Synthesis of 2-Phosphaindolizine and [1,3]Azaphospholo[1,5-a]quinoline

Article abstract of DOI:10.1002/ejic.201501120

The reaction of (chloromethyl)dichlorophosphine (1) with 2-[(trimethylsilyl)methyl]pyridine (6) and 2-[(trimethylsilyl)methyl]quinoline (12) in THF affords unsubstituted parent 2-phosphaindolizine (5) and [1,3]azaphospholo[1,5-a]quinoline (7). Multinuclear low-temperature NMR spectroscopy was used to investigate the reaction mechanism; a cascade of substitution and cyclization steps involving transient picolylphosphines and phosphorus heterocycles was identified. The molecular and crystal structures of two heterocyclic intermediates and of 7 were determined by single-crystal X-ray diffraction. Moreover, all intermediates and products were characterized by multinuclear ¹H, ¹³C and ³¹P NMR spectroscopy.

Full text of DOI:10.1002/ejic.201501120

DOI: 10.1002/ejic.201501120
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CLUSTER
ISSUE
Heterophospholes
Synthesis of 2-Phosphaindolizine and [1,3]Azaphospholo[1,5-
a]quinoline
Christina Hettstedt,[a] Robert J. Mayer,[a] Jörn F. Martens,[a] Sarah Linert,[a] and
Konstantin Karaghiosoff*[a]
Dedicated to Professor Dr. Paul Knochel on the occasion of his 60th birthday
Abstract: The reaction of (chloromethyl)dichlorophosphine (1) tion and cyclization steps involving transient picolylphosphines
with 2-[(trimethylsilyl)methyl]pyridine (6) and 2-[(trimethyl- and phosphorus heterocycles was identified. The molecular and
silyl)methyl]quinoline (12) in THF affords unsubstituted parent crystal structures of two heterocyclic intermediates and of 7
2-phosphaindolizine (5) and [1,3]azaphospholo[1,5-a]quinoline were determined by single-crystal X-ray diffraction. Moreover,
(7). Multinuclear low-temperature NMR spectroscopy was used all intermediates and products were characterized by multinu-
1
to investigate the reaction mechanism; a cascade of substitu- clear H, 13C and 31P NMR spectroscopy.
Introduction
A synthesis starting from N-alkylpyridinium salts and PCl3 in-
volving the intermediacy of a PCl2-substituted pyridinium ylide
was published in 1999 by Bansal et al.[3] This synthesis demon-
strates an impressive predilection for 2-phosphaindolizine gen-
eration. An overview of existing synthetic approaches to, and
chemical properties of, 2-phosphaindolizines inclusive of their
1-aza, 3-aza and 1,3-diaza derivatives has been recently pub-
lished.[4]
All synthetic methods described in the literature afford 2-
phosphaindolizines with substituents at the two positions adja-
cent to phosphorus. The parent 2-phosphaindolizine is not ac-
cessible by these routes and its synthesis remains a challenge.
A convenient reagent for introduction of a –CH=P– unit in
aromatic five-membered phosphorus heterocycles is (chloro-
methyl)dichlorophosphine (1). This reagent contains two adja-
cent reactive electrophilic sites with slightly different reactivi-
ties. [3 + 2] Cyclocondensation of 1 with 2-aminopyridine (2)
and related 2-amino azines and 2-amino azoles provides a gen-
eral synthetic approach to anellated 1,4,2-diazaphospholes with
unsubstituted carbon atoms adjacent to phosphorus. This
route was first published by Schmidpeter and co-workers
(Scheme 3).[5]
2-Phosphaindolizines have been known since 1991 and were
first prepared by Schmidpeter and Bansal.[1] Different synthetic
approaches have been described; all rely heavily on C–H activa-
tion. In the synthetic route proceeding through a [4 + 1]-cyclo-
condensation a dialkylpyridinium halide is reacted with PCl3 in
the presence of a base (e.g. triethylamine) to give the 2-phos-
phaindolizine scaffold (Scheme 1).[1] The starting material needs
an electron-withdrawing substituent R2 to activate the adjacent
CH2 group.
Scheme 1. [4 + 1]-Cyclocondensation in the synthesis of 2-phosphaindol-
izines. R1: H, Me, Ph, p-C6H4Cl; R2: COPh, COtBu, CO2Me, CO2Et, CN, p-
C6H4NO2, Ph; R3: H, Me, Et, Bu; X: Hal.[1]
In 1992 the Regitz group published a synthesis of 2-phos-
phaindolizines which proceeds via [3 + 2]-cycloaddition of an
azomethine ylide with a phosphaalkyne (Scheme 2).[2]
Scheme 3. [3 + 2]-Cyclocondensation of 2-aminopyridine (2) and (chloro-
methyl)dichlorophosphine (1) gives the unsubstituted skeleton of the anel-
ated 1,4,2-diazaphosphole (3).
Scheme 2. [3 + 2]-Cycloaddition route to 2-phosphaindolizines.[2]
[a] Department of Chemistry, Ludwig Maximilians University (LMU)
Butenandtstrasse 5–13 (Haus D), 81377 München, Germany
E-mail: klk@cup.uni-muenchen.de
In the first step (chloromethyl)dichlorophosphine (1) reacts
with the amino group of 2-aminopyridine (2) to form a diazadi-
phosphetidine. In the second step involving the chloromethyl
function, the diazaphosphole ring is closed and, following loss
www.cup.uni-muenchen.de
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/ejic.201501120.
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of HCl, the diazaphospholo-pyridine 3 is formed as the only
product.[5]
Salts 8 and 9 were isolated as colourless to bright yellow
solids in moderate yields (57 %, 8; 48 %, 9). Compound 8 was
found to be nearly insoluble in common aprotic organic sol-
vents and decomposed in H2O and other protic solvents. Com-
pound 9 was found to be soluble in polar aprotic organic sol-
vents like THF, MeCN and DCM and both 8 and 9 were charac-
Using 2-methylpyridine (4) instead of 2-aminopyridine (2) in
the analogous reaction with ClCH2PCl2 (1) might offer a possi-
ble route to unsubstituted parent 2-phosphaindolizine (5).
However, the reduced reactivity of the pyridine resulting from
NH2 replacement with a methyl could make formation of the
first P–C bond even more difficult. The use of 2-(trimethyl-
silyl)methyl pyridine (PicTMS, 6) can foreseeably overcome this
problem; 6 is known to easily form P–C bonds upon reaction
with diphenyl chlorophosphine.[6] This concept was used for
the scaffold of 2-methylpyridine. Here we describe the synthesis
1
terized by 31P, H and 13C NMR spectroscopies. The molecular
and crystal structures of both compounds were investigated by
single-crystal X-ray diffraction. In the case of 9, structures of
two polymorphs differing in the conformation of the cation,
were determined.
Unexpectedly, the success in forming 8 and 9 turned out to
and characterization of parent heterocycles 2-phosphaindoliz- be strongly dependent upon reaction temperature. Reaction of
ine (5) and 1,3-azaphospholo[1,5-a]quinoline (7). Intermediates, ClCH2PCl2 (1) with 2 equiv. PicTMS (6) in THF at room tempera-
indicating a possible mechanism for formation of these hetero- ture afforded only traces of 2-phosphaindolizine (5) as revealed
cycles were identified and, in some cases, withstood isolation. by 31P NMR analysis of the reaction mixture. Additionally, traces
Based on these results, a mechanism for the formation of of the chlorophosphine 10 could be detected. The predomina-
heterocycles 5 and 7 can be readily envisioned.
ting precipitate formed under these conditions turned out to
be 2-picoline hydrochloride (Scheme 5).
Results and Discussion
Syntheses
[1,3]Azaphospholo[1,5-a]pyridine (5)
In contrast to the reaction of (chloromethyl)dichlorophosphine
(1) with 2-aminopyridine (2) the corresponding reaction with 2-
methylpyridine (4) in THF or MeCN failed to result in azaphos-
phole ring formation. As expected, the reactivity of 4 is insuffi-
cient to enable P–C bond formation. Introduction of SiMe3 in
place of a hydrogen atom in the methyl group of 2-picoline (4)
has been reported to enable P–C bond formation.[6] In this con-
text, as well as for our studies on the synthesis of bis(picolyl)-
phosphines,[7] we investigated the reaction of 2-[(trimethyl-
silyl)methyl]pyridine (PicTMS, 6) with 1 at 0 °C in different molar
ratios.
When ClCH2PCl2 (1) was allowed to react with an equimolar
amount of 6 and the reaction warmed to ambient temperature
2-chloro-2,3-dihydro-1H-[1,3]azaphospholo[1,5-a]pyridin-4-ium
chloride (8) precipitated from the reaction solution. The use of
2 equiv. PicTMS (6) under the same reaction conditions lead to
precipitation of the corresponding salt 9 (R = Pic). (Chloro-
methyl)picolylphosphines 10 (R = Cl) and 11 (R = Pic) were
always observed as byproducts upon 31P NMR analyses of the
remaining solution (Scheme 4). Nevertheless it was impossible
to isolate 10 and 11 under these reaction conditions. Notably,
following complete removal of solvent, phosphines 10 and 11
could no longer be observed by NMR.
Scheme 5. The reaction of (chloromethyl)dichlorophosphine (1) with 2 equiv.
PicTMS (6) at ambient temperature leads to a variety of products.
We postulate that compound 8 is likely formed in the first
step and the second equivalent of PicTMS (6) functions as a
base to eliminate HCl thus yielding heterocycle 5. Notably, un-
der these conditions, PicTMS appears to serve as a dibasic moi-
ety forming both picoline hydrochloride and TMSCl.
To obtain 2-phosphaindolizine (5) quantitatively the syn-
thetic route detailed above was optimized. The reaction tem-
perature was raised to refluxing conditions to accelerate the
cyclization reaction. Additionally, the second equivalent of
PicTMS (6) was replaced with commercially available trimethyl-
amine (TEA). These changes lead to quantitative conversion of
the starting materials to desired product 2-phosphaindolizine
(5) (Scheme 6). The elimination of HCl was quite slow and the
reaction took about 24 h to complete.
Scheme 6. Synthesis of the parent 2-phosphaindolizine.
Parent 2-phosphaindolizine (5) was barely soluble in pentane
and Et2O. Due to this limitation, extractive workup of this crude
reaction was not possible with these solvents. Compound 5 was
soluble in more polar solvents like THF, MeCN and DCM, as is
the byproduct triethylammonium chloride. As a result, 5 was
Scheme 4. Reaction of (chloromethyl)dichlorophosphine (1) with PicTMS (6).
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always co-isolated with HNEt3Cl. Compound 5 could be identi- ate yield (56 %) and was characterized by multinuclear (1H, 31P,
fied and characterized by 1H, 13C and 31P NMR spectroscopic 13C) NMR spectroscopy and single-crystal X-ray diffraction stud-
analyses.
ies.
[1,3]Azaphospholo[1,5-a]quinoline (7)
Mechanistic Investigations
Formation of the 1,3-azaphosphole ring from cyclocondensa-
tion of ClCH2PCl2 (1) and PicTMS (6) could be extended to the
corresponding quinaldinylTMS derivative (QuinTMS, 12). Reac-
tion of ClCH2PCl2 (1) with 2 equiv. QuinTMS (12) at 0 °C lead
to the formation of the heterophosphole 1,3-azaphospholo[1,5-
a]quinoline (7) and quinaldine hydrochloride. Notably, bis-
(quinaldinyl)phosphine 13 could not be observed under these
reaction conditions (Scheme 7). The driving force for generation
of 7 is so high that, even with equimolar amounts of 1 and 12,
product 7 is formed quantitatively.
To obtain more detailed insight into the reactions discussed
above and to explain the different reactivities and product dis-
tributions at different temperatures with the two different silyl
species 6 and 12, low temperature NMR studies were carried
out.
Reaction of Chloromethyl Dichlorophosphine (1) with
PicTMS (6)
For the experimental setup, 2.3 equiv. PicTMS (6) were added
to 1.0 equiv. (chloromethyl)dichlorophosphine (1) at –78 °C and
the mixture directly placed into the NMR spectrometer where
it was warmed up directly to 0 °C.
At 0 °C continuous progress of the reaction could be moni-
tored in the 31P{1H} NMR spectra (Figure 1) which involved two
clearly defined phosphine species besides the starting material
1 (δP = 161.0). Picolyl chloro phosphine 10 (δP = 91.4 ppm) was
the initially formed intermediate; reaction of 10 with the sec-
ond equivalent of PicTMS (6) was found to generate bis(pic-
olyl)phosphine 11 (δP = –12.6 ppm).
Scheme 7. Reaction of (chloromethyl)dichlorophosphine (1) with QuinTMS
(12).
When the reaction was complete and no more PicTMS (6)
1,3-Azaphospholo[1,5-a]quinoline (7) was soluble in apolar was present, precipitation was observed and attributed to the
and polar aprotic organic solvents like pentane, DCM or chloro- formation of picolylphospholane 9. If only 1 equiv. PicTMS was
form. Good solubility in pentane enabled almost complete sep- used, reaction progress was found to stop at chlorophosphine
aration of 7 from quinaldine hydrochloride. Azaphosphole 7 10 although this compound cyclizes in a slow subsequent reac-
was isolated as a moisture sensitive pale yellow solid in moder- tion to form salt 8 (Scheme 8). Both intermediate phosphines
Figure 1. Stacked plot of the different 31P{1H} NMR spectra obtained at 0 °C from the reaction of 1 with PicTMS (6).
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1
10 and 11 could be identified and characterized by in situ H, NMR Data
13C and 31P NMR spectroscopy at 0 °C.
Figure 2 shows the specific numbering of atoms in compounds
7–11, 13 and 14 for the assignment of NMR spectroscopic data
discussed here. Compounds 2-phosphaindolizine (5) and aza-
phospholoquinoline 7 show a chemical shift in their respective
31P NMR spectra which is lowfield shifted [δP = 120.6 ppm (5),
115.7 ppm (7)] compared to the characteristic region of substi-
tuted 2-phosphaindolizines (131–184 ppm).[1] The coupling
constants of the phosphorus over two bonds to the adjacent
protons are, in all four cases, very similar (37.1–37.9 Hz) despite
the different chemical shifts of protons H1 [8.30 ppm (5),
9.05 ppm (7)] and H2 [7.23 ppm (5), 7.33 ppm (7)]. Coupling
constants are comparable to the 2JPH coupling constants of mo-
nosubstituted 2-phosphaindolizines from the literature.[1]
Scheme 8. Overview of the reactivity of (chloromethyl)dichlorophosphine (1)
with PicTMS (6) starting at 0 °C.
Reaction of (Chloromethyl)dichlorophosphine (1) with
QuinTMS (12)
For low temperature NMR experiments evaluating the reaction
of 1.0 equiv. (chloromethyl)dichlorophosphine (1) with
2.0 equiv. of QuinTMS (12), both substances were combined
at – 100 °C and transferred to the pre-cooled spectrometer. Due
to the higher reactivity of this system relative to the reaction of
1 with PicTMS (6), spectral measurements were performed at
–40 °C.
Figure 2. Specific numbering of atoms for the assignment of NMR spectro-
scopic data for compounds 5, 7–11, 13 and 14. For salts 8 and 9 the same
numbering scheme for the carbon atoms as for compound 5 is valid.
The 31P NMR chemical shifts of chlorine-substituted interme-
diates 10 (δ =91.4 ppm) and 14 (δ =90.8 ppm) can be found in
the characteristic region for chlorophosphines. The 31P NMR sig-
nal of the cyclic chlorophosphine 8 (δ = 68.7 ppm) is lowfield
shifted compared to acyclic intermediates 10 and 14. A similar
trend can be found for phosphine intermediates 11, 13 and 9.
The 31P NMR signal of cyclic phosphine 9 (–26.9 ppm) is low-
field shifted relative to the analogous signal of acyclic deriva-
tives 11 (–12.6 ppm) and 13 (–12.8 ppm).
At –40 °C the observed reaction progress and products [14
(δP = 90.8 ppm), 13 (δP = –12.8 ppm)] were comparable to
the products found in the reaction discussed above (Scheme 9,
Figure 1; see also Supporting Information, Figure 1). Both inter-
1
mediates 14 and 13 could be identified by in situ H, 13C and
31P NMR spectroscopy at –40 °C.
The CH2 protons of the CH2Ar groups of phosphine interme-
diates 11 and 13 and the CH2 groups of the five membered
ring in 9 are diastereotopic and show the AB part of an ABX
1
2
coupling pattern (X = 31P) in the H NMR spectrum. The JHH
coupling constants are 13.6 Hz (11, 13) and 15.4 Hz (9). In all
three spectra the protons show different coupling constants to
2
2
phosphorus. The JPH1 and JPH2 coupling in heterocycle 9 is
quite large (21.2, 18.6 Hz) compared to the same coupling con-
stants in phosphines 11 (2.0 Hz) and 13 (0.7 Hz).
Scheme 9. Overview of the reaction of QuinTMS (12) with (chloromethyl)di-
chlorophosphine (1) at –40 °C.
Following formation of chlorophosphine 14, the reaction
showed a temperature dependence starting at lower tempera-
tures than those found when studying the reaction of 1 and
PicTMS (6). Even at 0 °C, intramolecular cyclization of chloro-
Crystal Structures
[1,3]Azaphospholo[1,5-a]quinoline (7)
phosphine 14 seemed to be favored to generate heterocycle Single crystals suitable for X-ray diffraction of 7 were obtained
15 which could not be observed spectroscopically (Scheme 9). by recrystallization from pentane. Azaphospholoquinoline 7
Consequently, the second equivalent of QuinTMS (12) was crystallizes in the monoclinic space group P21/c with four for-
found to act as a base, leading to facile generation of [1,3]aza- mula units in the unit cell. The asymmetric unit consists of one
phospholo[1,5-a]quinoline (7) under these conditions.
molecule of 7 (Figure 3).
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parallel to the b-axis. These chains are interconnected by the
noted C–H···C(π) interactions and form layers parallel to the ab-
plane (Figure 5).
Table 2. Non-classical hydrogen bonds in the crystal structure of 7.
C–H···Cg
C–H
H···Cg
C···Cg
C–H···Cg
γ
7
C1–H1···Cg(3)a
0.95(3)
2.72(3) 3.515(4)
2.70(3) 3.397(4)
142.0(2)
131.0(2)
2.4
8.7
C5–H5···Cg(2)b 0.95(3)
Symmetry codes: 7: a (1 – x, –0.5 + y, 1.5 – z), b (2 – x, 0.5 + y, 1.5 – z); Cg
is the center of gravity of the aromatic rings d(H···Cg) < 3.0 Å, γ < 30.0°.
Cg(2) is the ring N1–C7, Cg(3) is the ring C6–C11.
Figure 3. Diamond drawing of the asymmetric unit of [1,3]azaphospholo[1,5-
a]quinoline (7). Thermal ellipsoids are drawn at a 50 % probability level.
The molecular structure is completely planar with a C1–P1–
C2 bond angle of 89.1(1)° (Table 1) which is slightly smaller
than the corresponding angle (91.9°) in the only literature
known crystal structure of a substituted 2-phosphaindolizine
derivative.[8] The lengths of the two P–C bonds in 7 are clearly
different [d(P1–C1) = 1.703(3) Å, d(P1–C2) = 1.730(3) Å] and
their values lie within the range of a P–C single (1.87 Å)[9] and
a P=C double bond (1.67 Å). The difference of the lengths be-
tween the two P–C bonds is larger in literature than in the
structure of 7 obtained herein.
Table 1. Selected bond lengths [Å] and angles [°] in the crystal structure of
7.
P1–C1
P1–C2
N1–C3
N1–C1
N1–C7
C2–C3
1.703(3)
1.730(3)
1.401(4)
1.367(4)
1.423(3)
1.373(4)
C1–P1–C2
P1–C1–N1
P1–C2–C3
N1–C3–C2
C1–N1–C3
89.1(1)
114.3(2)
113.5(2)
111.2(3)
111.9(2)
The N1–C3 bond in the molecular structure of 7 [1.401(4) Å]
is longer than the N1–C1 bond [1.367(4) Å] whereas both N–C
bonds are clearly longer than the literature value of a CAr–N–C2
bond (1.371 Å).[10]
In the crystal structure of 7 the molecules are interconnected
by non-classical C–H···C(π) hydrogen bonds [d(C1···Cg(3)) =
3.515(4) Å, d(C5···Cg(2)) = 3.397(4) Å]. Here, every molecule acts
as hydrogen-bond donor and -acceptor at the same time (Fig-
ure 4, Table 2). Moreover, π-stacking interactions between the
molecules can be found which causes the formation of chains
Figure 5. View along the c-axis on several unit cells of 7. Thermal ellipsoids
are drawn at a 50 % probability level.
2-Chloro-2,3-dihydro-1H-[1,3]azaphospholo[1,5-a]pyridin-4-
ium Chloride (8)
Single crystals of 8 suitable for X-ray diffraction were obtained
by slow evaporation of the solvent (CHCl3). Compound 8 crys-
tallizes in the orthorhombic space group Pnma with four for-
mula units and four disordered solvent molecules (CHCl3) in
the unit cell. The molecular structure of 8 consists of twice the
asymmetric unit. Due to symmetry considerations the positions
of C4 and N1 are statistically half-occupied (Figure 6).
In the molecular structure of 8 the P–C bond length
[1.845(3) Å] is slightly shorter than the literature value (1.87,
1.855 Å)[9,10] for a P–C single bond (Table 3). The C–P–C angle
[89.7(1)°] is in the range of the corresponding angle in the mo-
lecular structure of 7 (Table 4).
The bonding situation around the phosphorus atom is re-
markable. The P1–Cl1 bond [2.105(1) Å] is clearly longer than
literature values for a P–Cl bond (2.04, 2.008 Å)[9,10] whereas the
Figure 4. Layers parallel to the ab-plane formed by non classical C–H···C(π)-
hydrogen bonds and π-stacking interactions. Symmetry codes: a (1 – x, –0.5
+ y, 1.5 – z), b (2 – x, 0.5 + y, 1.5 – z), c (x, 1 + y, z), d (x, –1 + y, z). Thermal
ellipsoids are drawn at a 50 % probability level.
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2-(Pyridin-2-ylmethyl)-2,3-dihydro-1H-
[1,3]azaphospholo[1,5-a]pyridin-4-ium Chloride (9)
Single crystals suitable for X-ray diffraction of the salt 9 could
be obtained by slow evaporation of the solvent from a concen-
trated solution of 9 in THF. By this method two polymorph
molecular- and crystal structures of 9 could be obtained.
In the first molecular structure (structure 1) the picolyl sub-
stituent at phosphorus and the phosphacycle point away from
each other, whereas in the other structure (structure 2) both
heterocycles are arranged almost parallel to each other and
interact via intramolecular π-stacking (Figure 8).
Figure 6. Molecular structure of 8 including one disordered solvent molecule
(CHCl3). Symmetry codes: a (x, 0.5 – y, z), b (x, 1.5 – y, z). Thermal ellipsoids
are drawn at a 50 % probability level.
Table 3. Selected bond lengths [Å] and angles [°] in the crystal structure of
8.
P1–C1
1.845(3)
C1–P1–C1a
C1–P1–Cl1
89.6(1)
97.7(9)
P1–Cl1
P1···Cl3
2.105(1)
3.274(1)
Symmetry code: a (x, 0.5 – y, z).
Table 4. Distances [Å] and angles [°] of the non classical C–H···Cl hydrogen
bond and the Cl···C(π) halogen bond in the crystal structure of 8.
Figure 8. Asymmetric units of the crystals structures of 9. Left: structure 1,
right: structure 2. Thermal ellipsoids are drawn at a 50 % probability level.
C–H···Cl
C–H
H···Cl
C···Cl
C–H···Cl
160.1(2)
C–Cl···C(π)
174.6(1)
C5–H5A···Cl3c
C–Cl···C(π)
C5–Cl2···C3f
0.96(5)
C–Cl
2.52(5)
Cl···C(π)
3.337(1)
3.434(3)
Structure 1 crystallizes in the monoclinic space group C2/c
with eight formula units in the unit cell. Structure 2 crystallizes
in the monoclinic space group P21/c with four formula units in
the unit cell. The asymmetric unit of structure 1 consists of one
molecule of cation 9 and two half-occupied chloride ions. The
asymmetric unit of structure 2 is composed of one formula unit
of 9.
Within the two structures, the lengths of the P1–C1 and P1–
C2 bonds are very similar. In structure 1 the length of the P1–
C8 bond is shorter than the other two P–C bonds, whereas the
P1–C8 bond in structure 2 is longer (Table 5). All P–C atom
1.742(1)
Symmetry codes: c (x, y, 1 + z), f (0.5 – x, 1 – y, 0.5 + z).
chloride counterion (Cl3) coordinates from the opposite side to
the phosphorus with a Cl1–P1–Cl3 angle of 176.5(1)°. The P1–
Cl3 distance [3.274(1) Å] is still clearly smaller than the sum of
the van-der-Waals radii of the involved atoms [ΣrvdW(P–Cl) =
3.55 Å][11] and the structure may be seen as analogous to an
SN2 transition state (Figure 7).
In the crystal, molecules of 8 interact with the solvent mole- distances in the molecular structures of 9 are shorter than the
cules via Cl2···C(π) halogen bonds [d(Cl···C(π)) = 3.337(1) Å]. literature value for P–C single bonds (1.87 Å).[9] Both C1–P1–C2
These adducts form chains parallel to the c-axis by C5–H5A···Cl3 angles [88.4(9), 89.3(8)°] are very similar to the values found in
interactions [d(C5···Cl3) = 3.434(3) Å] (Figure 7).
the molecular structures of compounds 7 and 8.
Figure 7. Chains parallel to the c-axis in the crystal structure of 8. Symmetry codes: c (x, y, 1 + z), d (x, y, –1 + z), e (0.5 – x, 1 – y, 0.5 + z), f (0.5 – x, 1 – y, 0.5
+ z). Thermal ellipsoids are drawn at a 50 % probability level.
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Table 5. Selected bond lengths [Å] and angles [°] in the crystal structure of
9.
In the crystal structure of 9 (structure 2) the molecules form
chains parallel to the b-axis by C4–H4···N2 [d(C4···N2) =
3.356(1) Å] hydrogen bonds. C–H···Cl hydrogen bonds connect
these chains to form layers parallel to the ab-plane (Figure 10,
Table 6). The layers are interconnected by π-stacking interac-
tions {d[Cg(3)···Cg(3)] = 4.158(2) Å, Cg(3) contains N2} stacked
along the c-axis (Figure 11). All C–H···Cl hydrogen bonds in the
crystal structure of 9 are in the same range [d(C···Cl) between
3.492(1) and 3.681(2) Å] and comparable with the C–H···Cl hy-
drogen bonds in the crystal structure of compound 8.
Struct. 1
Struct. 2
Struct. 1
Struct. 2
P1–C1
P1–C2
P1–C8
1.855(1)
1.858(2)
1.847(2)
1.843(2)
1.840(2)
1.854(2)
C1–P1–C2
C1–P1–C8
C2–P1–C8
88.4(9)
100.2(8)
96.6(8)
89.3(8)
101.2(9)
102.2(9)
In the crystal structure of 9 (structure 1) the molecules form
dimers, interconnected by non-classical C–H···C(π) hydrogen
bonds between the C6–H6 bond of the annulated six-mem-
bered ring and the π-system of the picolyl moiety of an adja-
cent molecule [d(C6···Cg(3)) = 3.532(1) Å]. The formation of the
dimers is also governed by C–H···Cl1 hydrogen bonds. Those
interactions, together with C–H···Cl2 hydrogen bonds intercon-
nect the dimers to form tubular chains parallel to the c-axis
that enclose the Cl1 atoms (Table 6, Figure 9).
Table 6. Distances [Å] and angles [°] of the non-classical C–H···Cl hydrogen
bonds and the Cl···C(π) halogen bonds in the crystal structure of 9.
Struct. 1 C–H···Cg
C6–H6···Cg(3)a
C–H
0.90(1) 2.72(1)
C–H H···Cl
H···Cg
C···Cg
C–H···Cg
151.0(1)[a]
C–H···Cl
3.532(1)
C···Cl
C–H···Cl
C2–H2A···Cl2b
C7–H7···Cl1
C8–H8A···Cl1
0.99(1) 2.88(1)
0.94(1) 2.64(1)
0.95(1) 2.68(1)
3.541(1)
3.514(1)
3.591(2)
124.9(2)
155.4(2)
160.2(2)
Struct. 2 C–H···Cl/N
C–H
H···Cl/N
C···Cl
C–H···Cl
C4–H4···N2b
C5–H5···Cl1a
C7–H7···Cl1c
0.95(1) 2.46(1)
0.92(1) 2.73(1)
0.89(1) 2.65(1)
3.356(1)
3.600(1)
3.492(1)
156.3(2)
158.3(2)
158.9(2)
Figure 10. Layers parallel to the ab-plane in the crystal structure of 9 (struc-
ture 2). Symmetry codes: a (–1 + x, y, z), b (0.5 – x, –0.5 + y, 1.5 – z), c (0.5 –
x, 0.5 + y, 1.5 – z), d (–0.5 – x, 0.5 + y, 1.5 – z), e (–0.5 – x, –0.5 + y, 1.5 – z).
Thermal ellipsoids are drawn at a 50 % probability level.
Symmetry codes, structure 1: a (1 – x, –y, 1 – z), b (1 – x, 1 – y, 1 – z); struc-
ture 2: a (–1 + x, y, z), b (0.5 – x, –0.5 + y, 1.5 – z), c (0.5 – x, 0.5 + y,
1.5 – z). Cg is the center of gravity of the aromatic rings d(H···Cg) < 3.0 Å,
γ < 30.0°. Cg(3) is the ring N2–C13.
[a] γ = 4.8.
Figure 11. π-Stacking interactions in the crystal structure of 9 (structure 2),
d(Cg(3)–Cg(3)d) = 4.158(2) Å, Cg(3) obtains N2. Symmetry code: f (1 – x, 2 – y,
2 – z). Thermal ellipsoids are drawn at a 50 % probability level.
Conclusions
We have presented the synthesis of parent 2-phosphaindolizine
(5) and azaphospholoquinoline (7) by reaction of (chloro-
methyl)dichlorophosphine (1) with silylated 2-picoline deriva-
tives. This new synthetic approach for the preparation of 2-
phosphaindolizine derivatives differs from currently established
methods. The two new compounds are the first in 1- and 3-
position unsubstituted representatives of 2-phosphaindolizines.
Figure 9. Non-classical C–H···C(π) and C–H···Cl hydrogen bonds in the crystal
structure of 9 (structure 1). Symmetry code: a (1 – x, –y, 1 – z), b (1 – x, 1 –
y, 1 – z), c (x, –1 + y, z). Thermal ellipsoids are drawn at a 50 % probability
level.
Eur. J. Inorg. Chem. 2016, 726–735
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109.3651 MHz (31P), a Bruker Avance 400 operating at 400.18 MHz
(1H), 100.64 MHz (13C) and 162.00 MHz (31P) or using a Bruker Av-
ance 400TR operating at 400.13 MHz (1H), 100.62 MHz (13C) and
161.98 MHz (31P). Chemical shifts are referenced to Me4Si (1H, 13C)
and 85 % H3PO4 (31P) as external standards. All spectra were meas-
ured, if not mentioned otherwise, at 25 °C. Coupling constants are
given in Hz.
Due to the protons in the 1- and 3-positions the chemical shift
of the 31P NMR signal of both compounds is shifted lowfield
relative to the signals of substituted derivatives. The crystal
structure of azaphospholoquinoline (7) is governed by weak C–
H···π hydrogen bonds and π-stacking.
The progress of the reaction of 1 with silylated picoline deriv-
atives 6 and 12 was investigated in detail by low temperature
31P NMR spectroscopy whereupon key intermediates could be
identified. The identity of two such intermediates, the dihydro-
azaphospholopyridinium chlorides 8 and 9 could be confirmed
by single-crystal X-ray diffraction studies.
Mass Spectrometry: Mass spectrometry data were obtained using
a JEOL JMS-700 Mstation spectrometer using the direct EI or DEI
mode for neutral compounds and the FAB mode for ionic com-
pounds with 4-nitrobenzyl alcohol as a matrix.
X-ray Crystallography: The molecular structures in the crystalline
state were determined using an Oxford Xcalibur3 diffraction instru-
ment equipped with a Spellman generator (voltage 50 kV, current
40 mA) and a Kappa CCD detector, operating with Mo-Kα radiation
(λ = 0.71073 Å). The data collection was performed with the CrysAlis
CCD software[12] and the data reduction with the CrysAlis RED soft-
ware.[13] The structure was solved with SIR-92 or SIR-2004,[14] re-
fined with SHELXL-97[15] and finally checked using PLATON.[16] Ab-
sorption correction using the SCALE3 ABSPACK multiscan me-
thod[17] was applied. All relevant data and parameters for the X-
ray data collection and structure refinement are given in Table 7.
Hydrogen atoms involved in hydrogen bonding were located in the
difference Fourier map and refined isotropically.
Experimental Section
General: All reactions were carried out under an inert gas atmos-
phere using Schlenk techniques. Argon (Messer Griesheim, purity
4.6 in a 50-L steel cylinder) was used as inert gas. Glass vessels were
stored in a 130 °C drying oven and were flame-dried in 10–3 mbar
vacuum before use. Starting materials 1, 6 and 12 were prepared
according to established literature procedures.[5–7] All other chemi-
cals were commercially available and were used as received. The
solvents were dried using commonly known drying methods and
were freshly distilled before use.
NMR Spectroscopy: NMR spectra were recorded either with a JEOL
EX 400 Eclipse instrument operating at 400.128 MHz (1H),
100.626 MHz (13C) and 161.835 MHz (31P), a JEOL EX 270 Eclipse
CCDC 1428869 (for 7), 1428870 (for 8), 1428871 (for 9 – structure
1), and 1428872 (for 9 – structure 2) contain the supplementary
crystallographic data for this paper. These data can be obtained
instrument operating at 270.1661 MHz (1H), 67.9395 MHz (13C) and free of charge from The Cambridge Crystallographic Data Centre.
Table 7. Crystal structure data of compounds 7–9.
7
8
9 (structure 1)
9 (structure 2)
Formula
M
C11H8NP
185.15
C8H9Cl5NP
327.38
C13H14ClN2P
264.68
C13H14ClN2P
264.68
T [K]
173(2)
173(2)
173(2)
173(2)
Color, habit
Crystal size [mm]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
colorless plate
0.38 × 0.10 × 0.03
monoclinic
P21/c (No. 14)
7.8675(6)
6.1738(5)
18.5336(13)
90
yellow block
0.20 × 0.15 × 0.10
orthorhombic
Pnma
16.4230(6)
8.7720(3)
9.2310(3)
90
yellow block
0.35 × 0.20 × 0.10
monoclinic
C2/c
19.1430(7)
12.0740(4)
11.3460(4)
90
yellow block
0.25 × 0.21 × 0.17
monoclinic
P21/n (No. 14)
9.0894(4)
13.7843(6)
10.5644(5)
90
ꢀ [°]
94.537(7)
90
897.40(12)
4
1.370
0.250
90
90
109.167(4)
90
2477.06(15)
8
1.419
0.415
94.381(4)
90
1319.76(10)
4
1.332
0.390
γ [°]
V [Å3]
Z
1329.84(8)
4
1.635
ρcalcd [g cm–3
]
μ [mm–1
]
1.178
Irradiation, Mo-Kα [Å]
F(000)
0.71073
384
0.71073
656
0.71073
1104
0.71073
552
Index ranges
–9 ≤ h ≤ 9
–7 ≤ k ≤ 5
–22 ≤ l ≤ 22
5211
1640
1027
–19 ≤ h ≤ 19
–10 ≤ k ≤ 10
–10 ≤ l ≤ 11
8879
1291
1114
–22 ≤ h ≤ 23
–15 ≤ k ≤ 15
–14 ≤ l ≤ 14
9821
2511
2139
–11 ≤ h ≤ 11
–17 ≤ k ≤ 15
–13 ≤ l ≤ 12
10137
2690
2182
Reflections collected
Reflections unique
Reflections obsd.
Rint
0.0529
0.0336
0.0313
0.0352
Parameters refined
θ range [°]
118
91
168
209
4.20–25.35
0.0499, 0.0961
0.0985, 0.1167
1.056
4.33–25.35
0.0398, 0.1043
0.0466, 0.1098
1.045
4.16–26.37
0.0320, 0.0770
0.0408, 0.0820
1.068
4.11–26.37
0.0335, 0.0753
0.0461, 0.0812
1.038
R1, wR2, [I > 2σ(I)]
R1, wR2 (all data)
GooF
δ
pmax, δpmin/[enm–3
]
0.223, –0.285
0.969, –0.717
0.328, –0.223
0.260, –0.196
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Full Paper
Synthetic Procedures
1 H, H7), 7.39 (dddd, 3JH4H5 = 9.1, 4JH4H6 = 1.6, 4JH2H4 = 1.2, 5JH4H7
=
0.5 Hz, 1 H, H4), 7.23 (dddd, JPH2 = 37.5, JH1H2 = 2.3, JH2H4 = 1.2,
2
4
4
2-Chloro-2,3-dihydro-1H-[1,3]azaphospholo[1,5-a]pyridin-4-
ium Chloride (8): (Chloromethyl)dichlorophosphine (1) (375 mg,
2.5 mmol) was dissolved in THF (25 mL) and cooled to 0 °C. With
stirring PicTMS (6) (413 mg, 2.5 mmol, 1 equiv.) was added dropwise
and the temperature was raised to room temperature overnight.
The resulting suspension was shortly heated to reflux. After reach-
ing ambient temperature again, the reaction mixture was concen-
trated to a total volume of 5 mL. The colorless precipitate was sepa-
rated, washed with THF and dried in vacuo. Compound 8 was ob-
tained as a colorless to yellow solid (293 mg, 1.42 mmol, 57 %). 31P
NMR (162 MHz, CDCl3): δ = 68.7 ppm. 1H NMR (400 MHz, CDCl3):
3
3
5JH2H5 = 0.4 Hz, 1 H, H2), 6.76 (dddd, JH4H5 = 9.1, JH5H6 = 6.5,
4JH5H7 = 1.0, JH2H5 = 0.4 Hz, 1 H, H5), 6.54 (dddd, JH6H7 = 7.0,
5
3
3JH5H6 = 6.5, 4JH4H6 = 1.6, 5JPH6 = 0.7 Hz, 1 H, H6) ppm. 13C{1H} NMR
2
1
(101 MHz, CDCl3): δ = 142.1 (d, JPC = 8.9 Hz, C3), 140.6 (d, JPC
51.5 Hz, C1), 127.5 (C7), 120.1 (d, JPC = 5.4 Hz, C4), 119.4 (d, JPC
=
=
3
4
1
4
1.7 Hz, C5), 118.5 (d, JPC = 45.6 Hz, C2), 111.9 (d, JPC = 2.5 Hz,
C6) ppm. HRMS (DEI): Mcalc: 135.0238. Mfound: 135.0239 (M+, 100 %).
[1,3]Azaphospholo[1,5-a]quinoline (7): (Chloromethyl)dichloro-
phosphine (1) (450 mg, 3 mmol, 1 equiv.) was dissolved in THF
(15 mL). With vigorous stirring QuinTMS (12) (1.292 g, 6 mmol,
2 equiv.) was added dropwise and the solution heated to reflux for
five minutes which caused the formation of a colorless precipitate.
After stirring for 12 h at ambient temperature the precipitate was
removed and the filtrate concentrated in vacuo. After extraction of
the crude product with pentane (25 mL) 7 was obtained as a pale
3
4
5
δ = 9.46 (ddd, JH6H7 = 6.7, JH5H7 = 1.4, JH4H7 = 0.7 Hz, 1 H, H7),
3
3
4
8.37 (ddd, JH4H5 = 8.0, JH5H6 = 7.2, JH5H7 = 1.4 Hz, 1 H, H5), 8.03
3
4
5
(ddd, JH4H5 = 8.0, JH4H6 = 1.1, JH4H7 = 0.7 Hz, 1 H, H4), 7.92 (ddd,
3JH5H6 = 7.2, JH6H7 = 6.7, JH4H6 = 1.1 Hz, 1 H, H6), 5.98 (d, JPH1
=
3
4
2
13.6 Hz, 2 H, H1), 4.48 (d, JPH2 = 11.5 Hz, 2 H, H2) ppm. 13C{1H}
2
yellow solid (311 mg, 1.68 mmol, 56 %). 31P NMR (162 MHz, CDCl3):
4
NMR (101 MHz, CDCl3): δ = 158.4 (C3), 144.8 (d, JPC = 0.7 Hz, C5),
2
δ = 115.7 ppm. 1H NMR (400 MHz, CDCl3): δ = 9.05 (ddd, JPH1
=
3
3
144.2 (d, JPC = 2.5 Hz, C7), 127.4 (d, JPC = 1.5 Hz, C4), 126.1
(C6) ppm. Due to low solubility the signals of carbon atoms 1 and
2 could not be resolved.
4
5
3
37.1, JH1H2 = 2.3, JH1H4 = 0.5 Hz, 1 H, H1), 8.06 (dtd, JH8H9 = 8.5,
4JH8H10
=
5JPH10 = 1.2, JH8H11 = 0.5 Hz, 1 H, H8), 7.67 (dddd,
5
3JH10H11 = 7.8, JH9H11 = 1.6, JH8H11 = 0.5 Hz, 1 H, H11), 7.58 (ddd,
4
5
2-(Pyridin-2-ylmethyl)-2,3-dihydro-1H-[1,3]azaphospholo[1,5-
a]pyridin-4-ium Chloride (9): (Chloromethyl)dichlorophosphine
(1) (150 mg, 1 mmol, 1 equiv.) was dissolved in THF (5 mL). With
vigorous stirring at 0 °C PicTMS (6) (331 mg, 2 mmol, 2 equiv.) was
added dropwise and the reaction mixture was allowed to reach
room temperature overnight. The resulting suspension was heated
to reflux shortly, allowed to reach room temperature and the volu-
minous yellow-orange precipitate was separated by filtration. The
crude product was washed with THF and extracted with CHCl3
(10 mL) to afford compound 9 as a yellow-orange solid (127 mg,
0.48 mmol, 48 %). 31P NMR (162 MHz, CDCl3): δ = –26.9 ppm. 1H
3JH8H9 = 8.5, JH9H10 = 7.2, JH9H11 = 1.6 Hz, 1 H, H9), 7.40 (ddd,
3
4
3JH10H11 = 7.8, JH9H10 = 7.2, JH8H10 = 1.2 Hz, 1 H, H10), 7.34 (dd,
3
3
3JH4H5 = 9.3, JH2H5 = 0.8 Hz, 1 H, H5), 7.33 (dddd, JPH2 = 36.7,
5
2
4JH1H2 = 2.3, 5JH2H5 = 0.8, 4JH2H4 = 0.5 Hz, 1 H, H2), 7.10 (dt, 3JH4H5
=
9.3, JH2H4 = JH1H4 = 0.5 Hz, 1 H, H4) ppm. 13C{1H} NMR (101 MHz,
4
5
CDCl3): δ = 141.0 (d, 2JPC = 8.9 Hz, C3), 140.2 (d, 1JPC = 51.6 Hz, C1),
5
5
128.9 (d, JPC = 0.9 Hz, C11), 128.7 (d, JPC = 0.7 Hz, C9), 127.6 (C7),
6
4
125.0 (d, JPC = 1.1 Hz, C10), 124.0 (d, JPC = 1.4 Hz, C6), 121.8 (d,
3
4
1JPC = 45.1 Hz, C2), 121.2 (d, JPC = 1.7 Hz, C4), 119.7 (d, JPC
=
:
4
4.1 Hz, C5), 115.6 (d, JPC = 0.7 Hz, C8) ppm. HRMS (DEI): Mcalc
185.0394. Mfound: 185.0407 (M+, 100 %). C11H8NP (185.16): calcd. N
7.56, C 71.35, H 4.35; found N 7.39, (–0.17), C 70.61, (–0.74), H 4.60,
(+0.25).
3
NMR (400 MHz, CDCl3): δ = 9.20 (d, JH6H7 = 6.3 Hz, 1 H, H7), 8.12
3
4
3
(dd, JH12H13 = 7.6, JH11H13 = 1.5 Hz, 1 H, H13), 8.10 (ddd, JH4H5
=
3
4
5
8.0, JH4H6 = 7.3, JH5H7 = 1.9, JPH5 = 0.9 Hz, 1 H, H5), 7.75 (d,
3JH4H5 = 8.0 Hz, 1 H, H4), 7.63 (ddt, 3JH5H6 = 7.3, 3JH6H7 = 6.3, 4JH4H6
0.8 Hz, 1 H, H6), 7.49 (td, 3JH10H11 = 3JH11H12 = 7.7, 4JH11H13 = 1.5 Hz,
Procedure for in-Situ NMR Spectroscopy of the Reaction of 1
with PicTMS (6): In a flame-dried 10 mL Schlenk flask, equipped
with a magnetic stirring bar, [D8]THF (0.5 mL) was dried by adding
five sticks of activated 3 Å molecular sieves. (Chloromethyl)dichloro-
phosphine (1) (37.5 mg, 0.25 mmol, 1 equiv.) was added and the
solution cooled to –80 °C. With vigorous stirring PicTMS (6)
(94.9 mg, 0.58 mmol, 2.3 equiv.) was added and the reaction mix-
ture directly transferred into a pre-cooled NMR tube. The sample
was inserted into the NMR spectrometer which was cooled to
–60 °C. At first 31P, 31P{1H} and 1H NMR spectra were recorded to
check the purity of the solution and the stoichiometry. By setting
the temperature to 0 °C the reaction was initiated and the respec-
=
3
3
1 H, H11), 7.39 (d, JH10H11 = 7.7 Hz, 1 H, H10), 6.97 (tt, JH12H13
=
7.7, 4JH10H12 = 1.0 Hz, 1 H, H12), νH1 = 5.66, νH1′ = 5.30 (ABX system,
2JH1H1′ = 15.4, JPH1 = 21.2, JPH1′ = 0.0 Hz, 2 H, H1), νH2 = 3.83,
2
2
2
2
2
νH2′ = 3.75 (ABX system, JH2H2′ = 18.6, JPH2 = 18.6, JPH2′ = 2.0 Hz,
2
2 H, H2), 3.03 (d, JPH8 = 2.8 Hz, 2 H, H8) ppm. 13C{1H} NMR
2
2
(101 MHz, CDCl3): δ = 157.5 (d, JPC = 4.4 Hz, C3), 155.1 (d, JPC
=
3.0 Hz, C9), 146.1 (C13), 144.4 (C5), 143.9 (d, 3JPC = 1.9 Hz, C7), 139.2
3
(C11), 126.4 (C4), 125.3 (C6), 124.8 (d, JPC = 2.6 Hz, C10), 122.1 (d,
5JPC = 1.0 Hz, C12), 59.8 (d, JPC = 32.5 Hz, C1), 32.2 (d, JPC
=
:
1
1
1
22.5 Hz, C2), 31.4 (d, JPC = 24.4 Hz, C8) ppm. HRMS (FAB): Mcalc
1
tive H, 13C{1H}, 31P and 31P{1H} experiment performed in order to
229.0915. Mfound: 229.0917 (M+, 100 %).
identify the intermediates.
2-Phosphaindolizine (5): (Chloromethyl)dichlorophosphine (1)
(750 mg, 5 mmol, 1 equiv.) was dissolved in THF (40 mL). With
vigorous stirring PicTMS (6) (825 mg, 5 mmol, 1 equiv.) was added
dropwise and the mixture heated to reflux for five minutes which
resulted in the formation of a colorless precipitate. Triethylamine
(1.39 mL, 10 mmol, 2 equiv.) was added with stirring to the hot
suspension and the heat source was removed. In the next several
minutes a color change from colorless to orange could be observed.
After stirring for 20 h at room temperature the precipitate was re-
moved and the filtrate concentrated in vacuo to give 14 as an
orange solid contaminated with triethylammonium chloride. 31P
Chloromethyl(picolyl)chlorophosphine (10): 31P NMR (162 MHz,
1
[D8]THF, 0 °C): δ = 91.4 ppm. H NMR (400 MHz, [D8]THF, 0 °C): δ =
8.43 (ddt, 3JH5H6 = 4.9, 4JH4H6 = 1.9, 5JH3H6 = 5JPH6 = 1.0 Hz, 1 H, H6),
3
3
4
5
7.64 (dddd, JH3H4 = 7.8, JH4H5 = 7.5, JH4H6 = 1.9, JPH4 = 0.9 Hz, 1
3
4
5
4
H, H4), 7.25 (dddd, JH3H4 = 7.8, JH3H5 = 1.4, JH3H6 = 1.0, JPH3
=
=
=
0.5 Hz, 1 H, H3), 7.15 (ddt, 3JH4H5 = 7.5, 3JH5H6 = 4.9, 4JH3H5 = 6JPH5
2
2
1.4 Hz, 1 H, H5), 4.16 (d, JPH1 = 11.5 Hz, 2 H, H1), 3.61 (d, JPH8
4.9 Hz, 2 H, H8) ppm. 13C{1H} NMR (101 MHz, [D8]THF, 0 °C): δ =
2
3
156.2 (d, JPC = 6.6 Hz, C2), 149.4 (C6), 136.7 (C4), 124.0 (d, JPC
3.4 Hz, C3), 121.9 (d, JPC = 2.1 Hz, C5), 45.0 (d, JPC = 47.3 Hz, C8),
40.3 (d, JPC = 31.6 Hz, C1) ppm.
=
5
1
1
1
NMR (162 MHz, CDCl3): δ = 120.6 ppm. H NMR (400 MHz, CDCl3):
2
4
4
δ = 8.30 (ddd, JPH1 = 37.9, JH1H2 = 2.3, JH1H7 = 1.0 Hz, 1 H, H1), Chloromethylbis(picolyl)phosphine (11): 31P NMR (162 MHz,
8.02 (dqd, 3JH6H7 = 7.0, 4JH5H7 = 4JH1H7 = 4JPH7 = 1.0, 5JH4H7 = 0.5 Hz,
[D8]THF, 0 °C): δ = –12.6 ppm. 1H NMR (400 MHz, [D8]THF, 0 °C): δ =
Eur. J. Inorg. Chem. 2016, 726–735
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734
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
3
4
5
8.41 (ddd, JH5H6 = 4.9, JH4H6 = 1.9, JH3H6 = 0.9 Hz, 2 H, H6), 7.57
The authors are thankful to Prof. T. M. Klapötke for the generous
allocation of diffractometer time and his continuous support.
3
3
4
5
(dddd, JH3H4 = 7.8, JH4H5 = 7.1, JH4H6 = 1.9, JPH4 = 0.5 Hz, 2 H,
3
4
5
H4), 7.18 (ddd, JH3H4 = 7.8, JH3H5 = 1.1, JH3H6 = 0.9 Hz, 2 H, H3),
7.03 (ddt, 3JH4H5 = 7.1, 3JH5H6 = 4.9, 4JH3H5 = 6JPH5 = 1.1 Hz, 2 H, H5),
3.87 (d, 2JPH8 = 7.3 Hz, 2 H, H8), νH1 = 3.22, νH1′ = 3.11 (ABX system,
Keywords: P heterocycles · N heterocycles · Cyclization ·
Phosphanes
2JH1H1′ = 13.6, JPH1 = 0, JPH1 = 2.0 Hz, 4 H, H1) ppm. 13C{1H} NMR
2
2
2
(101 MHz, [D8]THF, 0 °C): δ = 159.6 (d, JPC = 5.9 Hz, C2), 150.4 (d,
4JPC = 1.0 Hz, C6), 137.0 (C4), 124.4 (d, JPC = 4.2 Hz, C3), 121.9 (d,
3
[1] R. K. Bansal, K. Karaghiosoff, N. Gupta, A. Schmidpeter, C. Spindler, Chem.
Ber. 1991, 124, 475–480.
5JPC = 1.9 Hz, C5), 42.2 (d, 1JPC = 36.3 Hz, C1), 34.6 (d, 1JPC = 18.5 Hz,
[2] U. Bergsträßer, A. Hoffmann, M. Regitz, Tetrahedron Lett. 1992, 33, 1049–
1052.
[3] R. K. Bansal, A. Surana, N. Gupta, Tetrahedron Lett. 1999, 40, 1565–1568.
[4] N. Sogani, P. Maheshwari, R. K. Bansal, Phosphorus Sulfur Silicon Relat.
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1986, 28, 289–296.
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[7] C. Hettstedt, M. Unglert, R. J. Mayer, P. Mayer, A. Frank, K. Karaghiosoff,
2015, manuscript in preparation.
[8] N. Gupta, C. B. Jain, J. Heinicke, N. Bharatiya, R. K. Bansal, P. G. Jones,
Heteroat. Chem. 1998, 9, 333–339.
[9] A. F. Holleman, N. Wiberg, Lehrbuch der anorganischen Chemie, de Gru-
yter & Co., Berlin, 1995.
[10] F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen, R. Taylor,
J. Chem. Soc. Perkin Trans. 2 1987, S1–S19.
[11] a) A. Bondi, J. Phys. Chem. 1964, 68, 441–451; b) M. Mantina, A. C. Cham-
berlin, R. Valero, C. J. Cramer, D. G. Truhlar, J. Phys. Chem. A 2009, 113,
5806–5812.
[12] CrysAlis CCD, version 1.171.27p5 beta (release 01-04-2005 Crys-
Alis171.NET; compiled April 1, 2005, 17:53:34), Oxford Diffraction Ltd.,
Oxfordshire, UK.
[13] CrysAlis RED, version 1.171.27p5 beta (release 01-04-2005 Crys-
Alis171.NET; compiled April 1, 2005, 17:53:34), Oxford Diffraction Ltd.,
Oxfordshire, UK.
[14] Details related to SIR-92, A Program for Crystal Structure Solution, see:
a) A. Altomare, G. L. Cascarano, C. Giacovazzo, A. Guagliardi, J. Appl. Crys-
tallogr. 1993, 26, 343–350; b) A. Altomare, M. C. Burla, M. Camalli, G. L.
Cascarano, C. Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori, R.
Spagna, J. Appl. Crystallogr. 1999, 32, 115–119; c) L. J. Farrugia, J. Appl.
Crystallogr. 2012, 45, 849–854; d) G. M. Sheldrick, SHELXS-97, Program for
Crystal Structure Solution, University of Göttingen, Germany, 1997.
[15] G. M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal Struc-
tures, University of Göttingen, Germany, 1999.
C8) ppm.
Procedure for in-situ NMR Spectroscopy of the Reaction of 1
with QuinTMS (12): A flame-dried 10 mL Schlenk flask, equipped
with a magnetic stirring bar, [D8]THF (0.5 mL) was dried by adding
five sticks of activated 3 Å molecular sieve. Chloromethyl dichloro-
phosphine (1) (37.5 mg, 0.25 mmol, 1 equiv.) was added and the
solution cooled to –100 °C. With vigorous stirring QuinTMS (12)
(134.0 mg, 0.62 mmol, 2.3 equiv.) was added and the solution di-
rectly transferred into a pre-cooled NMR tube. The sample was in-
serted into the NMR spectrometer which was cooled to –70 °C and
at first 31P, 31P{1H} and 1H NMR spectra were recorded to check
the purity of the solution and the stoichiometry. By setting the
temperature to –40 °C the reaction was initiated and the respective
1H, 13C{1H}, 31P and 31P{1H} experiments were performed in order
to identify intermediates.
Chloromethyl(quinaldinyl)chlorophosphine (14): 31P NMR
(162 MHz, [D8]THF, –40 °C): δ = 90.8 (ddt, J = 11.7, 7.5, 3.1 Hz) ppm.
Chloromethylbis(quinaldinyl)phosphine (13): 31P NMR (162 MHz,
[D8]THF, –40 °C): δ = –12.8 (t, J = 7.3 Hz) ppm. H NMR (400 MHz,
1
3
[D8]THF, –40 °C): δ = 8.08 (d, JH8H9 = 8.4 Hz, 1 H, H9), 7.96 (d,
3JH3H4 = 8.6 Hz, 1 H, H4), 7.77 (d, 3JH6H7 = 8.1 Hz, 1 H, H6), 7.62 (ddt,
3JH8H9 = 8.4, 3JH7H8 = 6.9, 4JH6H8 = 1.3 Hz, 1 H, H8), 7.43 (ddt, 3JH6H7
=
3
4
3
8.1, JH7H8 = 6.9, JH7H9 = 1.2 Hz, 1 H, H7), 7.38 (dd, JH3H4 = 8.6,
4JPH3 = 0.6 Hz, 1 H, H3), 4.05 (d, JPH11 = 7.5 Hz, 2 H, H11), νH1
=
=
2
2
2
2
3.48, νH1′ = 3.38 (ABX system, JH1H1′ = 13.6, JPH1 = 0.7, JPH1′
0 Hz, 2 H, H1) ppm. 13C{1H} NMR (101 MHz, [D8]THF, –40 °C): δ =
2
4
159.0 (d, JPC = 6.3 Hz, C2), 148.4 (d, JPC = 0.8 Hz, C10), 136.3 (C4),
129.4 (C8), 129.2 (C9), 129.1 (d, JPC = 2.5 Hz, C5), 126.9 (d, JPC
1.3 Hz, C6), 125.9 (C7), 122.3 (d, JPC = 3.6 Hz, C3), 41.4 (d, JPC
36.7 Hz, C1), 34.3 (d, JPC = 18.4 Hz, C11) ppm.
5
6
=
=
3
1
1
[16] L. A. Spek, PLATON, A Multipurpose Crystallographic Tool, Utrecht Univer-
sity, The Netherlands, 1999.
[17] SCALE3 ABSPACK scaling algorithm, CrysAlis RED, Oxford Diffraction Ltd.,
version 1.171.32.38, Oxford Diffraction Ltd., Oxfordshire, UK.
Acknowledgments
Financial support from the Department of Chemistry, Ludwig-
Maximilian University of Munich is gratefully acknowledged.
Received: September 30, 2015
Published Online: December 15, 2015
Eur. J. Inorg. Chem. 2016, 726–735
www.eurjic.org
735
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim