Mechanism of Photoinduced Reactions between 1-Acetylisatin and Aldehydes

Article abstract of DOI:10.1002/ejoc.200300444

Hydrogen atom abstraction from aliphatic (2a, 2b) and aromatic (2c, 2d, 2e) aldehydes by the triplet nπ* state of 1-acetylisatin (1) yielded triplet (isatin ketyl-aldehyde acyl) radical pairs, which follow an out-of-cage pathway in subsequent reactions to give a series of radical coupling products 4-7. This out-of-cage mechanism is supported by examination of the primary products at various degrees of conversions during the course of the reaction, by the results of addition reactions of thermally generated isatin acyl radical with neutral 1, and by calculation of the charge density distribution in the acyl radicals and in ground state 1. Therefore, the oxygen-philic attack of the acyl radical, which had escaped out of cage from the triplet radical pair, at the C(3) carbonyl oxygen atom of a ground state 1 selectively afforded the thermodynamically more stable addition radical B. The recombination of two radicals B gave the 3-indolinone dimers 4 and 5 as diastereomers, while coupling of B with the isatin ketyl furnished the dihydroisoindigo derivative 6. Isatide 7 was also formed by ketyl radical recombination. The product ratio is dependent on the structure of the aldehyde. For 2d and 2e, each with an electron-donating substituent in the benzene ring, the corresponding acyl radicals are less electrophilic because of a diminished positive charge density at the carbonyl carbon atom, and the formation of the addition radical B is a slow process relative to the encounter and recombination of the isatin ketyl radicals. As a result, products 6d and 6e from cross-coupling of the isatin ketyl and radical B are formed in much lower yields than 6a, 6b, and 6c. The 3-acetyloxy-2-indolinone 3 turned out to be a secondary product derived from the decomposition of 6 during the workup procedures. Since all the primary products are formed by out-of-cage radical pair combination processes, no chain mechanism is involved. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejoc.200300444

FULL PAPER
Mechanism of Photoinduced Reactions between 1-Acetylisatin and Aldehydes
Yan Zhang,[a] Lei Wang,[a] Ye Zhu,[a] and Jian-Hua Xu*[a]
Keywords: Aldehydes / Hydrogen abstraction / Photochemistry / Radical reactions
Hydrogen atom abstraction from aliphatic (2a, 2b) and aro- was also formed by ketyl radical recombination. The product
matic (2c, 2d, 2e) aldehydes by the triplet nπ* state of 1-
acetylisatin (1) yielded triplet (isatin ketyl-aldehyde acyl)
radical pairs, which follow an out-of-cage pathway in sub-
ratio is dependent on the structure of the aldehyde. For 2d
and 2e, each with an electron-donating substituent in the
benzene ring, the corresponding acyl radicals are less elec-
sequent reactions to give a series of radical coupling products trophilic because of a diminished positive charge density at
4−7. This out-of-cage mechanism is supported by examina- the carbonyl carbon atom, and the formation of the addition
tion of the primary products at various degrees of conversions
radical B is a slow process relative to the encounter and re-
during the course of the reaction, by the results of addition combination of the isatin ketyl radicals. As a result, products
reactions of thermally generated isatin acyl radical with
neutral 1, and by calculation of the charge density distribu-
6d and 6e from cross-coupling of the isatin ketyl and radical
B are formed in much lower yields than 6a, 6b, and 6c. The
tion in the acyl radicals and in ground state 1. Therefore, the 3-acetyloxy-2-indolinone 3 turned out to be a secondary
oxygen-philic attack of the acyl radical, which had escaped
out of cage from the triplet radical pair, at the C(3) carbonyl
product derived from the decomposition of 6 during the
workup procedures. Since all the primary products are
oxygen atom of a ground state 1 selectively afforded the formed by out-of-cage radical pair combination processes, no
thermodynamically more stable addition radical B. The re- chain mechanism is involved.
combination of two radicals B gave the 3-indolinone dimers
4 and 5 as diastereomers, while coupling of B with the isatin
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
ketyl furnished the dihydroisoindigo derivative 6. Isatide 7 Germany, 2004)
Introduction
to be clarified from case to case. There are still confusions
and controversies in this respect. In an early study, Waters
suggested an out-of-cage free radical chain mechanism for
the photoaddition between benzaldehyde and phen-
anthrenequinone to give 9-benzoyloxy-10-hydroxyphen-
anthrene.[5] Bruce later put forward a similar out-of-cage
free radical mechanism, based on trapping of the radical
intermediates by styrene and 1,1-diphenylethylene, to ac-
count for the formation of 2-acetylhydroquinone in the
photoreaction between 1,4-benzoquinone and acetalde-
hyde.[6] In addition, in triplet benzophenone-sensitized pho-
toinduced reductive acylation reactions of benzoquinone
(BQ), the acyl moiety formed by hydrogen abstraction from
the aldehyde by the triplet benzophenone obviously adds to
the BQ by an out-of-cage pathway.[2] On the other hand,
from product studies and photo-CIDNP measurements,
Maruyama suggested that photoinduced reactions of o-qui-
nones (phenanthrenequinone[7a,7c] and 1,2-naphtho-
quinone[7d]) and p-quinone (1,4-naphthoquinone[3]) with
aliphatic and aromatic aldehydes predominately follow the
in-cage pathway.
Aldehydes each have a weak C(O)ϪH bond with a dis-
sociation enthalpy of 86Ϯ1[1a] (or 89.3Ϯ0.4[1b,1c]
kcal·molϪ1, similar to that in benzylic (88Ϯ1 kcal·molϪ1 [1a]
and allylic (86Ϯ1 kcal·molϪ1 [1a]
CϪH bonds. As a result,
)
)
)
aldehydes serve as good hydrogen atom donors for nπ* trip-
let excited carbonyl compounds. There have been several
investigations on hydrogen abstraction reactions of triplet
p-quinones[2Ϫ4] and o-quinones[5Ϫ7] from aldehydes from
synthetic and mechanistic viewpoints. These reactions are
of special synthetic value because they provide straightfor-
ward and efficient routes to acetylquinones (the photo-
FriedelϪCrafts reaction) and acetyloxyarenes. Mechan-
istically, two distinct reaction pathways for the triplet se-
miquinone-acyl radical pairs formed in the hydrogen ab-
straction step have been suggested. They could either un-
dergo in-cage radical pair recombination after intersystem
crossing (ISC) to give an adduct, or else the two radicals in
the pair might escape out of cage and take part in sub-
sequent reactions in the bulk solution. Which pathway is
taken may depend on the structures of the quinone and the
aldehyde, as well as on reaction conditions, and may have
1-Acetylisatin (1) has an nπ* triplet state with a triplet
energy of about 64 kcal·mol
.
Ϫ1 [8,9a] We have recently investi-
gated photoinduced [2ϩ2]
cycloadditions
(the
[a]
Department of Chemistry, Nanjing University
Nanjing 210093, China
E-mail: xujh@nju.edu.cn
PaternoϪBüchi reaction) between 1 and a series of al-
kenes[9a,9b] and alkynes.[10] In the photoinduced reaction
Eur. J. Org. Chem. 2004, 527Ϫ534
DOI: 10.1002/ejoc.200300444
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527

Y. Zhang, L. Wang, Y. Zhu, J.-H. Xu
FULL PAPER
between 1 and phenylacetylene,[10] a pair of diastereoiso-
meric 2:1 addition products I is derived from a secondary
reaction by the hydrogen abstraction from the aldehyde
functionality of the primary product II by triplet excited 1.
To gain more insight into the mechanistic details of the trip-
let hydrogen abstraction of o-quinones from aldehydes, we
investigated photoinduced reactions between 1 and both
aliphatic and aromatic aldehydes 2aϪ2e.
at different time intervals during the photolysis indicated
that only products 4, 6 and 7 were the primary products
formed in the photoreactions, while 3 and 9 were absent in
the photolysate throughout the reaction course and were
derived during the subsequent workup procedures. A con-
trol experiment on the thermal reactions of 6c (vide infra)
further showed that 6c is thermally labile when absorbed
on silica gel and gave 3c (58%) and 8 (21%) as the main
decomposition products when heating on silica gel (see Exp.
Sect.). In another control experiment, the pinacol 7 was
also found to be thermally labile, decomposing quantitat-
ively into 8 when heated in the presence of silica gel. The
reaction pathway resulting in the thermal conversion of 6
to 3 and 8 is outlined in Scheme 1. Deprotonation of the
hydroxy group in 6 resulted in its decomposition to isatin 1
Results and Discussion
The longest-wavelength absorption band in the UV spec-
trum of 1-acetylisatin (1),[8] at 347Ϫ379 nm (ε ϭ 2.84 ϫ 103
L·molϪ1·cmϪ1), shows a hypsochromic shift with increasing
solvent polarity and is assigned as an nπ* band. This long-
wavelength absorption tails well into the visible region.
Photoinduced reactions between 1 and compounds 2 were
therefore carried out in dry benzene solution with light of
λ Ͼ 400 nm for selective excitation of 1. The reactions pro-
ceeded rapidly, with gradual fading of the yellow color of
1. In the case of the photoreaction between 1 and 2a, com-
plete conversion of 1 was reached in 4 hr. Chromatographic
separation of the reaction mixture gave the 3-acyloxy-2-in-
dolinone 3a (11%), two 3,3Ј-dihydroisoindigo derivatives Ϫ
3,3Ј-diacyloxy-3,3Ј-bi-2H-indole-2,2Ј-dione 4 (27%) and the
3-acyloxy-3Ј-hydroxy-3,3Ј-bi-2H-indole-2,2Ј-dione 6 (36%),
isatide 7 (5%), and N-acylanthranilic acid (9) (15%). How-
1
Scheme 1
ever, H NMR spectral monitoring of the reaction course
528
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Photoinduced Reactions between 1-Acetylisatin and Aldehydes
FULL PAPER
Table 1. Photoinduced reactions between 1 and 2
2
Irradiation time (h)
Conversion (%)[a]
Products and yield (%)[b]
2a
2b
2c
2d
2e
4
1.5
3
3
9
100
100
100
100
100
3a (11), 4a (27), 6a (36), 7 (5), 9 (15)
3b (15), 4b (11), 5b (14), 6b (30), 7 (16), 9 (12)
3c (9), 4c (11), 5c (17), 6c (34), 7 (19), 8(6)
3d (15), 4d (17), 5d (24), 7 (22), 8 (14), 9 (3)
3e (33), 4e (25), 7 (21)
[a] All the reactions were carried out in benzene solution under nitrogen. [1] ϭ 0.05 mol·LϪ1, [RCHO] ϭ 0.5 mol·LϪ1 [b] Yield of isolated
.
pure product.
and 3-acyloxy-3-oxindolyl anion, which on protonation ing (ISC) followed by radical pair recombination should
gave 3. Meanwhile, a separate experiment showed that the have resulted in the formation of the adducts 10 and/or 11.
isatin adsorbed on silica gel containing trace amounts of The absence of these products clearly indicates that no in-
water is hydrolyzed into 8 upon heating (Scheme 1).
cage mechanism is involved in the reactions between 1 and
Photoinduced reactions between 1 and 2bϪ2e in benzene 2aϪ2e. At the same time, the structures of the primary
solution were also investigated, and these gave results simi- products 4Ϫ7 show that they are all formed in out-of-cage
lar to the reaction between 1 and 2a, with the correspond- reactions by radical pair combination in the bulk solution.
ing compounds 4, 5, 6, and 7 as the primary products di- The initially formed isatin ketyl-aldehyde acyl radical pair
rectly formed in the photoreaction. During the workup pro- A (Scheme 2) is of triplet multiplicity, and escape out of
cedures, various quantities of 3, 8, and 9 were obtained cage is favored for these long-lived triplet radical pairs.[12]
(Table 1). The structures of compounds 3Ϫ7 were mainly As electrophilic radicals, the acyl moieties have shown spe-
determined by spectral (1H NMR, IR, MS) and elemental cial ‘‘oxygen-philic’ reactivity in several reactions with alde-
analysis data. However, since it is difficult to establish un- hydes and ketones,[13] being apt to attack the carbonyl at
ambiguously merely from the spectral data whether the acyl the oxygen atom, resulting in homolytic cleavage of the Cϭ
moiety in the primary products 4Ϫ6 is linked to the C(2) or O bond, giving radical B (Scheme 2). This oxygen-philic re-
C(3) carbonyl oxygen atom of 1, an X-ray crystallographic activity of the acyl group toward the carbonyl oxygen atom
analysis of 6a was undertaken, and showed that the acyl is in 1 can be best interpreted by inspection of the charge
linked to the C(3)-carbonyl oxygen atom of 1 (Figure 1). density distribution in the acyl radicals and in ground state
Figure 1 also showed that 6a is a dl isomer with the two 1, as shown in Figure 2. The atomic charges were calculated
chiral atoms having (R,R) configuration. The structure of by the DFT method at the UB3LYP/6Ϫ31G* level for the
4d (the dl-diastereomer) was also established by X-ray crys- acyl radicals derived from 1aϪ1e and at the B3LYP/
tallographic analysis.[11]
6Ϫ31G* level for 1. The two carbonyl oxygen atoms in 1
Unlike in phenanthrenequinone, the non-equivalence of are both seen to be heavily negatively charged, while the
the two carbonyl groups in 1 allows unequivocal differen- acyl radicals are positively charged at the carbonyl carbon
tiation between the in-cage and out-of-cage products from atom. However, although the two carbonyl oxygen atoms
their structures. In these reactions we have not found any in 1 have similar negative charge densities, electrophilic at-
products that may be derived from an in-cage process. Had tack by the acyl radical takes place exclusively at the C(3)
any in-cage mechanism played any role, intersystem cross- carbonyl oxygen in 1. The reason for this profound selec-
tivity in the reaction site can be looked for in the different
thermodynamic stabilities of the two addition radicals B
and C (Scheme 2). Semiempirical AM1 calculation of the
formation enthalpy (∆Hf) indicated that radicals B and C
derived from 2c have ∆Hf values of Ϫ53.022 and Ϫ49.233
kcal·molϪ1, respectively, and that B is 3.789 kcal·molϪ1
more stable than C. This means a higher activation en-
thalpy for the addition of acyl at the C(2) carbonyl oxygen
atom. The acyl attack on 1 is therefore directed at the C(3)
carbonyl oxygen atom in 1.
An alternative pathway resulting in the addition radical
B would be through initial single-electron transfer (SET)
from the acyl radical to the ground state 1 to give isatin
ketyl anion radical and acylium cation, followed by ion rad-
ical pair recombination, as first suggested by Bruce as a
mechanistic possibility to account for the o-acylation prod-
uct in the photoreactions of benzoquinone with acetalde-
Figure 1. X-ray structure of 6a
Eur. J. Org. Chem. 2004, 527Ϫ534
hyde.[6b] This concept is a product of early studies on acyl
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Y. Zhang, L. Wang, Y. Zhu, J.-H. Xu
FULL PAPER
Scheme 2
radical additions to aldehydes and ketones at the carbonyl
oxygen,[13] in which the contribution of a polar transition
state is postulated. SET from aliphatic acyl radical to high-
[16]
valent metal cations such as CuII,[14] MnIII [15]
,
FeIII
,
PbIV,[17] etc. has long been established. We calculated the
vertical and adiabetic ionization potentials of the acyl rad-
icals at the UB3LYP/6Ϫ31G* level, and the results are
given in Table 2. For comparison, the adiabetic IPs of for-
myl and acetyl radicals were also calculated, and their cal-
culated IPs are in good agreement with the experimentally
measured values (8.2[18] and 7 eV,[19] respectively). Although
the aliphatic and aromatic acyl radicals have similar IPs, it
is noted that SETs from aromatic acyl radicals to these me-
tal cations are unknown at present. These metal cations are
also much stronger electron acceptors than neutral organic
electron acceptors. As an example, the half-wave reduction
potential of the CuII/CuI couple is in the 0.4Ϫ0.8 V range
(SCE, MeCN),[20] while most neutral organic molecules
red
have negative E values.[21] As a result, SET from acyl rad-
1/2
icals to neutral organic electron acceptors has seldom been
reported. Russell suggested that acyl radicals may be oxid-
ized to acylium cations in DMSO by SET to tert-butylmer-
red
cury chloride,[22] which has an E
more positive than
1/2
Ϫ0.6V (SCE).[23] The E of 1 is Ϫ0.75V (SCE, MeCN).[9a]
red
1/2
Unfortunately, the half-wave oxidation potentials of the
acyl radicals are unknown, and estimation of the enthalpy
for SET between the acyl radicals and ground state 1 by
Figure 2. Atomic charges in: (a) ground state 1, (b) valeroyl radical,
(c) crotonyl radical, (d) p-chlorobenzoyl radical, (e) p-methoxyben-
zoyl radical, and (f) o-hydroxybenzoyl radical (charge density at the
hydrogen atoms has been summed up to their attached carbon
atom)
the Weller equation[24] is not possible. Although the more
red
negative E value of 1 in relation to tBuHgCl and the non-
1/2
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Photoinduced Reactions between 1-Acetylisatin and Aldehydes
FULL PAPER
polarity of the solvent (PhH) used in the photoreactions product in the photoreactions, being formed by thermal de-
between 1 and 2aϪ2e would not favor the SET process and composition of product 6 during the workup procedures.
the formation of the (acylium cation Ϫ ketyl anion) ion This fact also excludes a chain mechanism.
pair, the SET involvement could not be definitely excluded,
To give more insight into the mechanism of the formation
especially in the photoreactions between 1 and the aliphatic of 3Ϫ7 in photoreactions between 1 and 2, we investigated
aldehydes 2a and 2b.
reactions between 1 and 2c induced by thermal decompo-
sition of benzoyl peroxide (BP). Heating of a benzene solu-
tion of BP (20.4 mmol), 1 (7.2 mmol), and 2c (26.8 mmol)
at reflux for 48 h resulted in total consumption of 1 and
gave, after chromatographic separation of the reaction mix-
ture, in addition to biphenyl and benzoic acid derived from
BP, 3c (0.69 mmol, 10%), 4c (0.41 mmol, 12%), 5c
(0.21 mmol, 6%), 6c (1.80 mmol, 50%), 8 (0.31 mmol, 4%),
and 9 (0.18 mmol, 3%). In this case, the p-chlorobenzoyl
radical is generated by hydrogen abstraction from the alde-
hyde 2c by the benzoyloxy radical formed in the decompo-
sition of BP. A geminate isatin ketyl-acyl radical pair (as A
in Scheme 2) is bypassed, and an out-of-cage mechanism
Table 2. Ionization potentials of the acyl radicals derived from
2aϪ2e[a]
Formyl
Acetyl
2a
2b
2c
2d
2e
Vertical IP
(eV)
7.90 8.11 7.93 7.44 7.43
Adiabatic IP 8.29(8.2)[b] 6.97(7.1)[c] 6.40 6.51 6.36 5.82 5.91
(eV)
[a] Calculated at the UB3LYP/6Ϫ31G* level. [b] Experimental value,
ref.[18] [c] Experimental value, ref.[19]
Encounter and combination of two isatin ketyls furnish for the formation of the products is imposed, the p-chlorob-
the isatide 7. Products 4 and 5 are diastereomers, formed enzoyl radical attacking a ground state 1 to furnish radical
by encounter and recombination of the addition radicals B B. The formation of the same products (3Ϫ7) in the BP-
in solution. Product 6, on the other hand, is derived from induced reactions as in the photoreactions between 1 and
encounter and recombination of the addition radical B with 2c lent further support to the photoreaction mechanism as
isatin ketyl, having escaped out of cage following the initial outlined in Scheme 2.
hydrogen abstraction of 31* from the aldehyde. It is notable
that, in the reactions between 1 and 2d or 2e, each of which
Conclusion
has an electron-donating substituent in the benzene ring,
the cross-coupling products (6d and 6e) are absent. Al-
though the presence of 3d and 3e indicates the formation
of 6d and 6e during the photoreaction, their yields are sig-
nificantly lower than those of the corresponding 6aϪ6c.
This phenomenon can be interpreted by the acyl radicals
of 2d and 2e, with the presence of the electron-releasing
substituents, being less electrophilic than the acyls from
2aϪ2c, and therefore more reluctant to add to the carbonyl
oxygen in 1. As a result, after the dissociation of the isatin
ketyl-aldehyde acyl radical pairs and diffusion of the two
types of radicals into the solution, the formation of the ad-
dition radical B would be a rather slow process in relation
to the encounter and recombination of the ketyl radicals
resulting in the isatide 7, and the formation of 6d and 6e
would occur only in the later stage of the whole reaction
sequence when most of the ketyl radicals had been con-
sumed in self-coupling to give 7, the yields of 6d and 6e
therefore being decreased. This argument is supported by
the calculated charge density distribution in the acyl rad-
icals derived from 2d and 2e. Indeed, the carbonyl carbon
atom in these two acyl radicals is less positively charged
than in the acyl radicals derived from 2aϪ2c. Since all the
primary products 4Ϫ7 are derived from radical pair recom-
bination processes, which eliminate free radicals from the
solution, no chain mechanism could be involved in the pho-
toreactions between 1 and 2aϪ2e. Although radical B may
serve as a potential chain carrier by abstracting a hydrogen
atom from the aldehyde 2 to give 3 and an acyl radical
to initiate a new chain, careful examination of the high-
resolution 1H NMR spectra of the reaction mixture at vari-
In summary, photoinduced reactions between 1-acetylisa-
tin (1) and the aldehydes 2aϪ2e give the 3,3Ј-bi-2H-indole-
2,2Ј-dione derivatives 4Ϫ7 as primary products in high total
yield. These reactions follow an out-of-cage mechanism
3
after initial hydrogen abstraction from the aldehyde by 1*
, with the isatin ketyl radicals and the 3-acyloxy-2-oxo-3-
indolinyl radical B formed by an oxygen-philic attack of the
escaped acyl at the C(3) carbonyl of a ground state 1 as the
intervening radical species. All the primary products 4Ϫ7
are formed by self- and cross-coupling reactions of these
two radical species, with the product ratio depending on the
relative rates of the formation of the addition radical B and
the radical coupling reactions.
Experimental Section
1
General Remarks: Melting points are uncorrected. H NMR spec-
tra were recorded with a Bruker DPX 300 at 300 MHz in CDCl3
as solvent. Chemical shifts are reported in δ (ppm). J values are
given in Hz. Infrared spectra were taken with a Shimadzu IR 440
spectrometer in KBr pellets. Mass spectra were recorded with a VG
ZAB-HS spectrometer. Elemental analyses were performed with a
PerkinϪElmer-240C analyzer. Benzene (AR grade) was dried with
sodium and distilled before use. 1-Acetylisatin was recrystallized
from benzene. The aldehydes 2aϪ2e were distilled under reduced
pressure or recrystallized before use.
Calculation Method: The geometry optimization and total energies
of the acyl radicals were calculated by UB3LYP/6Ϫ31G*. In calcu-
lation of the vertical IP, the acyl radical geometry was used for the
ous conversions indicated that product 3 is not a primary acylium cations and the total energy was calculated by B3LYP/
Eur. J. Org. Chem. 2004, 527Ϫ534
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Y. Zhang, L. Wang, Y. Zhu, J.-H. Xu
6Ϫ31G*. In calculation of the adiabetic IPs, the geometry of the 1280, 1160, 1100, 1020, 760 cmϪ1 1H NMR (CDCl3, 300 MHz):
FULL PAPER
.
cation was optimized by B3LYP/6Ϫ31G*. The formation enthalp-
ies of the radicals B and C were calculated by the AM1 method
(Gaussian 98)[25]
δ ϭ 0.93 (t, J ϭ 7.3 Hz, 3 H), 1.38 (m, 2 H), 1.67 (m, 2 H), 2.47
(t, J ϭ 7.5 Hz, 2 H), 2.68 (s, 3 H), 6.03 (s, 1 H), 7.22 (td, J ϭ 7.5,
0.9 Hz, 1 H), 7.36 (d, J ϭ 7.5 Hz, 1 H), 7.37Ϫ7.43 (m, 2 H), 8.25
(d, J ϭ 8.2 Hz, 1 H) ppm. MS: m/z (%) ϭ 275 [Mϩ] (7), 233 (10),
191 (80), 149 (100), 132 (62), 104 (23), 93 (12), 57 (65), 43 (54).
C15H17NO4 (275.3): calcd. C 65.45, H 6.18, N 5.09; found C 65.79,
H 6.36, N 4.85.
Preparative Photolyses: The light source was a medium-pressure
mercury lamp (500 W) in a cooling water jacket, which was further
surrounded by a layer of solution filter (20% aqueous sodium ni-
trite, 1 cm thick) to cut off light of wavelengths shorter than
400 nm. The solution of 1-acetylisatin (1) and an excess amount of
aldehyde in benzene was purged with dry nitrogen for 20 min and
then irradiated with continuous nitrogen purging. At the end of the
reaction, the solution had turned from yellow to colorless. The sol-
vent was removed in vacuo and the residue was separated by flash
chromatography on a silica gel column with petroleum ether (b.p.
60Ϫ90 °C)/ethyl acetate as eluent.
(3R,3ЈR)-1,1Ј-Diacetyl-1,1Ј,3,3Ј-tetrahydro-3,3Ј-dipentanoyl-3,3Ј-bi-
2H-indole-2,2Ј-dione (4b): Colorless oil. IR (KBr): ν˜ ϭ 2900, 1780,
1750, 1720, 1600, 1460, 1330, 1270, 1170, 1000, 770 cmϪ1 1H
.
NMR (CDCl3, 300 MHz): δ ϭ 0.94 (t, J ϭ 7.3 Hz, 6 H), 1.31Ϫ1.43
(m, 4 H), 1.59- 1.70 (m, 4 H), 2.40Ϫ2.60 (m, 10 H), 6.75 (br., 1 H),
7.08 (t, J ϭ 7.5 Hz, 2 H), 7.41 (td, J ϭ 8.0, 1.4 Hz, 2 H), 8.16 (d,
J ϭ 8.1 Hz, 2 H) ppm. MS: m/z (%) ϭ 359 (6), 321 (3), 275 (45),
191 (77), 149 (23), 85 (100). C30H32N2O8 (548.6): calcd. C 65.69,
H 5.84, N 5.11; found C 65.87, H 6.05, N 4.87.
Photolysis of 1 with Crotonaldehyde 2a: A solution of 1 (570 mg,
3 mmol) and 2a (1.05 g, 15 mmol) in benzene (60 mL) was photo-
lyzed for 4 h to reach complete conversion of 1. Workup as de-
scribed above gave 3a (85 mg, 11%), 4a (210 mg, 27%), 6a (240 mg,
36%), 7 (30 mg, 5%), and 9 (85 mg, 16%).
(3R,3ЈS)-1,1Ј-Diacetyl-1,1Ј,3,3Ј-tetrahydro-3,3Ј-dipentanoyl-3,3Ј-bi-
2H-indole-2,2Ј-dione (5b): Colorless oil. IR (KBr): ν˜ ϭ 2900, 1780,
1760, 1720, 1600, 1460, 1370, 1330, 1270, 1170, 1080, 1010, 910,
1
760 cmϪ1. H NMR (CDCl3, 300 MHz): δ ϭ 0.92 (t, J ϭ 7.5 Hz,
1-Acetyl-3-(2-butenoyl)-1,3-dihydro-2H-indol-2-one (3a): White
powder (from petroleum ether and ethyl acetate), m.p. 92Ϫ93 °C.
IR (KBr): ν˜ ϭ 2890, 1780, 1710, 1650, 1600, 1450, 1360, 1340,
6 H), 1.23Ϫ1.44 (m, 4 H), 1.55Ϫ1.65 (m, 4 H), 2.46 (t, J ϭ 7.5 Hz,
4 H), 2.61 (s, 6 H), 7.20 (t, J ϭ 7.5 Hz, 2 H), 7.29Ϫ7.42 (m, 6 H),
8.11 (d, J ϭ 8.2 Hz, 2 H) ppm. MS: m/z (%) ϭ 275 (7), 256 (7),
233 (10), 191 (12), 149 (44), 129 (69), 105 (7), 97 (12), 85 (40), 43
(100). C30H32N2O8 (548.6): calcd. C 65.69, H 5.84, N 5.11; found
C 65.90, H 5.90, N 4.92.
1260, 1150, 1090, 1020, 950, 750 cmϪ1 1H NMR (CDCl3,
.
300 MHz): δ ϭ 1.94 (dd, J ϭ 6.9, 1.7 Hz, 3 H), 2.71 (s, 3 H), 5.97
(dd, J ϭ 12.1, 1.7 Hz, 1 H), 6.10 (s, 1 H), 6.92Ϫ7.29 (m, 2 H),
7.38Ϫ7.62 (m, 2 H), 8.27 (d, J ϭ 8.2 Hz, 1 H). MS: m/z (%) ϭ 259
[Mϩ] (14), 217 (8), 191 (14), 149 (23), 132 (17), 69 (100).
C14H13NO4 (259.3): calcd. C 64.86, H 5.02, N 5.34; found C 64.85,
H 5.21, N 5.34.
(3R,3ЈR)-1,1Ј-Diacetyl-1,1Ј,3,3Ј-tetrahydro-3Ј-hydroxy-3-pentanoyl-
3,3Ј-bi-2H-indole-2,2Ј-dione (6b): Colorless oil. IR (KBr): ν˜ ϭ 3400,
2900, 1780, 1760, 1720, 1600, 1460, 1370, 1330, 1270, 1160, 1090,
1
1040, 940, 910, 870, 760, 600 cmϪ1. H NMR (CDCl3, 300 MHz):
(3R,3ЈR)-1,1Ј-Diacetyl-1,1Ј,3,3Ј-tetrahydro-3,3Ј-dibutenoyl-3,3Ј-bi-
2H-indole-2,2Ј-dione (4a): Colorless blocks (from petroleum ether
and ethyl acetate), m.p. 190Ϫ192 °C. IR (KBr): ν˜ ϭ 1780, 1720,
1650, 1600, 1450, 1380, 1340, 1280, 1170, 1100, 1000, 760, 600
cmϪ1. 1H NMR (CDCl3, 300 MHz): δ ϭ 1.94 (dd, J ϭ 6.9, 1.7 Hz,
6 H), 2.48 (s, 6 H), 6.03 (dd, J ϭ 15.6, 1.7 Hz, 2 H), 6.80 (br., 1
H), 7.06Ϫ7.45 (m, 8 H), 8.17 (d, J ϭ 8.2 Hz, 2 H). MS: m/z (%) ϭ
516 [Mϩ] (0.4), 327 (14), 259 (8), 146 (5), 69 (100). C28H24N2O8
(516.5): calcd. C 65.12, H 4.65, N 5.43; found C 65.26, H 4.71,
N 5.21.
δ ϭ 0.93 (t, J ϭ 7.5 Hz, 3 H), 1.29Ϫ1.41 (m, 2 H), 1.60Ϫ1.70 (m,
2 H), 2.32 (s, 3 H), 2.41Ϫ2.65 (m, 3 H), 2.69 (s, 3 H), 6.96 (t, J ϭ
7.5 Hz, 1 H), 7.24Ϫ7.53 (m, 5 H), 8.13 (d, J ϭ 8.0 Hz, 1 H), 8.20
(d, J ϭ 7.2 Hz, 1 H) ppm. MS: m/z (%) ϭ 275 (6), 233 (9), 191
(80), 149 (100), 132 (53), 119 (14), 104 (18), 93 (11), 90 (39), 57
(58), 43 (85). C25H24N2O7 (464.5): calcd. C 64.66, H 5.17, N 6.03;
found C 64.72, H 5.52, N 6.11.
Photolysis of 1 with 4-Chlorobenzaldehyde 2c: A solution of 1
(750 mg, 4 mmol) and 2c (562 mg, 4 mmol) in benzene (80 mL) was
photolyzed for 3 h to reach a complete conversion of 1. The solvent
was removed in vacuo and the residue was dissolved in acetone/
petroleum ether. Most of the unstable 6c (352 mg, 34%) crystallized
and the mixture remaining in solution was further separated by
flash chromatography as described above to give 3c (112 mg, 9%),
4c (139 mg, 11%), 5c (225 mg, 17%), and 7 (146 mg, 19%).
(3R,3ЈR)-1,1Ј-Diacetyl-1,1Ј,3,3Ј-tetrahydro-3-(2-butenoyl)-3Ј-
hydroxy-3,3Ј-bi-2H-indole-2,2Ј-dione (6a): Colorless prisms (from
petroleum ether and ethyl acetate) m.p. 130Ϫ131 °C. IR (KBr): ν˜ ϭ
3500, 1760, 1720, 1690, 1650, 1600, 1460, 1380, 1300, 1260, 1160,
1040, 1020, 960, 900, 750, 630 cmϪ1. 1H NMR (CDCl3, 300 MHz):
δ ϭ 1.97 (dd, J ϭ 6.9, 1.7 Hz, 3 H), 2.32 (s, 3 H), 2.69 (s, 3 H),
6.03 (dd, J ϭ 15.6, 1.7 Hz, 1 H), 6.33 (br., 1 H), 6.95 (t, J ϭ 7.4 Hz,
1 H), 7.10 (qd, J ϭ 15.6, 6.9 Hz, 1 H), 7.30Ϫ7.40 (m, 3 H), 7.49
(t, J ϭ 7.8 Hz, 3 H), 8.13 (d, J ϭ 8.1 Hz, 1 H), 8.20 (d, J ϭ 8.2 Hz,
1 H) ppm. MS: m/z (%) ϭ 259 (10), 217 (9), 191 (14), 149 (22), 146
(55), 132 (9), 90 (18), 69 (100). C24H20N2O7 (448.4): calcd. C 64.29,
H 4.46, N 6.25; found C 64.48, H 4.61, N 6.36.
1-Acetyl-3-(p-chlorobenzoyl)-1,3-dihydro-2H-indol-2-one (3c): White
powders (from acetone and petroleum ether), m.p. 146Ϫ148 °C. IR
(KBr): ν˜ ϭ 1778, 1719, 1592, 1467, 1371, 1328, 1261, 1169, 1117,
1
1106, 1014, 758 cmϪ1. H NMR (CDCl3, 300 MHz): δ ϭ 2.73 (s,
3 H), 6.28 (s, 1 H), 7.24 (d, J ϭ 7.4 Hz, 1 H), 7.42Ϫ7.47 (m, 4 H),
8.01Ϫ8.05 (m, 2 H), 8.31 (d, J ϭ 8.0 Hz, 1 H) ppm. 13C NMR
(CDCl3, 75 MHz): δ ϭ 172.92, 170.79, 165.16, 141.34, 140.87,
131.89, 131.21, 129.37, 127.41, 126.04, 125.30, 123.69, 117.37,
77.83, 77.40, 76.98, 70.98, 26.92 ppm. MS: m/z (%) ϭ 329 [Mϩ] (6),
287 (8), 149 (19), 139 (100), 111 (16), 77 (9), 43 (33). C17H12 ClNO4
(329.7): calcd. C 61.91, H 3.64, N 4.25; found C 61.82, H 3.46,
N 4.51.
Photolysis of 1 with Valeraldehyde 2b: A solution of 1 (700 mg,
3.7 mmol) and 2b (0.8 mL, 8 mmol) in benzene (80 mL) was photo-
lyzed for 1.5 h to reach a complete conversion of 1. Workup as
described above gave 3b (150 mg, 15%), 4b (110 mg, 11%), 5b
(140 mg, 14%), 6b (260 mg, 30%), 7 (110 mg, 16%), and 9 (80 mg,
12%).
1-Acetyl-1,3-dihydro-3-pentanoyl-2H-indol-2-one (3b): Colorless oil. (3R,3ЈR)-1,1Ј-Diacetyl-3,3Ј-bis(p-chlorobenzoyl)-1,1Ј,3,3Ј-tetra-
IR (KBr): ν˜ ϭ 2900, 1780, 1760, 1720, 1600, 1460, 1380, 1340, hydro-3,3Ј-bi-2H-indole-2,2Ј-dione (4c): Colorless crystals (from
532
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2004, 527Ϫ534

Photoinduced Reactions between 1-Acetylisatin and Aldehydes
FULL PAPER
acetone and petroleum ether), m.p. 262Ϫ264 °C. IR (KBr): ν˜ ϭ
petroleum ether and ethyl acetate), m.p. 133Ϫ135 °C. IR (KBr):
1775, 1728, 1595, 1488, 1464, 1370, 1335, 1269, 1172, 1117, 1091, ν˜ ϭ 1760, 1720, 1600, 1500, 1460, 1380, 1330, 1260, 1170, 1100,
1
1
1014, 847, 762, 754, 682 cmϪ1. H NMR (CDCl3, 300 MHz): δ ϭ 1020, 940, 850, 760, 700, 600 cmϪ1. H NMR (CDCl3, 300 MHz):
2.51 (s, 6 H), 6.89 (s, 2 H), 7.11 (t, J ϭ 7.5 Hz, 2 H), 7.45Ϫ7.52 δ ϭ 2.79 (s, 6 H), 3.88 (s, 6 H), 6.96 (d, J ϭ 8.5 Hz, 4 H), 7.10 (t,
(m, 6 H), 8.10 (d, J ϭ 8.4 Hz, 4 H), 8.24 (d, J ϭ 8.2 Hz, 2 H) ppm. J ϭ 7.4 Hz, 2 H), 7.22 (d, J ϭ 7.3 Hz, 2 H), 7.34 (t, J ϭ 7.7 Hz, 2
13C NMR (CDCl3, 75 MHz): δ ϭ 170.35, 170.21, 164.00, 141.72,
H), 8.08 (d, J ϭ 8.4 Hz, 6 H) ppm. MS: m/z (%) ϭ 459 (0.4), 304
141.27, 132.43, 131.88, 129.69, 127.24, 125.70, 124.48, 121.21, (3), 262 (9), 220 (6), 152 (11), 146 (10), 135 (100), 107 (14), 92 (9).
117.17, 81.61, 77.85, 77.43, 77.01, 26.49 ppm. MS: m/z (%) ϭ 467 C36H28N2O10 (648.6): calcd. C 66.67, H 4.32, N 4.32; found C
(4), 262 (5), 156 (7), 149 (6), 139 (100), 111 (15), 90 (4), 75 (12), 43
(24). C34H22Cl2N2O8 (657.5): calcd. C 62.10, H 3.35, N 4.26; found
C 62.23, H 3.21, N 4.27.
66.71, H 4.57, N 4.61.
Photolysis of 1 with Salicylaldehyde 2e: A solution of 1 (380 mg,
2 mmol) and 2e (0.4 mL, 4 mmol) in benzene (40 mL) was photo-
lyzed for 9 h to reach complete conversion of 1. Workup as de-
scribed above gave the products 3e (205 mg, 33%), 4e (155 mg,
25%), and 7 (80 mg, 21%).
(3R,3ЈS)-1,1Ј-Diacetyl-3,3Ј-bis(p-chlorobenzoyl)-1,1Ј,3,3Ј-tetra-
hydro-3,3Ј-bi-2H-indole-2,2Ј-dione (5c): Colorless crystals (from
acetone and petroleum ether), m.p. 244Ϫ246 °C. IR (KBr): ν˜ ϭ
1774, 1730, 1594, 1466, 1370, 1333, 1275, 1068, 1016, 941, 852, 756,
686 cmϪ1. 1H NMR (CDCl3, 300 MHz): δ ϭ 2.80 (s, 6 H), 7.09 (t,
J ϭ 7.5 Hz, 2 H),8.08 (m, 4 H), 7.19 (dd, J ϭ 7.5, 1.0 Hz,2 H),
7.31 (td, J ϭ 8.4, 1.0 Hz, 2 H), 7.44Ϫ7.47 (m, 4 H), 8.03 (d, J ϭ
8.3 Hz, 2 H) ppm. MS: m/z (%) ϭ 469 (3), 262 (4), 234 (3), 149 (6),
139 (100), 111 (15), 104 (6), 75 (12), 50 (9). C34H22Cl2N2O8 (657.5):
calcd. C 62.10, H 3.35, N 4.26; found C 62.05, H 3.42, N 4.27.
1-Acetyl-1,3-dihydro-3-(o-hydroxybenzoyl)-2H-indol-2-one
(3e):
Colorless needles (from acetone and petroleum ether), m.p.
153Ϫ154 °C. IR (KBr): ν˜ ϭ 3200, 1760, 1720, 1680, 1600, 1580,
1470, 1450, 1360, 1330, 1270, 1240, 1160, 1140, 1120, 1070, 1000,
760, 690, 650, 580 cmϪ1. H NMR (CDCl3, 300 MHz): δ ϭ 2.75
1
(s, 3 H), 6.32 (s, 1 H), 6.93 (t, J ϭ 7.8 Hz, 1 H), 7.03 (d, J ϭ 8.4 Hz,
1 H), 7.24Ϫ7.29 (m, 1 H), 7. 45Ϫ7.56 (m, 3 H), 7.93 (dd, J ϭ 8.0,
1.7 Hz, 1 H), 8.32 (d, J ϭ 8.3 Hz, 1 H), 10.27 (s, 1 H) ppm. MS:
m/z (%) ϭ 311 (2), 269 (1), 251 (2), 174 (21), 132 (100), 121 (38),
104 (7), 93 (5), 77 (7), 65 (7), 43 (17). C17H13NO5 (311.3): calcd. C
65.59, H 4.18, N 4.50; found C 65.66, H 4.13, N 4.63.
(3R,3ЈR)-1,1Ј-Diacetyl-3-(p-chlorobenzoyl)-1,1Ј,3,3Ј-tetrahydro-3Ј-
hydroxy-3,3Ј-bi-2H-indole-2,2Ј-dione (6c): Colorless crystals (from
acetone and petroleum ether), m.p. 136Ϫ138 °C. IR (KBr): ν˜ ϭ
3409, 1760, 1717, 1595, 1464, 1402, 1269, 1169, 1092, 1014, 756
1
cmϪ1. H NMR (CDCl3, 300 MHz): δ ϭ 2.78 (s, 3 H), 2.81 (s, 3
(3R,3ЈR)-1,1Ј-Diacetyl-1,1Ј,3,3Ј-tetrahydro-3,3Ј-bis(o-hydroxy-
benzoyl)-3,3Ј-bi-2H-indole-2,2Ј-dione (4e): Colorless crystals (from
acetone and petroleum ether), m.p. 203Ϫ204 °C. IR (KBr): ν˜ ϭ
3300, 1760, 1720, 1680, 1600, 1570, 1470, 1360, 1320, 1260, 1150,
H), 7.06 (t, J ϭ 7.5 Hz, 1 H), 7.14 (t, J ϭ 7.5 Hz, 2 H), 7.24Ϫ7.34
(m, 2 H), 7.49 (d, J ϭ 8.7 Hz, 2 H), 7.92Ϫ8.06 (m, 3 H), 8.13 (d,
J ϭ 8.7 Hz, 2 H) ppm. MS: m/z (%) ϭ 329 (1), 287 (2), 189 (2),
161 (2), 146 (33), 141(8), 139 (16), 119 (10), 104 (10), 90 (59), 77
(13), 64 (21), 43 (100). C27H19ClN2O7 (518.9): calcd. C 62.49, H
3.67, N 5.40; found C 62.4, H 3.67, N 5.37.
1120, 1080, 930, 900, 860, 750, 690, 650, 580 cmϪ1 1H NMR
.
(CDCl3, 300 MHz): δ ϭ 2.82 (s, 6 H), 6.96Ϫ7.01 (m, 4 H), 7.13 (t,
J ϭ 7.5 Hz, 2 H), 7.25 (d, J ϭ 7.5 Hz, 2 H), 7.35 (td, J ϭ 7.8,
1.4 Hz, 2 H), 7.54 (td, J ϭ 7.9, 1.8 Hz, 2 H), 8.05 (d, J ϭ 8.2 Hz,
2 H), 8.18 (dd, J ϭ 8.2, 1.6 Hz, 2 H), 9.66 (s, 2 H) ppm. MS: m/z
(%) ϭ 483 (4), 346 (8), 304 (16), 278 (6), 262 (45), 234 (31), 220
(24), 163 (13), 146 (31), 138 (24), 121 (100), 92 (41), 64 (17), 43
(66). C34H24N2O10 (620.6): calcd. C 65.80, H 3.87, N 4.52; found
C 65.82, H 4.18, N 4.43.
Photolysis of 1 with Anisaldehyde 2d: A solution of 1 (760 mg,
4 mmol) and 2d (1.36 g, 10 mmol) in benzene (80 mL) was photo-
lyzed for 3 h to reach a complete conversion of 1. Workup as de-
scribed above gave the products 3d (197 mg, 15%), 4d (219 mg,
17%), 5d (314 mg, 24%), 7 (167 mg, 22%), 8 (117 mg, 14%), and 9
(24 mg, 3%).
1-Acetyl-1,3-dihydro-3-(p-methoxybenzoyl)-2H-indol-2-one
(3d):
Thermal Decomposition of 6c: Heating of 6c (100 mg, 0.19 mmol)
absorbed on silica gel (10 g) on a steam bath and chromatographic
separation of the reaction mixture on a silica gel column afforded
3c (55 mg, 0.167 mmol, 58%) and 8 (20 mg, 0.097 mmol, 21%).
White powder (from petroleum ether and acetone), m.p. 138Ϫ139
°C. IR (KBr): ν˜ ϭ 2920, 1775, 1720, 1605, 1580, 1512, 1460, 1425,
1372, 1325, 1255, 1170, 1100, 1030, 1010, 915, 855, 800, 765, 700
1
cmϪ1. H NMR (CDCl3, 300 MHz): δ ϭ 2.75 (s, 3 H), 3.89 (s, 3
H), 6.26 (s, 1 H), 6.96 (d, J ϭ 8.6 Hz, 2 H), 7.22Ϫ7.47 (m, 3 H),
8.06 (d, J ϭ 8.6 Hz, 2 H), 8.31 (d, J ϭ 8.3 Hz, 1 H) ppm. MS: m/
z (%) ϭ 325 [Mϩ] (3), 152 (6), 135 (100), 132 (16), 104 (5), 92 (5),
77 (11), 43 (9). C18H15NO5 (325.3): calcd. C 66.46, H 4.62, N 4.31;
found C 66.42, H 4.60, N 4.46.
Reaction of 1 with 2c Induced by Thermal Decomposition of Benzoyl
Peroxide (BP): Heating of a benzene solution of BP (4.9368 g,
20.4 mmol), 1 (1.3608 g, 7.2 mmol), and 2c (3.7654 g, 26.8 mmol)
at reflux for 48 h resulted in the total conversion of 1, and the
mixture was separated by chromatography on a silica gel column
with petroleum ether and ethyl acetate as eluents and gave, in ad-
dition to biphenyl and benzoic acid derived from BP, 3c
(0.69 mmol, 10%), 4c (0.41 mmol, 12%), 5c (0.21 mmol, 6%), 6c
(1.80 mmol, 50%), 8 (0.31 mmol, 4%), and 9 (0.18 mmol, 3%).
(3R,3ЈR)-1,1Ј-Diacetyl-1,1Ј,3,3Ј-tetrahydro-3,3Ј-bis(p-methoxy-
benzoyl)-3,3Ј-bi-2H-indole-2,2Ј-dione (4d): Colorless crystals (from
petroleum ether and ethyl acetate) m.p. 147Ϫ148 °C. IR (KBr): ν˜ ϭ
2900, 1760, 1720, 1600, 1520, 1450, 1370, 1330, 1260, 1170, 1100,
1
1020, 940, 850, 760, 700, 600 cmϪ1. H NMR (CDCl3, 300 MHz):
X-ray Crystallographic Study. Crystal Data for 6a: C24H20N2O7,
δ ϭ 2.52 (s, 6 H), 3.88 (s, 6 H), 6.95Ϫ7.02 (m, 6 H), 7.10 (t, J ϭ
7.5 Hz, 2 H), 7.45 (td, J ϭ 7.8, 1.4 Hz, 2 H), 8.07Ϫ8.16 (m, 6 H),
8.24 (d, J ϭ 8.2 Hz, 2 H) ppm. MS: m/z (%) ϭ 459 (1), 304 (1),
262 (4), 220 (2), 152 (9), 135 (100), 107 (5), 92 (4). C36H28N2O10
(648.6): calcd. C 66.67, H 4.32, N 4.32; found C 66.76, H 4.63,
N 4.45.
M
ϭ
448.42, colorless prisms, EnrafϪNonius CAD4 dif-
˚
fractometer, Mo-Kα radiation (λ ϭ 0.71073 A), 0.45 ϫ 0.25 ϫ
0.05 mm, T ϭ 293(2) K. Monoclinic, space group P21/c, a ϭ
˚
7.6033(15), b ϭ 35.579(7), c ϭ 8.1527(16) A, α ϭ 90, β ϭ 104.19(3),
γ ϭ 90°, V ϭ 2138.1(7) A , Z ϭ 4, Dcalcd. ϭ 1.393 g·cmϪ3, µ ϭ
3
˚
0.104 mmϪ1, F(000) ϭ 936.00. The structure was solved by direct
methods (SHELXL) and refined on F2 by full-matrix, least-squares.
A total of 4409 independent reflections [R(int) ϭ 0.1495] were used
(3R,3ЈS)-1,1Ј-Diacetyl-1,1Ј,3,3Ј-tetrahydro-3,3Ј-bis(p-methoxy-
benzoyl)-3,3Ј-bi-2H-indole-2,2Ј-dione (5d): White powder (from
Eur. J. Org. Chem. 2004, 527Ϫ534
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
533

Y. Zhang, L. Wang, Y. Zhu, J.-H. Xu
FULL PAPER
[13e]
1953, 18, 1051Ϫ1054.
W. H. Urry, D. J. Trecker, H. D.
in the refinement, which converged with R ϭ 0.1410 and wR ϭ
0.2764 (GOF ϭ 1.057). CCDC-215369 contains the supplementary
crystallographic data for this paper. These data can be obtained
free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or
from the Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, UK; Fax: (internat.) ϩ 44-1223/336-
033; E-mail: deposit@ccdc.cam.ac.uk].
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This work was supported by the National Natural Science Foun-
dation of China (NSFC, 20072017) and the Specialized Research
Fund for the Doctoral Program of Higher Education (SRFDP,
20010284033). Partial support by the Modern Analytical Center at
Nanjing University is also gratefully acknowledged.
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