, 116.2, 115.9, 115.3, 115.0, 114.9, 114.6,
1-Methoxy-7-methyl-5,6-diphenyl-7H-benzo[c]carbazole (5aa): An
110.2, 107.8, 55.0 ppm. HRMS (EI): calcd. for C35H23F2NO [M]+ off-white solid, yield 49 mg, 75%, m.p. 259.0–261.0 °C. H NMR
1
511.1748; found 511.1743.
(300 MHz, CDCl3): δ = 8.98 (d, J = 8.4 Hz, 1 H), 7.45–7.40 (m, 2
H), 7.30 (t, J = 9.0 Hz, 1 H), 7.25 (br. s, 3 H), 7.22–7.16 (m, 6 H),
7.13–7.12 (m, 1 H), 7.10–7.07 (m, 3 H), 4.18 (s, 3 H), 3.26 (s, 3
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 155.5, 141.7, 140.1,
139.2, 138.6, 137.4, 131.4, 131.3, 130.5, 127.4, 127.3, 126.9, 126.8,
126.2, 124.1, 123.9, 122.9, 121.5, 121.0, 119.0, 117.9, 114.9, 108.7,
106.5, 55.3, 32.9 ppm. HRMS (EI): calcd. for C30H23NO [M]+
413.1780; found 413.1768.
11-Benzyl-3-methoxy-5-phenyl-6-(2-phenylethynyl)-11H-benzo[a]-
carbazole or 11-Benzyl-3-methoxy-6-phenyl-5-(2-phenylethynyl)-
11H-benzo[a]carbozole (4bc or 4bcЈ): A brown solid, yield 66 mg,
1
81%, m.p. 138.1–140.2 °C. H NMR (300 MHz, CDCl3): δ = 9.02
(d, J = 7.8 Hz, 1 H), 8.20 (d, J = 9.3 Hz, 1 H), 7.57–7.55 (m, 4 H),
7.52–7.50 (m, 1 H), 7.47–7.46 (m, 2 H), 7.41–7.35 (m, 3 H), 7.31
(br. s, 6 H), 7.29–7.26 (m, 3 H), 7.12 (d, J = 2.7 Hz, 1 H), 7.05 (dd,
J = 9.3, 2.7 Hz, 1 H), 5.99 (s, 2 H), 3.68 (s, 3 H) ppm. 13C NMR 1-Methyl-5,6-diphenylbenzo[b]naphtho[1,2-d]thiophene (5ba): An
1
(75 MHz, CDCl3): δ = 156.7, 145.1, 141.3, 140.0, 137.3, 136.2, off-white solid, yield 58 mg, 91%, m.p. 195.0–196.8 °C. H NMR
135.3, 133.8, 131.3, 129.2, 128.3, 128.2, 128.1, 128.0, 127.6, 127.2,
126.0, 125.0, 123.7, 123.5, 121.6, 120.3, 117.0, 116.8, 116.1, 115.6,
109.0, 108.0, 97.2, 89.3, 55.1, 49.9 ppm. HRMS (EI): calcd. for
C38H27NO [M]+ 513.2093; found 513.2101.
(300 MHz, CDCl3): δ = 8.14 (d, J = 8.1 Hz, 1 H), 7.86 (d, J =
7.8 Hz, 1 H), 7.56 (d, J = 7.8 Hz, 2 H), 7.49 (td, J = 7.2, 1.2 Hz, 1
H), 7.40 (t, J = 8.7 Hz, 2 H), 7.30–7.25 (m, 8 H), 7.21–7.18 (m, 2
H), 2.87 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 142.7,
141.9, 139.6, 138.8, 137.3, 137.2, 133.8, 133.3, 133.0, 132.8, 131.3,
130.1, 129.7, 129.2, 128.0, 127.7, 127.4, 127.3, 126.8, 125.6, 124.9,
13-Methyl-7-phenyl-8-(2-phenylethynyl)-13H-naphtho[1,2-a]carb-
azole and 13-Methyl-8-phenyl-7-(2-phenylethynyl)-13H-naphtho[1,2-
a]carbazole (4lc and 4lcЈ, 54:46): An orange solid. Combined yield:
124.8, 123.3, 122.4, 24.3 ppm. HRMS (EI): calcd. for C29H20
S
[M]+ 400.1286; found 400.1283.
1
64 mg, 88%. H NMR (300 MHz, CDCl3, mixture): δ = 9.33 (d, J
= 3.0 Hz, 1 H), 8.94 (d, J = 6.0 Hz, 1 H), 8.80 (t, J = 9.0 Hz, 2 H),
7-Fluoro-4,5-diphenylnaphtho[2,1-b]thiophene (5ca): An off-white
8.14–8.11 (m, 2 H), 8.05 (d, J = 3.0 Hz, 2 H), 7.92 (d, J = 9.0 Hz, solid, yield 30 mg, 53%, m.p. 147.1–149.2 °C. 1H NMR (300 MHz,
2 H), 7.77–7.66 (m, 16 H), 7.61–7.46 (m, 12 H), 7.34 (t, J = 7.5 Hz,
CDCl3): δ = 8.39 (dd, J = 9.0, 5.7 Hz, 1 H), 8.02 (d, J = 6.0 Hz, 1
1 H), 7.27 (d, J = 6.9 Hz, 1 H), 3.89 (s, 3 H), 3.88 (s, 3 H) ppm. H), 7.59 (d, J = 5.4 Hz, 1 H), 7.39–7.30 (m, 2 H), 7.27–7.23 (m, 8
13C NMR (75.4 MHz, CDCl3, mixture): δ = 146.2, 146.0, 140.1, H), 7.18–7.16 (m, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
140.0, 139.3, 137.4, 132.4, 132.3, 131.9, 131.6, 131.4, 130.5, 130.3,
128.6, 128.5, 128.4, 128.3, 128.2, 128.1, 128.0, 127.9, 127.8, 127.5,
127.4, 126.5, 126.3, 126.2, 126.1, 126.0, 125.6, 125.5, 124.9, 124.5,
123.9, 122.4, 121.0, 120.9, 118.4, 117.4, 115.5, 113.7, 111.2, 111.1,
97.9, 97.1, 89.5, 88.6, 37.9, 37.8 ppm. HRMS (EI): calcd. for
C35H23N [M]+ 457.1830; found 457.1822.
162.1, 158.8, 139.6, 138.3, 135.3, 134.9, 131.8, 131.4, 129.9, 128.0,
127.9, 127.3 (d, J = 8.0 Hz), 127.0, 125.9, 125.7, 122.1, 115.8, 115.5,
111.9, 111.6 ppm. HRMS (EI): calcd. for C24H15FS [M]+ 354.0878;
found 354.0870.
3-(4-Methoxyphenyl)-9-methyl-1,2-diphenyl-9H-carbazole (7a): A
1
light-brown solid, yield 45 mg, 65%, m.p. 176–178.1 °C. H NMR
11-Methyl-5-phenyl-6-(2-phenylethynyl)-11H-benzo[a]carbazole- (300 MHz, CDCl3): δ = 7.62 (d, J = 8.4 Hz, 2 H), 7.32–7.21 (m, 11
3-carbonitrile and 11-Methyl-6-phenyl-5-(2-phenylethynyl)-11H-
benzo[a]carbazole-3-carbonitrile (4hc and 4hcЈ, 52:48): An orange
H), 7.06 (t, J = 6.9 Hz, 1 H), 6.98 (d, J = 8.7 Hz, 2 H), 6.92–6.86
(m, 3 H), 3.88 (s, 3 H), 3.49 (s, 3 H) ppm. 13C NMR (75 MHz,
Eur. J. Org. Chem. 2015, 4131–4142
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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4139

H. M. Lee et al.
FULL PAPER
CDCl3): δ = 159.8, 150.9, 143.2, 141.9, 135.6, 135.0, 134.7, 133.3,
5,6-Di-p-tolylnaphtho[1Ј,2Ј:4,5]imidazo[1,2-a]pyridine (9ae): The
132.1, 131.4, 131.2, 130.8, 129.9, 128.2, 127.6, 127.3, 126.6, 123.0,
typical catalytic procedure was followed using 2-phenylimidazo[1,2-
120.7, 120.1, 119.9, 114.0, 111.0, 109.7, 55.4, 31.2 ppm. HRMS a]pyridine (8a; 49 mg, 0.25 mmol, 1.0 equiv.) and 3e (62 mg,
(EI): calcd. for C32H25NO [M]+ 439.1936; found 439.1932.
0.30 mmol, 1.2 equiv.) as staring materials with a reaction time of
12 h. Purification by column chromatography (hexane/EtOAc,
20:1) furnished 9ae (53 mg, 89% combined yield) as a light-brown
5,6-Diphenylnaphtho[1Ј,2Ј:4,5]imidazo[1,2-a]pyridine (9aa): The typ-
ical catalytic procedure was followed using 2-phenylimidazo[1,2-a]-
pyridine (8a; 49 mg, 0.25 mmol, 1.0 equiv.) and diphenylacetylene
(3a; 53 mg, 0.30 mmol) as starting materials with a reaction time
of 12 h. Purification by column chromatography (hexane/EtOAc,
20:1) furnished 9aa (64 mg, 85% combined yield) as a light-brown
1
solid, m.p. 289.5–290.5 °C. H NMR (300 MHz, CDCl3): δ = 8.94
(dd, J = 8.4, 0.6 Hz, 1 H), 7.82 (d, J = 9.3 Hz, 1 H), 7.68 (t, J =
9 Hz, 1 H), 7.60 (d, J = 7.8 Hz, 1 H), 7.47 (t, J = 6.9 Hz, 1 H),
7.31–7.24 (m, 2 H), 7.12 (s, 4 H), 7.06 (s, 4 H), 6.49 (td, J = 6.9,
1.2 Hz, 1 H), 2.37 (s, 3 H), 2.32 (s, 3 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 148.0, 140.7, 137.2, 135.9, 135.6, 134.0, 133.7, 131.7,
131.4, 130.2, 129.2, 128.3, 127.6, 127.1, 126.7, 126.6, 126.1, 126.0,
122.9, 117.8, 110.5, 21.3, 21.2 ppm; two carbon signals were miss-
ing due to signal overlap. HRMS (EI): calcd. for C29H22N2 [M]+
398.1783; found 398.1778.
1
solid, m.p. 221.5–222.9 °C. H NMR (300 MHz, CDCl3): δ = 8.97
(d, J = 9.0 Hz, 1 H), 7.84 (d, J = 9 Hz, 1 H), 7.69 (t, J = 6.9 Hz,
1 H), 7.60 (d, J = 8.1 Hz, 1 H), 7.49 (td, J = 8.1, 0.9 Hz, 1 H),
7.32–7.20 (m, 12 H), 6.48 (t, J = 6.6 Hz,1 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 148.0, 140.8, 138.6, 136.9, 133.6, 131.6,
131.5, 130.4, 128.8, 128.5, 128.2, 127.7, 127.6, 127.5, 127.3, 126.6,
126.5, 126.2 (2 C), 126.1, 123.0, 117.8, 110.7 ppm. HRMS (EI):
calcd. for C27H18N2 [M]+ 370.1470; found 370.1474.
2-Phenyl-3,4-di-p-tolylimidazo[5,1,2-cd]indolizine (9aeЈ): The typical
catalytic procedure was followed using 2-phenylimidazo[1,2-a]pyr-
idine (8a; 49 mg, 0.25 mmol, 1.0 equiv.) and 3e (62 mg, 0.30 mmol)
as starting materials with a reaction time of 12 h. Purification by
column chromatography (hexane/EtOAc, 25:1) furnished 9aeЈ
(35 mg, 89 % combined yield) as a yellow solid, m.p. 223.8–
224.1 °C. 1H NMR (300 MHz, CDCl3): δ = 8.02–7.99 (m, 1 H),
7.93 (d, J = 5.1 Hz, 2 H), 7.83 (d, J = 6.6, Hz, 2 H), 7.36–7.24 (m,
7 H), 7.16 (t, J = 9.0 Hz, 4 H), 2.41 (s, 3 H), 2.38 (s, 3 H) ppm.
13C NMR (75 MHz, CDCl3): δ = 150.7, 139.9, 137.9, 136.7, 133.7,
131.9, 131.5, 131.1, 131.0, 130.9, 130.0, 129.7, 129.4, 129.2 (2 C),
128.3, 127.2, 126.8, 124.3, 112.6, 111.1, 21.4, 21.3 ppm. HRMS
(EI): calcd. for C29H22N2 [M]+ 398.1783; found 398.1775.
2,3,4-Triphenylimidazo[5,1,2-cd]indolizine (9aaЈ): The typical cata-
lytic procedure was followed using 2-phenyimidazo[1,2-a]pyridine
(8a; 49 mg, 0.25 mmol, 1.0 equiv.) and diphenylacetylene (3a;
53 mg, 0.30 mmol) as starting materials with a reaction time of
12 h. Purification by column chromatography (hexane/EtOAc,
25:1) furnished 9aaЈ (14 mg, 85% combined yield) as a yellow solid,
1
m.p. 209.6–210.8 °C. H NMR (300 MHz, CDCl3): δ = 8.05–8.02
(m, 1 H), 7.95–7.93 (m, 2 H), 7.81 (d, J = 6.9 Hz, 2 H), 7.46–7.24
(m, 13 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 140.0, 134.0,
133.9, 133.6, 131.7, 131.6, 131.0, 130.2, 129.7, 129.4, 128.6, 128.5,
128.4, 128.2, 127.3, 127.1, 127.0, 112.8, 111.4 ppm; two carbon sig-
nals are missing due to signal overlap. HRMS (EI): calcd. for
C27H18N2 [M]+ 370.1470; found 370.1479.
11-Methyl-5,6-diphenylnaphtho[1Ј,2Ј:4,5]imidazo[1,2-a]pyridine
(9ba): The typical catalytic procedure was followed using 8-methyl-
2-phenylimidazo[1,2-a]pyridine (8b; 52 mg, 0.25 mmol, 1.0 equiv.)
and 3a (53 mg, 0.30 mmol) as starting materials with a reaction
time of 12 h. Purification by column chromatography (hexane/
EtOAc, 20:1) furnished 9ba (38 mg, 88% combined yield) as an off-
white solid, m.p. 241.5–243.0 °C. 1H NMR (300 MHz, CDCl3): δ
= 9.03 (d, J = 8.1 Hz, 1 H), 7.68 (dt, J = 8.1, 1.2 Hz, 1 H), 7.48
(dt, J = 8.1, 1.6 Hz, 1 H), 7.32–7.29 (m, 3 H), 7.24–7.14 (m, 8 H),
7.08 (d, J = 6.6 Hz, 1 H), 6.39 (t, J = 6.9 Hz, 1 H), 2.80 (s, 3
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 148.6, 140.7, 138.8,
137.1, 133.4, 131.7, 131.3, 130.5, 128.4, 127.6 (2 C), 127.5, 126.7,
126.5, 126.4, 126.3, 125.9, 125.6, 124.3, 123.2, 110.5, 17.7 ppm; two
carbon signals were missing due to signal overlap. HRMS (EI):
calcd. for C28H20N2 [M]+ 384.1626; found 384.1628.
5,6-Bis(4-fluorophenyl)naphtho[1Ј,2Ј:4,5]imidazo[1,2-a]pyridine
(9ab): The typical catalytic procedure was followed using 2-phenyl-
imidazo[1,2-a]pyridine (8a; 49 mg, 0.25 mmol, 1.0 equiv.) and 3b
(64 mg, 0.30 mmol) as starting materials with a reaction time of
12 h. Purification by column chromatography (hexane/EtOAc,
20:1) furnished 9ab (54 mg, 79% combined yield) as an off-white
1
solid, m.p. 299.2–301.0 °C. H NMR (300 MHz, CDCl3): δ = 8.95
(d, J = 7.8 Hz, 1 H), 7.84 (d, J = 9.0 Hz, 1 H), 7.70 (t, J = 6.6 Hz,
1 H), 7.57–7.50 (m, 2 H), 7.33 (br. s, 2 H), 7.24–7.18 (m, 2 H),
7.13–7.02 (m, 4 H), 6.95 (t, J = 8.7 Hz, 2 H), 6.55 (t, J = 6.6 Hz,
1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 162.2 (d, J =
246.7 Hz), 161.7 (d, J = 244.5 Hz), 148.2, 134.4, 134.3 133.1, 133.0,
132.8, 132.1 131.9, 131.4, 127.4 (d, J = 2.3 Hz), 126.4 (d, J =
4.4 Hz), 126.3, 126.2, 125.8, 123.1, 118.1, 115.9, 115.6, 114.9, 114.6,
110.9 ppm. HRMS (EI): calcd. for C27H16F2N2 [M]+ 406.1282;
found 406.1286.
7-Methyl-2,3,4-triphenylimidazo[5,1,2-cd]indolizine (9baЈ): The typi-
cal catalytic procedure was followed using 8-methyl-2-phenylimid-
azo[1,2-a]pyridine (8b; 52 mg, 0.25 mmol, 1.0 equiv.) and 3a
(53 mg, 0.30 mmol) as starting materials with a reaction time of
12 h. Purification by column chromatography (hexane/EtOAc,
25:1) furnished 9baЈ (46 mg, 88% combined yield) as a yellow solid,
3,4-Bis(4-fluorophenyl)-2-phenylimidazo[5,1,2-cd]indolizine (9abЈ):
The typical catalytic procedure was followed using 2-phenylimid-
azo[1,2-a]pyridine (8a; 49 mg, 0.25 mmol, 1.0 equiv.) and 3b
(64 mg, 0.30 mmol) as starting materials with a reaction time of
12 h. Purification by column chromatography (hexane/EtOAc,
25:1) furnished 9abЈ (26 mg, 79% combined yield) as a yellow solid,
1
m.p. 210.1–212.4 °C. H NMR (300 MHz, CDCl3): δ = 7.89 (d, J
= 9.0 Hz, 1 H), 7.83 (d, J = 6.0 Hz, 2 H), 7.78 (d, J = 9.0 Hz, 1
H), 7.49 (d, J = 9.0 Hz, 2 H), 7.44–7.35 (m, 8 H), 7.33–7.32 (m, 2
H), 7.29–7.28 (m, 1 H), 3.07 (s, 3 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 149.6, 139.6, 134.3, 134.2, 133.9, 131.1, 130.6, 130.2,
130.1, 129.7, 129.0, 128.6, 128.4, 128.3, 128.0, 127.9, 127.1, 126.9,
124.6, 122.9, 112.8, 29.7 ppm. HRMS (EI): calcd. for C28H20N2
[M]+ 384.1626; found 384.1629.
1
m.p. 211.5–212.1 °C. H NMR (300 MHz, CDCl3): δ = 8.03 (dd, J
= 7.5, 0.9 Hz, 1 H), 7.97–7.88 (m, 2 H), 7.79 (dd, J = 7.8, 1.6 Hz,
2 H), 7.34–7.29 (m, 7 H), 7.10–7.02 (m, 4 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 162.7 (d, J = 246.7 Hz), 162.1 (d, J =
245.8 Hz), 151.1, 140.0, 133.5, 132.8, 131.8, 131.7, 131.5, 130.3,
129.7 (d, J = 4.1 Hz), 129.6 (d, J = 2.3 Hz), 128.5, 127.1, 126.3,
8-Methyl-5,6-diphenylnaphtho[1Ј,2Ј:4,5]imidazo[1,2-a]pyridine (9ca):
The typical catalytic procedure was followed using 5-methyl-2-
124.0, 115.9 (d, J = 7.3 Hz), 115.7, 115.6, 112.6, 111.6 ppm. HRMS phenylimidazo[1,2-a]pyridine (60 mg, 0.29 mmol, 1.0 equiv.) and 3a
(EI): calcd. for C27H16F2N2 [M]+ 406.1282; found 406.1280.
(62 mg, 0.34 mmol) as starting materials with a reaction time of
4140
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Eur. J. Org. Chem. 2015, 4131–4142

Construction of Polycyclic Heteroarenes
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12 h. Purification by column chromatography (hexane/EtOAc,
23:2) furnished 9ca (82 mg, 74%) as an off-white solid, m.p. 277.8–
1
278.9 °C. H NMR (300 MHz, CDCl3): δ = 8.98 (d, J = 8.1 Hz, 1
H), 7.75 (d, J = 9.0 Hz, 1 H), 7.67 (t, J = 7.8 Hz, 1 H), 7.53–7.43
(m, 2 H), 7.31–7.23 (m, 4 H), 7.14–7.00 (m, 7 H), 6.43 (d, J =
6.9 Hz, 1 H), 1.67 (s, 3 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
150.5, 143.0, 141.0, 140.1, 139.8, 133.5, 131.7, 131.6, 131.3, 128.0,
127.7 (2 C), 127.5, 127.3, 126.8, 126.4 (2 C), 126.1, 126.0, 124.5,
123.1, 115.4, 113.2, 23.1 ppm. HRMS (EI): calcd. for C28H20N2
[M]+ 384.1626; found 384.1634.
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1,2,9-Trimethyl-4,5-diphenyl-1H-naphtho[1,2-d]imidazole (9da): The
typical catalytic procedure was followed using 1,2-dimethyl-5-(o-
tolyl)-1H-imidazole (47 mg, 0.25 mmol, 1.0 equiv.) and 3a (53 mg,
0.30 mmol) as starting materials with a reaction time of 12 h. Puri-
fication by column chromatography (hexane/EtOAc, 4:1) furnished
9da (50 mg, 55%) as an off-white solid, yield 32 mg, 55%, m.p.
1
257.8–258.5 °C. H NMR (300 MHz, CDCl3): δ = 7.38–7.32 (m, 2
H), 7.24 (br. s, 1 H), 7.21–7.14 (m, 8 H), 7.12–7.10 (m 2 H), 3.29
(s, 3 H), 3.09 (s, 3 H), 2.62 (s, 3 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 149.4, 139.8, 138.5, 137.7, 134.8, 134.6, 131.5, 131.1,
130.6, 130.3, 127.9, 127.4, 127.3, 127.0, 126.2, 125.8, 125.5, 125.3,
123.7, 32.5, 24.3, 14.6 ppm. HRMS (EI): calcd. for C26H22N2
[M]+ 362.1783; found 362.1778.
[3]
[4]
X-ray Diffraction Studies: Data were collected at 150(2) K with a
Bruker APEX II diffractometer equipped with a CCD area detec-
tor and a graphite monochromator utilizing Mo-Kα radiation (λ =
0.71073 Å). The unit cell parameters were obtained by least-squares
refinement. Data collection and reduction was performed by using
the Bruker APEX2 and SAINT software[16] and absorption correc-
tions were made by using the SADABS program.[17] All the struc-
tures were solved by direct methods and refined by full-matrix le-
ast-squares methods against F2 with the SHELXTL software pack-
age.[18] All the non-hydrogen atoms were refined anisotropically
and all the hydrogen atoms were fixed at calculated positions and
refined by using a riding model. The crystallographic data are pre-
sented in Table S1 in the Supporting Information.
[5]
[6]
CCDC-917931 (for A), -917933 (for 5ca), -917932 (for 9ab), and
-1030617 (for 9aeЈ) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see footnote on the first page of this arti-
cle): Additional catalytic tables, procedures for the preparation of
starting materials, NMR spectra for all products, emission spectra
of 9aa, 9ab, 9ba, 9aaЈ, 9abЈ, and 9baЈ, and crystallographic data for
A, 5ca, 9ba, and 9aeЈ.
[7]
[8]
T. Su, X. Han, X. Lu, Tetrahedron Lett. 2014, 55, 27–30.
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The authors are grateful to the Ministry of Science and Technology
of Taiwan for financial support of this work. The authors declare
no competing financial interest.
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Received: March 31, 2015
Published Online: May 19, 2015
4142
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Eur. J. Org. Chem. 2015, 4131–4142