Light-induced geometric isomerization of 1,2-diphenylcyclopropanes included within Y zeolites: Role of Cation-guest binding

Article abstract of DOI:10.1021/jo026137k

Through a systematic study of several diphenylcyclopropane derivatives, we have inferred that the cations present within a zeolite control the excited-state chemistry of these systems. In the parent 1,2-diphenylcylopropane, the cation binds to the two phenyl rings in a sandwich-type arrangement, and such a mode of binding prevents cis-to-trans isomerization. Once an ester or amide group is introduced into the system (derivatives of 2β,3β-diphenylcyclopropane-1α-carboxylic acid), the cation binds to the carbonyl group present in these chromophores and such a binding has no influence on the cis-trans isomerization process. Cation-reactant structures computed at density functional theory level have been very valuable in rationalizing the observed photochemical behavior of diphenylcyclopropane derivatives included in zeolites. While the parent system, 1,2-diphenylcylopropane, has been extensively investigated in the context of chiral induction in solution, owing to its failure to isomerize from cis to trans, the same could not be investigated in zeolites. However, esters of 2β,3β-diphenylcyclopropane-1α-carboxylic acid could be studied within zeolites in the context of chiral induction. Chiral induction as high 20% ee and 55% de has been obtained with selected systems. These numbers, although low, are much higher than what has been obtained in solution with the same system or with the parent system by other investigators (maximum ～10% ee).

Full text of DOI:10.1021/jo026137k

VOLUME 67, NUMBER 25
DECEMBER 13, 2002
©
Copyright 2002 by the American Chemical Society
Ligh t-In d u ced Geom etr ic Isom er iza tion of
1
,2-Dip h en ylcyclop r op a n es In clu d ed w ith in Y Zeolites: Role of
Ca tion -Gu est Bin d in g†
‡
‡
§
‡
Lakshmi S. Kaanumalle, J . Sivaguru, R. B. Sunoj, P. H. Lakshminarasimhan,
§
,‡
J . Chandrasekhar, and V. Ramamurthy*
Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, and Department of Organic
Chemistry, Indian Institute of Science, Bangalore 560012, India
murthy@tulane.edu
Received J uly 3, 2002
Through a systematic study of several diphenylcyclopropane derivatives, we have inferred that
the cations present within a zeolite control the excited-state chemistry of these systems. In the
parent 1,2-diphenylcylopropane, the cation binds to the two phenyl rings in a sandwich-type
arrangement, and such a mode of binding prevents cis-to-trans isomerization. Once an ester or
amide group is introduced into the system (derivatives of 2â,3â-diphenylcyclopropane-1R-carboxylic
acid), the cation binds to the carbonyl group present in these chromophores and such a binding
has no influence on the cis-trans isomerization process. Cation-reactant structures computed at
density functional theory level have been very valuable in rationalizing the observed photochemical
behavior of diphenylcyclopropane derivatives included in zeolites. While the parent system, 1,2-
diphenylcylopropane, has been extensively investigated in the context of chiral induction in solution,
owing to its failure to isomerize from cis to trans, the same could not be investigated in zeolites.
However, esters of 2â,3â-diphenylcyclopropane-1R-carboxylic acid could be studied within zeolites
in the context of chiral induction. Chiral induction as high 20% ee and 55% de has been obtained
with selected systems. These numbers, although low, are much higher than what has been obtained
in solution with the same system or with the parent system by other investigators (maximum
∼
10% ee).
In tr od u ction
,2-Diphenylcyclopropane has played a central role in
excited (direct excitation or triplet sensitization), no cis-
to-trans isomerization resulted. As opposed to the pho-
tobehavior of the above parent system, upon direct
excitation and triplet sensitization, amides and esters of
4
1
the quest for new methods of asymmetric induction in
1
organic photochemistry. The optically inactive cis-1,2-
2
â,3â-diphenylcyclopropane-1R-carboxylic acid readily
diphenylcyclopropane can be transformed into its chiral
trans isomer by both singlet- and triplet-photosensitized
irradiations. Following the original report by Hammond
and Cole (ee 6.7%), the chiral induction on this isomer-
ization process has been investigated by at least five
independent research groups and the best ee obtained
thus far is 10% (Scheme 1).2 Therefore, cis-1,2-diphen-
ylcyclopropane suggested itself as a benchmark system
to examine the influence of the zeolite medium on the
chiral induction process. Surprisingly, when this molecule
was included within MY (M ) alkali ion) zeolite and
photoisomerized from cis to trans isomers within zeolites.
With the help of computations based on density func-
tional theory, we have traced this puzzling difference in
(
2) (a) Ouannes, C.; Beugelmans, R.; Roussi, G. J . Am. Chem. Soc.
1
973, 95, 8472. (b) Faljoni, A.; Zinner, K.; Weiss, R. G. Tetrahedron
,3
Lett. 1974, 13, 1127. (c) Ueno, A.; Toda, F.; Iwakura, Y. J . Polym. Sci.
Polym. Chem. Ed. 1974, 12, 1841. (d) Horner, L.; Klaus, J . Liebigs Ann.
Chem. 1979, 1232. (e) Vondenhof, M.; Mattay, J . Chem. Ber. 1990, 123,
2
1
457. (f) Inoue, Y.; Yamasaki, N.; Shimoyama, H.; Tai, A. J . Org. Chem.
993, 58, 1785.
(3) For reviews on asymmetric induction in organic photochemistry,
see: (a) Rau, H. Chem. Rev. 1983, 83, 535. (b) Inoue, Y. Chem. Rev.
992, 92, 741. (c) Pete, J . P. Adv. Photochem. 1996, 21, 135. (d) Everitt,
1
†
Dedicated to Professors R. G. Weiss and F. D. Lewis on the occasion
S. R. L.; Inoue, Y. In Molecular and Supramolecular Photochemistry;
Ramamurthy, V., Schanze, K. S., Eds.; Marcel Dekker: New York,
1999; p 71.
of their 60th birthdays.
‡
Tulane University.
Indian Institute of Science.
§
(4) Lakshminarasimhan. P.; Sunoj, R. B.; Chandrasekhar, J .; Ra-
mamurthy, V. J . Am. Chem. Soc. 2000, 122, 4815.
(1) Cole, R. S.; Hammond, G. S. J . Am. Chem. Soc. 1965, 87, 3256.
1
0.1021/jo026137k CCC: $22.00 © 2002 American Chemical Society
Published on Web 11/15/2002
J . Org. Chem. 2002, 67, 8711-8720
8711

Kaanumalle et al.
SCHEME 1
behavior between the parent, and the latter two systems
to the difference in the nature of the cation interaction
with these systems.
To appreciate the influence of zeolites on the photo-
isomerization of 1,2-diphenylcyclopropanes, a knowledge
of the structure of the Y zeolite and the nature of
interaction between cations present in the zeolites and
the guest molecules is essential. The internal structure
of the faujasite class of zeolites is characterized by a
three-dimensional network of “supercages” (large voids
ca. 13.6 Å in diameter within which adsorbed guest
molecules are located) interconnected by tetrahedrally
5
disposed “windows” (ca. 8 Å diameter, Figure 1). Charge-
compensating cations are located at three different sites
(types I, II, and III) within the zeolite framework of which
only the latter two are expected to be readily accessible
to the interior of the supercages and hence to the
adsorbed organic. The Y zeolite used in this study has
F IGURE 1. The structure of a supercage in which the organic
guest is presumed to reside. Eight of these supercages consti-
tute one unit cell of a X or Y zeolite. Cation locations are
indicated as type I, type II, and type III. Type II and type III
cations are present within the supercage, and type I is within
the sodalite cage.
6
only types I and II sites occupied.
A variety of techniques have demonstrated that ben-
zene and alkylated benzenes in NaY zeolite are prefer-
9
7
action of the cation with the nitro group. More impor-
entially adsorbed at the type II site inside the supercage.
tantly, in such cases, the cations are dislodged from their
original type II positions. Similar cation migration from
Cation-π interaction (also known as cation-quadrupolar
interaction)8 has been recognized by the zeolite com-
munity for over two decades as the main force of
interaction between aromatic guest molecules and the
zeolite supercage. Polar aromatic molecules such as
nitrobenzene are stabilized within NaY zeolite via inter-
(
7) (a) Mellot, C.; Simonot-Grange, M.-H.; Pilverdier, E.; Bellat, J .-
P.; Espinat, D. Langmuir 1995, 11, 1726. (b) Fitch, A. N.; J obic, H.;
Renouprez, A. J . Chem. Soc., Chem. Commun. 1985, 284. (c) Fitch, A.
N.; J obic, H.; Renouprez, A. J . Phys. Chem. 1986, 90, 1311. (d) J obic,
H.; Renouprez, A.; Fitch, A. N.; Lauter, H. J . J . Chem. Soc., Faraday
Trans. 1987, 83, 3199. (e) Goyal, R.; Fitch, A. N.; J obic, H. J . Chem.
Soc., Chem. Commun. 1990, 1152. (f) Klein, H.; Kirschhock, C.; Fuess,
H. J . Phys. Chem. 1994, 98, 12345. (g) Czjzek, M.; Fuess, H.; Vogt, T.
J . Phys. Chem. 1991, 95, 5255. (h) Pichon, C.; Methivier, A.; Grange,
M.-H. S.; Baerlocher, C. J . Phys. Chem. B 1999, 103, 10197. (i) Vitale,
G.; Mellot, C. F.; Bull, L. M.; Cheetham, A. K. J . Phys. Chem. B 1997,
101, 4559. (j) Yeom, Y. H.; Kim, A. N.; Kim, Y.; Song, S. H.; Seff, K. J .
Phys. Chem. B 1998, 102, 6071. (k) Pichon, C.; Methivier, A.; Grange,
M.-H. S.; Baerlocher, C. J . Phys. Chem. B 1999, 103, 10197.
(8) (a) Gokel, G. W.; De Wall, S. L.; Meadows, E. S. Eur. J . Org.
Chem. 2000, 17, 2967. (b) Ma, J . C.; Dougherty, D. A. Chem. Rev. 1997,
97, 1303. (c) Kim, K. S.; Tarakeshwar, P.; Lee, J . Y. Chem. Rev. 2000,
100, 4145. (d) Fujii, T. Mass Spec. Rev. 2000, 19, 111.
(5) (a) Van-Bekkum, H.; Flanigen, E. M.; J ansen, J . C. Introduction
to Zeolite Science and Practice; Elsevier: Amsterdam, 1991. (b) Dyer,
A. An Introduction to Zeolite Molecular Sieves; J ohn Wiley and Sons:
New York, 1988. (c) Breck, D. W. Zeolite Molecular Sieves: Structure,
Chemistry and Use; J ohn Wiley and Sons: New York, 1974.
(
6) (a) Shepelev, Y. F.; Butikova, I. K.; Smolin, Y. I. Zeolites 1991,
1
1
1
1, 287. (b) Shepelev, Y. F.; Andersen, A. A.; Smolin, Y. I. Zeolites 1990,
0, 61. (c) Takaishi, T. Zeolites 1996, 17, 389. (d) Olson, D. H. Zeolites
995, 15, 439. (e) Forano, C.; Slade, R. C. T.; Andersen, E. K.; Andersen,
I. G. K.; Prince, E. J . Solid State Chem. 1989, 82, 95. (f) Malek, A.;
Ozin, G. A.; Macdonald, P. M. J . Phys. Chem. 1996, 100, 16662. (g)
Yeom, Y. H.; J ang, S. B.; Kim, Y.; Song, S. H.; Seff, K. J . Phys. Chem.
B. 1997, 101, 6914.
(9) Kirschhock, C.; Fuess, H. Zeolites 1996, 17, 381.
8
712 J . Org. Chem., Vol. 67, No. 25, 2002

Light-Induced Geometric Isomerization of 1,2-Diphenylcyclopropanes
SCHEME 2
their original location has been established during the
adsorption of hydroflurocarbons within NaY.10 The main
reason for dislocation of cations from their original
positions is believed to be the strong cation-guest
molecule interaction. Examination of the literature on
guest adsorption within Y zeolites leads to two conclu-
sions of relevance to our investigation: (a) Cation-guest
interaction is important within zeolites. (b) On adsorption
of organic guest molecules, cations would move from their
original locations and provide a stronger interaction (than
the cation zeolite wall interaction) between the cation and
the guest molecule results.
derivatives 1c and 1f gave the corresponding trans
isomers in ∼20% enantiomeric excess (ee). In the second
approach, the achiral zeolite MY was used as such, but
the reactant was connected to a chiral perturber via a
covalent bond (chiral auxiliary approach).11 This chiral
auxiliary approach with optically pure menthyl ester of
2â,3â-diphenylcyclopropane-1R-carboxylic acid 1g gave
the trans isomer in 55% diastereomeric excess. Admit-
tedly, the enantiomeric excess (ee) and diastereomeric
excess (de) obtained are at best moderate, but these are
the highest among the cis-1,2-diphenylcyclopropane sys-
tems examined thus far in any media. Considering that
the same systems in solution give zero % ee and very
low de (<5%), the results presented here on achiral cis-
1,2-diphenylcyclopropane and 2â,3â-diphenylcyclopro-
pane-1R-carboxylic acid derivatives (amides and esters)
and chiral esters of 2â,3â-diphenylcyclopropane-1R-car-
boxylic acid are significant. Further, our current goal is
to show that while 1,2-diphenylcyclopropane failed to
geometrically isomerize within a zeolite, isomerization
and chiral induction of closely related systems can be
achieved from the latter systems in this medium.
The fact that 2â,3â-diphenylcyclopropane-1R-carboxylic
acid derivatives behaved differently from the parent
system allowed us to reach our initial goal of examining
the use of a confined space (zeolite) on chiral induction
during the photoisomerization of cis-diphenylcyclopro-
pane derivatives to the trans isomer (Scheme 2). We
present our results on several esters and amides of 2â,3â-
diphenylcyclopropane-1R-carboxylic acid. The goal is to
identify the origin of differences in photobehavior be-
tween 1,2-diphenylcyclopropane and 2â,3â-diphenylcy-
clopropane-1R-carboxylic acid derivatives within zeolites
and to show that chiral induction can be obtained with
these systems within zeolites. In the context of chiral
induction, we have utilized two approaches. In one,
achiral zeolite MY was modified by including an optically
pure organic molecule as an adsorbent (chiral inductor)
Resu lts
The photochemistry of cis-1,2-diphenylcyclopropane 1a
and nine 2â,3â-diphenylcyclopropane-1R-carboxylic acid
derivatives 1b-j was investigated within MY zeolites
(Scheme 2). Triplet sensitization was performed (450 W
medium-pressure mercury lamp with Pyrex filter) with
1
1
within a zeolite. In this case, achiral benzyl amide (1c)
and the ethyl ester (1f) of 2â,3â-diphenylcyclopropane-
4
′-methoxyacetophenone as the sensitizer. Although the
1
R-carboxylic acid were used as probe reactants. The
exact triplet energies of cis and trans isomers of 1 are
unknown, they are expected to be lower than that of 4′-
(
10) (a) Lim, K. H.; Grey, P. C. J . Am. Chem. Soc. 2000, 122, 9768.
(
b) Lim, K. H.; J ousse, F.; Auerbach, S. M.; Grey, C. P. J . Phys. Chem
12
methoxyacetophenone (∼71 kcal/mol). As reported in
B 2001, 105, 9918. (c) J aramillo, E.; Grey, C. P.; Auerbach, S. M. J .
Phys. Chem. B 2001, 105, 12319. (d) Grey, P. C.; Poshini, I. F.;
Gualtieri, A. F.; Norby, P.; Hanson, J . C.; Corbin, D. R. J . Am. Chem.
Soc. 1997, 119, 1981. (e) Norby, P.; Poshini, F. I.; Gualtieri, A. F.;
Hanson, J . C.; Grey, C. P. J . Phys. Chem. B 1998, 102, 839.
the literature, triplet sensitization of 1,2-diphenylcyclo-
propane in acetonitrile solution gave a photostationary
state mixture consisting of both cis and trans isomers
(
11) (a) Sivaguru, J .; Shailaja, J .; Uppili, S.; Ponchot, K.; J oy, A.;
Arunkumar, N.; Ramamurthy, V. Organic Solid State Reactions; Toda,
F., Ed.; Kluwer Academic Press: Norwell, MA, 2002; p 159. (b)
Shailaja, J .; Sivaguru, J .; Uppili, S.; J oy, A.; Ramamurthy, V. Mirco-
porous Mesoporous Mater. 2001, 48, 319. (c) J oy, A.; Ramamurthy, V.
ChemsEur. J . 2000, 6, 1287.
(12) (a) Hammond, G. S.; Wyatt, P.; DeBoer, C. D.; Turro, N. J . J .
Am. Chem. Soc. 1964, 86, 2532. (b) Becker, R. S.; Edwards, L.; Bost,
R.; Elam, M.; Griffinn, G. J . Am. Chem. Soc. 1972, 94, 6584. (c) Karki,
S. B.; Dinnocenzo, J . P.; Farid, S.; Goodman, J .; Gould, I. R.; Zona, T.
A. J . Am. Chem. Soc. 1997, 119, 431.
J . Org. Chem, Vol. 67, No. 25, 2002 8713

Kaanumalle et al.
TABLE 1. Cis/Tr a n s Ra tio a t th e P h otosta tion a r y Sta te
TABLE 3. Dia ster eom er ic Excess Obta in ed in P r od u ct
2g-j d u r in g th e Tr ip let-Sen sitized P h otoisom er iza tion of
Ch ir a l Der iva tives of 2â,3â-Dip h en ylcyclop r op a n e-1r-
ca r boxylic Acid 1g-j
u p on Tr ip let Sen sitiza tion (4′-Meth oxya cetop h en on e) of
1
,2-Dip h en ylcyclop r op a n e a n d 2,3-Dip h en ylcyclop r op a n e
a
Der iva tives
diphenylcyclopropane derivativesb
MY-zeolite
2g % de
2h % de
2ib % de
2j % de
b
medium
1a
1b
1c
1d
1e
LiY
NaY
KY
50-B
55-B
30-B
22-B
5-B
25-A
40-A
6-A
5-A
3-A
12-A
32-B
7-A
5-A
2-A
7-B
16-A
4-B
2-B
2-B
4-B
solution
LiY
NaY
KY
RbY
CsY
45:55
95:5
92:8
88:12
85:15
65:35
48:52
12:88
40:60
35:65
33:67
55:45
50:50
11:89
35:65
58:42
55:45
56:44
35:65
10:90
21:79
38:62
40:60
41:59
39:61
45:55
39:61
40:60
39:61
37:63
RbY
CsY
solutiona
4-B
5-B
5-B
a
Dichloromethane/hexane as solvent. b Loading in KY, RbY,
and CsY were 50-70%.
a
The photostationary state ratios are based on starting from
pure cis and pure trans isomers. Average of at least three
independent runs from each isomer. b For structures, see Scheme
diphenylcyclopropane-1R-carboxylic acid (1g-j) were in-
cluded within MY zeolites (1 molecule per 10 supercages)
and irradiated. As expected, the trans isomer resulted
and the de obtained in the product within NaY varied
between 16 and 55% (Table 3).
To gain a better insight on the role of cations (present
within zeolite supercages) on the observed photobehavior
of cis-1,2-diphenylcyclopropane, density functional theory
2
.
TABLE 2. En a n tiom er ic Excess Obta in ed in P r od u ct 2
d u r in g th e Tr ip let-Sen sitized P h otoisom er iza tion of
Ach ir a l Der iva tives of 2â,3â-Dip h en ylcyclop r op a n e-1r-
ca r boxylic Acid (F or Str u ctu r es, See Sch em e 2)
chiral inductor
ephedrine
pseudoephedrine
norephedrine
diethyl tartrate
cyclohexylethylamine
2b % ee 2c % ee 2d % ee 2f % ee
8
8
5
-
20
15
15
-
2
2
3
-
0
5
5
12
17
(
DFT) calculations on cation binding to cis-1,2-diphenyl-
1
3
cyclopropane were carried out. The polarized 6-31G*
basis set was used for C, H, Li, Na, and K. Interaction
energies of cations were determined on the basis of gas-
phase optimized geometries of metal ion complexes with
cis-1,2-diphenylcyclopropane. Intuitively, binding of metal
ions is expected to be higher with the substrate when it
interacts simultaneously with two phenyl rings. Thus,
we have chosen initial guess geometry for the cis-1,2-
diphenylcyclopropane with the metal ion positioned
between the two phenyl rings. During the calculation,
the cations were free to move to find the most stable
position. Calculations did not include any structural
moiety from the zeolite. In the case of cis-1,2-diphenyl-
cyclopropane a geometry-optimized structure obtained
upon metal ion complexation is shown in Figure 2. Alkali
metal ions are calculated to have a strong interaction
with cis-1,2-diphenylcyclopropane. The computed values
reveal a regular gradation from lithium to potassium ion.
Interaction energies calculated for metal ion binding to
two benzene molecules in the sandwich arrangement are
0
0
0
(45% cis and 55% trans; 4′-methoxyacetophenone as
1
2
sensitizer in acetonitrile). Almost similar photostation-
ary state ratios were obtained with 2â,3â-diphenylcyclo-
propane-1R-carboxylic acid derivatives 1b-e (Table 1).
For zeolite irradiations, both triplet sensitizer (4′-
methoxyacetophenone) and 1 were included within alkali
+
+
+
+
+
cation (Li , Na , K , Rb , and Cs ) exchanged Y zeolites.
All photostationary state measurements were made from
both pure trans- and cis-1a -e. The photostationary state
compositions of 1a -e included in MY zeolites are given
in Table 1. Examination of Table 1 reveals two distinct
trends: (a) In the case of 1a the cis isomer is preferred
inside the zeolite. The amount of the cis isomer at the
photostationary state depends on the nature of the
exchanged cation. (b) Amides and esters of 2â,3â-di-
phenylcyclopropane-1R-carboxylic acid (1b-e) show a
different behavior. In these cases, the cis isomer is no
longer favored and the photostationary state ratio is
much closer to that in solution.
+
closer for all alkali ions except Li as in cis-1,2-diphen-
ylcyclopropane complexes (interaction energy at MP2
+
+
level for sandwich arrangement: Li , -81.1; Na , -56.2;
+
14
and K , 32.3 kcal/mol). When comparing the binding
energies of cations to two benzenes in a sandwich
arrangement with that to cis-1,2-diphenylcyclopropane
one should keep in mind that entropy also plays an
important role in the overall free energy of binding of
The possibility of photoisomerization of the cis isomers
of the amides and esters of 2â,3â-diphenylcyclopropane-
1
R-carboxylic acid (1b-e) within zeolites provided an
opportunity to examine the influence of chiral inductors
during photoisomerization of achiral cyclopropanes 1c
and 1f. Chiral induction during photoisomerization was
monitored by either GC or HPLC by directly irradiating
the cyclopropanes 1c and 1f within chirally modified NaY
zeolite, and the results are presented in Table 2. Low but
significant ee was obtained with several chiral inductors.
The maximum ee obtained in the case of 1c was with
ephedrine (20%) and in the case of 1f was with cyclo-
hexylamine (17%). The opposite enantiomers were formed
with equal ee when the optical antipode of the chiral
inductor was used, indicating that the systems are well
behaved. To examine the influence of the zeolite on a
system with a chiral auxiliary, optically pure menthyl,
neomenthyl, isomenthyl, and fenchyl esters of 2â,3â-
(13) Frisch, M. J .; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J . R.; Zakrzewski, V. G.; Montgomery, J . A.,
J r.; Stratmann, R. E.; Burant, J . C.; Dapprich, S.; Millam, J . M.;
Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J .;
Barone, V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo,
C.; Clifford, S.; Ochterski, J .; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J . B.; Cioslowski, J .; Ortiz, J . V.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R. L.;
Fox, D. J .; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.;
Gonzalez, C.; Challacombe, M.; Gill, P. M. W.; J ohnson, B.; Chen, W.;
Wong, M. W.; Andres, J . L.; Gonzalez, C.; Head-Gordon, M.; Replogle,
E. S.; Pople, J . A. Gaussian 98, Revision A.6; Gaussian, Inc.: Pitts-
burgh, PA, 1998.
(14) Thomas, K. J .; Sunoj, R. B.; Chandrasekhar, J .; Ramamurthy,
V. Langmuir 2000, 16, 4912.
8
714 J . Org. Chem., Vol. 67, No. 25, 2002

Light-Induced Geometric Isomerization of 1,2-Diphenylcyclopropanes
behavior between cis-1,2-diphenylcyclopropane and the
amides and esters of 2â,3â-diphenylcyclopropane-1R-
carboxylic acid. Within a zeolite, the cations are bound
to oxygens on the framework. As a result, the metal ions
are likely to interact less effectively than when they are
free. Nevertheless, one should note that the cations
present in the zeolites have been established to move
from their original locations provided the binding with
the guest molecules is stronger.9
,10
Given the large
computed interaction energies, the cations moving from
their original location to interact with diphenylcyclopro-
panes in the geometries shown in Figures 2-4 is likely.
While one might question the validity of using gas-phase
computational data to understand the chemistry that
occurs within a more complex environment, we believe
that this is a good starting point.
Discu ssion
The most important point we wish to address in this
section is the difference in the photobehavior between
cis-1,2-diphenylcyclopropane and the amides and esters
of 2â,3â-diphenylcyclopropane-1R-carboxylic acid within
a zeolite. In solution, cis-1,2-diphenylcyclopropane un-
dergoes geometric isomerization from the excited singlet
and triplet states. The photoisomerization from the
excited singlet state is accompanied by other reactions,
and therefore, prolonged irradiation results in the loss
of 1,2-diphenylcyclopropane.16 However, triplet sensitiza-
tion is clean and establishes a photostationary state
between the cis and trans isomers without any side
reactions.12 A similar behavior was observed with the
amides and esters of 2â,3â-diphenylcyclopropane-1R-
carboxylic acid 1b-e. In solution, all systems investi-
gated in this study (1a -g) underwent geometric isomer-
ization upon direct excitation and triplet sensitization.
The photostationary state (cis/trans ratio) in solution
varied between 50:50 and 35:65 (Table 1). In contrast to
the solution behavior, in LiY and NaY cis-1,2-diphenyl-
cyclopropane (1a ) failed to isomerize to the trans isomer
both upon direct excitation and triplet sensitization. The
photostationary state essentially contained only the cis
isomer (Table 1). On the other hand, amides and esters
of 2â,3â-diphenylcyclopropane-1R-carboxylic acid (1b -
g) upon triplet sensitization in zeolites establish a
photostationary state containing both cis and trans
isomers. A minor point to note is that in LiY the
photostationary state in the case of the amides 1b-d is
in favor of the trans isomer. Clearly, the cis isomers of
the amides and esters of 2â,3â-diphenylcyclopropane-1R-
carboxylic acid isomerize readily to the trans within MY
zeolites, a behavior not expected on the basis of the
chemistry of cis-1,2-diphenylcyclopropane.
F IGURE 2. B3LYP/6-31G*-optimized geometry of cis-diphen-
+
ylcyclopropane and its complex with Na ion. Binding affinities
+
+
+
with Li , Na , and K are also included.
cations to substrates. For example, while the experimen-
tal enthalpy of binding of the two benzene molecules to
+
K
is 35 kcal/mol, the free energy of binding is only 21
1
5
kcal/mol. The large reduction in entropy makes binding
of two benzene molecules quite unfavorable. On the other
hand, since the host cavity of cis-1,2-diphenylcyclopro-
pane is predesigned to accept a cation, such a large
reduction in binding free energy is not expected. There-
fore, one might anticipate that cis-1,2-diphenylcyclopro-
pane to have a much larger free energy of binding than
that of the two benzene molecules binding to a cation.
+
+
+
Computations on cation (Li , Na , and K ) binding to
the methyl amide of 2â,3â-diphenylcyclopropane-1R-
carboxylic acid and the methyl ester of 2â,3â-diphenyl-
cyclopropane-1R-carboxylic acid were performed at the
RB3LYP/6-31G* level using the Gaussian 98 package.13
In these cases, the structures of methyl amide of 2â,3â-
diphenylcyclopropane-1R-carboxylic acid and the methyl
ester of 2â,3â-diphenylcyclopropane-1R-carboxylic acid
were optimized first. Using these structures, the interac-
tion energies with cations were estimated by placing the
cations at various positions near the structure. During
the calculations, the cations were free to move. Interest-
ingly, in these two cases, in addition to a structure
corresponding to cation-cis-diphenyl binding (similar to
Figure 2b), several others were found in which the cation
is bound either solely to the amide or the ester or
cooperatively to the amide/ester and a phenyl group.
These structures are illustrated in Figures 3 and 4. More
importantly, in each case at least one structure is equally
stable than the one in which the cation is bound to the
cis-diphenyl groups. Although we cannot be certain of the
structure being preferred within a zeolite, it is clear that
the presence of amide and ester groups offer additional
choices for the alkali ion.
We adopt the following model to understand the
difference in the photobehavior between cis-1,2-diphen-
ylcyclopropane and the amides and esters of 2â,3â-
diphenylcyclopropane-1R-carboxylic acid. The triplet-
sensitized geometric isomerization of 1,2-diphenylcy-
clopropanes is triggered by the cleavage of the PhCsCPh
bond (â CsC bond with respect to the phenyl group)
followed by rotation of one of the bonds substituted with
The above gas-phase computational data are very
valuable in understanding the difference in the photo-
(
16) (a) Valyocsik, E. W.; Sigal, P. J . Org. Chem. 1971, 36, 66. (b)
(
15) Sunner, J .; Nishizawa, K.; Kebarle, P. J . Phys. Chem. 1981,
Griffin, G. W.; Covell, J .; Petterson, R. C.; Dodson, R. M.; Klose, G. J .
Am. Chem. Soc. 1965, 117, 1410.
8
5, 1814.
J . Org. Chem, Vol. 67, No. 25, 2002 8715

Kaanumalle et al.
+
F IGURE 3. B3LYP/6-31G*-optimized geometries of complexes of Li ion with methyl amide of 2â,3â-diphenylcyclopropane-1R-
+
+
+
carboxylic acid. Binding affinities with Li , Na , and K are also included. Note the difference in the location of cation in the two
structures and the difference in binding affinities between them.
the phenyl group. As illustrated in Scheme 3, both cis
and trans isomers would be expected to give the same
diradical intermediate that would decay to the cis and
trans isomers at a fixed ratio independent of its origin.17
The photostationary state, in addition to the decay ratio
in the absence of any perturbation on the excited singlet
state, the triplet energies are also likely to be the same
both in solution and in zeolites. Based on this, we believe
the excitation ratio within the zeolites to be more likely
the same as in solution. To examine the influence of the
zeolite on the decay ratio of the diradical intermediate,
we generated the same diradical (singlet) intermediate
by photolyzing γ-2,4-diphenyl butyrolactone included in
NaY.18 Photolysis of γ-2,4-diphenyl butyrolactone gave
both cis- and trans-1,2-diphenylcyclopropane in equal
amounts both in solution and in NaY zeolite suggesting
that the diradical intermediate once generated decays to
both cis and trans isomers. Such a rationalization leads
us to believe that the enrichment of the cis isomer at the
photostationary state in the case of 1,2-diphenylcyclo-
propane within zeolites is related to the presence of a
barrier between the vertically excited cis-1,2-diphenyl-
cyclopropane and the twisted diradical state (Figure 5).
The barrier primarily arises from the cooperative inter-
action of alkali ion with the cis-phenyl groups. This model
is supported by the computed structure for alkali ion
bound cis-1,2-diphenylcyclopropane (Figure 2). Large
interaction energies have been computed at the B3LYP
level for binding of Li and Na to cis-1,2-diphenylcyclo-
propane (Figure 2). Any motion that would disrupt the
cooperative interaction of the alkali ion to the cis-phenyl
groups will have to surmount a barrier both in the ground
and excited states. Since conversion from the cis geom-
etry to the diradical intermediate involves such a disrup-
tion this process is expected to have a barrier in the
excited state within a zeolite. Consistent with the pos-
tulate that cation is most important for the cis enrich-
ment within zeolites, inclusion of water (a better coor-
(relative rates of ring closure of the diradical intermediate
to the cis and trans isomers), will also be determined by
the ease with which the diradical intermediate is formed
from the two isomers. With sensitizers such as 4′-meth-
oxyacetophenone having triplet energy above that of both
isomers (under which conditions the excitation ratio is
one), the photostationary state will be determined only
by the decay ratio. The fact that the photostationary state
in solution consists of both isomers suggests that there
is no preferential decay of the diradical intermediate to
any one isomer.
Enrichment of the cis isomer at the photostationary
state during triplet sensitization of 1,2-diphenylcyclo-
propane within zeolites could be due to changes in any
one (or all) of the following factors with respect to that
in solution: (a) the decay ratio, (b) the excitation ratio,
and (c) the relative rates of cleavage and isomerization
with respect to other processes. Since there are no
changes in the absorption spectra (diffuse reflectance
mode) for the two isomers between solution and zeolite,
we assume that the cation complexation will have no
influence on the excited-state energies of the two isomers.
We recognize that the absorption spectra provide infor-
mation only about the excited singlet states. However,
+
+
(17) Irradiations of pure diastereomers of the trans isomer of
R-methylbenzyl amide of 2â,3â-diphenylcyclopropane-1R-carboxylic
acid have shown that upon triplet sensitization a common intermediate
results that leads to racemization while upon direct excitation leads
to an intermediate where the diastereomers do not interconvert.
Sivaguru, J .; Shichi, T.; Ramamurthy, V. Org. Lett. 2002, 4, 4221-
4
224.
(18) Givens, R. S.; Oettle, W. F. J . Org. Chem. 1972, 37, 4325.
8
716 J . Org. Chem., Vol. 67, No. 25, 2002

Light-Induced Geometric Isomerization of 1,2-Diphenylcyclopropanes
benzocrown ether units present on the two phenyl groups
of the azobenzene unit.
From the above discussion, one would expect that
removal of the cation from the diphenyl “bowl” would
prompt the diphenylcyclopropane systems to isomerize
from cis to trans geometry. The photobehavior of the
amides and esters of 2â,3â-diphenylcyclopropane-1R-
carboxylic acid is consistent with this expectation. The
difference in behavior between amides and esters of
2
â,3â-diphenylcyclopropane-1R-carboxylic acid and 1,2-
diphenylcyclopropane could be understood based on the
computed geometries for Li -bound methyl amide and
+
methyl ester of 2â,3â-diphenylcyclopropane-1R-carboxylic
acid (Figures 3 and 4). Of the various computed struc-
tures two shown in Figures 3 and 4 suffice for the current
discussion. In the case of the amide, the metal ion prefers
to interact directly with the carbonyl oxygen (Figure 3)
while in the case of the ester the cation prefers to bind
to the ester oxygens (Figure 4). Strong dipolar interaction
of the alkali ions with carbonyls has been established in
the literature.21 In esters, the O, O interaction of the type
2
2
shown in Figure 4 is also known. The interaction
+
energies of Li to the ester and amide groups are much
larger than that of alkali ions to cis-diphenyl groups. In
+
+
the case of Na and K the differences in energy between
the two structures shown in Figures 3 and 4 are small.
An important point to note is that when the alkali ion
binds to the carbonyl chromophore the face of the alkali
ion that is still free can interact with the zeolite wall.
Such bindings (carbonyl- - -alkali ion- - -zeolite wall) are
expected to be much more stable than the alkali ion
interacting with two phenyl groups in a sandwich ar-
rangement. This reasoning leads us to believe that within
zeolites the cations interact with the amide and ester
groups of 2â,3â-diphenylcyclopropane-1R-carboxylic acid
derivatives rather than with the cis-diphenyl group. Such
interactions would not impose a barrier for rotation of
the cis-diphenyl to the diradical intermediate. The above
rationalization is based on the assumption that within
zeolites the photobehavior of the included diphenylcy-
clopropane is controlled by the cation-guest interaction.
Such an interaction would require the cation to move
from the original location (type II) and guest induced
relocation of cations has been documented in the litera-
ture.9 We recognize that our model will gain strength
only if we provide experimental support for the proposed
structures within zeolites. We hope to provide such data
in the future.
F IGURE 4. B3LYP/6-31G*-optimized geometries of complexes
+
of Li ion with methyl ester of 2â,3â-diphenylcyclopropane-
+
+
+
1
R-carboxylic acid. Binding affinities with Li , Na , and K
are also included. Note the difference in the location of cation
in the two structures and the difference in binding affinities
between them.
dinator to the cation) within LiY resulted in a photo-
stationary state similar to that in solution (cis:trans, 49:
5
1). Further, the cis: trans ratio in dry zeolites is
,10
+
dependent on the nature of cation. Cations such as Cs ,
which has a very small value of interaction energy, give
much less cis (65%) in the photostationary state than Li
+
(95%). Consistent with the literature reports that alkali
ions have smaller interaction energy with benzonitrile
The final aspect of this paper deals with the observed
enantio- and diastereoselectivities within zeolites (Tables
2 and 3). The enantiomeric excess observed although low
is consistent with our observations with most systems
where 20-40% ee seemed to be the norm (highest ee we
+
(
compare benzene- - -Na , -27.1 kcal/mol, and benzoni-
+
19
trile- - -Na , -15.7 kcal/mol), irradiation of 1-(4-cyano-
phenyl)-2-phenylcyclopropane included in NaY gave a
photostationary state consisting of both cis (56%) and
trans (44%) isomers. Our observations with 1,2-diphen-
ylcyclopropane are along the lines reported for azobis-
(21) (a) Smith, S. F.; Chandrasekhar, J .; J orgensen, W. L. J . Phys.
Chem. 1982, 86, 3308. (b) Raber, D. J .; Raber, N. K.; Chandrasekhar,
J .; Schleyer, P. V. R. Inorg. Chem. 1984, 23, 4076. (c) Ha, T.; Wild, U.
P.; K u¨ hne, R. O.; Loesch, C.; Schaffhauser, T.; Stachel, J .; Wokaun, A.
1978, 61, 1193. (d) Del Bene, J . E. Chem. Phys. 1979, 40, 329. (e) Del
Bene, J . E.; Frisch, M. J .; Raghavachari, K.; Pople, J . A.; Schleyer, P.
V. R. J . Phys. Chem. 1983, 87, 73.
benzocrown ether) systems.20 In these systems, the alkali
(
ions suppress the thermal isomerization of the cis isomer
to the trans form, and this phenomenon is attributed to
the “tying effect” of alkali ions by coordinating to the
(
22) (a) J ockusch, R. A.; Lemoff, A. S.; Williams, E. R. J . Phys. Chem.
(
19) (a) Mecozzi, S.; West, A. P. J .; Dougherty, D. A. J . Am. Chem.
A 2001, 105, 10929. (b) J ockusch, R. A.; Price, W. D.; Williams, E. R.
J . Phys. Chem. A 1999, 103, 9266. (c) J ockusch, R. A.; Lemoff, A. S.;
Williams, E. R. J . Am. Chem. Soc. 2001, 123, 12255. (d) Hoyau, S.;
Ohanessian, G. Chem. Eur. J . 1998, 4, 1561. (e) Dunbar, R. C. J . Phys.
Chem. A 2000, 104, 8067.
Soc. 1996, 118, 2307. (b) Mecozzi, S.; West, A. P. J .; Dougherty, D. A.
Proc. Natl. Acad. Sci. U.S.A. 1996, 93, 10566.
(
20) Shinkai, S.; Nakaji, T.; Ogawa, T.; Shigematsu, K.; Manabe,
O. J . Am. Chem. Soc. 1981, 103, 111.
J . Org. Chem, Vol. 67, No. 25, 2002 8717

Kaanumalle et al.
SCHEME 3
F IGURE 5. Proposed potential energy surface diagram for
triplet-sensitized isomerization of 1,2-diphenylcyclopropane
within cation-exchanged Y zeolite. Cation interaction with the
cis isomer results in a barrier for rotation of the cis isomer in
the excited state.
F IGURE 6. Schematic representation of the visualization of
asymmetric induction in solution, confined media, and confined
media with cations.
between the chiral center and the site of reaction present
within a single molecule. Figure 6 is a schematic repre-
sentation of the model we employ to visualize zeolite’s
ability to enhance the power of a chiral auxiliary. The
very low diastereomeric excess (<5%) for most cases in
solution suggests that the conformation of the reactant
molecule is likely to be such that the chiral auxiliary and
the reactive site of the molecule are far apart (Figure 6a).
On the other hand, within the confined space of a zeolite
the adoption of a folded conformation by the reactant
brings its reactive site closer to the chiral auxiliary
(Figure 6b). Cation presence within a zeolite besides
restricting the conformational flexibility of the chiral
auxiliary binds it closer to the reaction center (Figure
have observed is in the case of tropolone 2-phenyl ethyl
ether, 78%).23 An important point to note is that the two
systems investigated here give the product as a racemic
mixture in solution. It is obvious that the zeolite environ-
ment capable of forcing a stronger interaction between
the chiral inductor and the reactant diphenylcyclopro-
pane derivative. The diastereoselectivity observed with
menthyl ester is moderate (the highest de we have
observed is in tropolone systems, 88%).24 The zeolite
interior clearly is able to enhance the power of a chiral
auxiliary. In doing so, both the confined space as well as
the cation present in a zeolite are used effectively by the
zeolite. The cation and confined space coerce the molecule
to adopt a geometry resulting in a stronger interaction
(24) (a) Arunkumar, N.; Wang, K.; Ramamurthy, V.; Scheffer, J . R.;
Patrick, B. R. Org Lett. 2002, 4, 1443. (b) Sivaguru, J .; Scheffer, J . R.;
Chandrasekhar, J .; Ramamurthy, V. J . Chem. Soc., Chem. Commun.
2002, 830. (c) Uppili, S. Ramamurthy, V. Org Lett. 2002, 4, 87. (d)
Chong, K. C. W.; Sivaguru, J .; Shichi, T.; Yoshimi, Y.; Ramamurthy,
V.; Scheffer, J . R. J . Am. Chem. Soc. 2002, 124, 2858. (e) Cheung, E.;
Chong, K. C. W.; Sivaguru, J .; Ramamurthy, V.; Scheffer, J . R.; Trotter,
J . Org Lett. 2000, 2, 2801. (f) J oy, A.; Uppili, S.; Netherton, M. R.;
Scheffer, J . R.; Ramamurthy, V. J . Am. Chem. Soc. 2000, 122, 728. (g)
Chong, K. C. W.; J ayaraman, S.; Shichi, T.; Yoshimi, Y.; Ramamurthy,
V.; Scheffer, J . R. J . Am. Chem. Soc. 2002, 124, 2858. (h) J ayaraman,
S.; Uppili, S.; Natarajan, A.; J oy, A.; Chong, K. C. W.; Netherton, M.
R.; Zenova, A.; Scheffer, J . R.; Ramamurthy, V.Tetrahedron Lett. 2000,
41, 8231.
(
23) (a) Leibovitch, M.; Olovsson, G.; Sundarababu, G.; Ramamur-
thy, V.; Scheffer, J . R.; Trotter, J . J . Am. Chem. Soc. 1996, 118, 1219.
b) Sundarababu, G.; Leibovitch, M.; Corbin, D. R.; Scheffer, J . R.;
(
Ramamurthy, V. J . Chem. Soc., Chem. Commun. 1996, 2159. (c) J oy,
A.; Robbins, R. J .; Pitchumani, K.; Ramamurthy, V. Tetrahedron Lett.
1
997, 8825. (d) J oy, A.; Scheffer, J . R.; Corbin, D. R.; Ramamurthy, V.
J . Chem. Soc., Chem. Commun. 1998, 1379. (e) J oy, A.; Corbin, D. R.;
Ramamurthy, V. In Proceedings of 12th International Zeolite Confer-
ence; Traecy, M. M. J ., Marcus, B. K., Bisher, B. E., Higgins, J . B.,
Eds.; Materials Research Society: Warrendale, PA, 1999; p 2095. (f)
J oy, A.; Scheffer, J . R.; Ramamurthy, V. Org. Lett. 2000, 2, 119.
8
718 J . Org. Chem., Vol. 67, No. 25, 2002

Light-Induced Geometric Isomerization of 1,2-Diphenylcyclopropanes
c). Weak interactions between chiral auxiliary, cation
6
acetonitrile and the mass balance was checked by GC using
tetradecane as the calibration compound. All the product
recoveries had a mass balance of more than 90%.
Ch ir a l In d u ction Stu d ies w ith in Zeolites. (a ) Th e
Ch ir a l In d u ctor Ap p r oa ch : En a n tioselectivity. Chiral
inductor (20-25 mg) and compound (1c and f, 2-3 mg) were
dissolved in 0.5 mL of dichloromethane followed by the
addition of 15 mL of hexanes. NaY zeolite (300 mg) activated
at 500 °C was added with stirring. The slurry was stirred for
12 h, filtered, and washed thoroughly with fresh hexanes
and reaction site play an important role in the overall
asymmetric induction process within a zeolite.
Results presented in this paper suggest that one can
influence the excited-state behavior of organic molecules
through alkali ion binding.25 In this context, zeolites with
a reservoir of cations, only partially coordinated to the
zeolite framework, can be very useful. Although we have
no direct spectral evidence in favor of cation-guest
interaction in the systems investigated here, existence
of such interactions have been demonstrated previously
in other systems.7
(analysis of the supernatant showed absence of reactant and
chiral inductor). The loading level of the cyclopropane was kept
at one molecule for every 10 supercages (〈S〉 ) 0.1). A higher
ratio of the chiral inductor was employed to maximize the
chances of every reactant molecule being adjacent to a chiral
inductor within the supercage. The zeolite was dried under
-10
Exp er im en ta l Section
-
3
vacuum (2 × 10 Torr) at 60 °C for 6-8 h. The sample was
transferred into a quartz test tube inside a drybox and fresh
anhydrous hexanes was added, the test tube stoppered with
a rubber septum and wrapped with Parafilm. The slurry was
then irradiated (unfiltered output from a 450 W medium
pressure mercury lamp), filtered, and washed again with fresh
hexanes (analysis of the supernatant showed absence of
reactants and products). The reactant and the photoproducts
were extracted from the zeolite by stirring with acetonitrile.
The extract was concentrated, and the reactant and its
photoproducts were purified by a microcolumn with silica gel
using hexane/ethyl acetate as eluent. The extract was then
concentrated and analyzed on a chiral column (GC/HPLC). The
authentic samples (photoproducts independently synthesized)
were injected in the GC/HPLC and verified with the retention
times of the photoproducts.
Ma ter ia ls. NaY zeolite was obtained from Zeolyst Inter-
national, The Netherlands. Monovalent cation-exchanged zeo-
lites (LiY, KY, RbY, and CsY) were prepared by stirring 10 g
of NaY with 100 mL of a 10% solution of the corresponding
metal nitrate in water for 24 h with continuous refluxing. The
zeolite was filtered and washed thoroughly with distilled
water. This procedure was repeated three times. Subsequently,
the zeolite was dried at 120 °C for about 3 h to obtain the
cation-exchanged zeolite.
Syn th esis of Am id es a n d Ester s of 2,3-Dip h en ylcyclo-
p r op a n e-1-ca r boxylic Acid . 2,3-Diphenylcyclopropane-1-
carboxylic acid was synthesized following literature proce-
2
6
dures and converted to the ester or amide derivatives by
coupling with the corresponding alcohol or amine using 1,3-
dicyclohexylcarbodiimide/4-(dimethylamino)pyridine (DCC/
2
7
DMAP). The products were purified by silica gel column
chromatography using hexanes-ethyl acetate as the eluent.
Spectral data for esters and amides are provided as Supporting
Information.
(
b) Th e Ch ir a l Au xilia r y Ap p r oa ch : Dia ster eoselec-
t ivit y. Compound 1g (2-3 mg) was dissolved in 0.5 mL of
dichloromethane followed by the addition of 15 mL of hexanes.
+
+
+
+
+
MY (M ) Li , Na , K , Rb and Cs ) zeolite (300 mg) activated
Mea su r em en t of P h otosta tion a r y-Sta te Com p osition .
at 500 °C was added with stirring. The slurry was stirred for
4
′-Methoxyacetophenone (20-25 mg) and compound 1a -e
1
2 h, filtered, and washed thoroughly with fresh hexanes
(
3-4 mg) were dissolved in 0.5 mL of dichloromethane followed
(
analysis of the supernatant showed absence of the reactant).
+
+
+
by the addition of 15 mL of hexanes. MY (M ) Li , Na , K ,
-3
The zeolite was dried under vacuum (2 × 10 Torr) at 60 °C
for 6-8 h. The sample was transferred into a quartz test tube
inside a drybox, fresh anhydrous hexanes was added, and the
test tube was stoppered with a rubber septum and wrapped
with Parafilm. The slurry was then irradiated (unfiltered
output from a 450 W medium pressure mercury lamp), filtered,
and washed again with fresh hexanes (analysis of the super-
natant showed absence of reactants and products). The
reactant and the photoproducts were extracted from the zeolite
by stirring with acetonitrile. The extract was concentrated and
analyzed on GC. The authentic samples (photoproducts inde-
pendently synthesized) were injected in the GC/HPLC and
verified with the retention times of the photoproducts.
GC/HP LC An a lysis Con d ition s. n-Butylamide of 2â,3â-
diphenylcyclopropane-1R-carboxylic acid (1b): Chiralpak-AD;
hexane/2-propanol ) 90:10; flow ) 0.4 mL/min; HP-5890 series
II gas chromatograph; SE-30 column.
+
+
Rb , and Cs ) zeolite (300 mg) activated at 500 °C was added
with stirring. The slurry was stirred for 12 h on a water bath
at 55 °C, filtered, and washed thoroughly with fresh hexanes
(
supernatant was analyzed for the absence of the reactant and
-
3
the sensitizer). The zeolite was dried under vacuum (2 × 10
Torr) at 60 °C for 6-8 h. The sample was transferred into a
test tube inside a drybox, fresh anhydrous hexanes was added,
and the test tube was stoppered with a rubber septum and
wrapped with Parafilm. The slurry was degassed with N
2
for
3
0 min, irradiated (unfiltered output from a 450 W medium-
2
pressure mercury lamp) under positive N pressure, filtered,
and washed again with fresh hexanes (analysis of the super-
natant showed the absence of reactant and products). The
reactant and the photoproducts were extracted from the zeolite
by stirring with acetonitrile. The extract was concentrated and
analyzed on GC. The photostationary state was attained in
all cases within 48 h. They were tested to be true photosta-
tionary states by continuing the irradiation for further 48 h.
The extraction was carried out using dichloromethane or
Benzylamide of 2â,3â-diphenylcyclopropane-1R-carboxylic
acid (1c): Chiralpak-AD; hexane/2-propanol ) 85:15; flow )
0
.5 mL/min; HP-5890 series II gas chromatograph; SE-30
column.
(
25) (a) Fukuzumi, S.; Itoh, S. Adv. Photochem. 1999, 25, 107. (b)
3
-Phenylethylamide of 2â,3â-diphenylcyclopropane-1R-car-
Fukuzumi, S. Bull. Chem. Soc. J pn. 1997, 70, 1. (c) Fukuzumi, S.; Fujii,
Y.; Suenobu, T. J . Am. Chem. Soc. 2001, 23, 1019. (d) Fukuzumi, S.;
Mori, H.; Imahori, H.; Suenobu, T.; Araki, Y.; Ito, O.; Kadish, K. M. J .
Am. Chem. Soc. 2001, 123, 12458. (e) Fukuzumi, S.; Satoh, N.;
Okamoto, T.; Yasui, K.; Suenobu, T.; Seko, Y.; Fujitsuka, M.; Ito, O.
J . Am. Chem. Soc. 2001, 123, 7756. (f) Itoh, S.; Kumei, H.; Nagatomo,
S.; Kitagawa, T.; Fukuzumi, S. J . Am. Chem. Soc. 2001, 123, 2165.
boxylic acid (1d ): Chiralpak-AD-RH; hexane/2-propanol ) 95:
05; flow ) 0.5 mL/min; HP-5890 series II gas chromatograph;
SE-30 Column.
Methyl ester of 2â,3â-diphenylcyclopropane-1R-carboxylic
acid (1e): Shimadzu 17-A gas chromatograph; SE-30 column.
Ethyl ester of 2â,3â-diphenylcyclopropane-1R-carboxylic acid
(1f): HP-5980 series II gas chromatograph; column â-dex-350/
OV170; Shimadzu 17-A gas chromatograph; SE-30 column.
(
26) (a) Orchin, M.; Blatchford, J . K. J . Org. Chem. 1964, 29, 839.
b) D’yakanov, I. A.; Komendantev, M. I.; Gui-siya, F.; Korichev, G. L.
J . Gen. Chem. USSR 1962, 32, 928. (c) 2â,3â-Diphenylcyclopropane-
(
1
R-carboxylic acid was synthesized by using cis-stilbene, and rac-2,3-
diphenylcyclopropane-1-carboxylic acid was synthesized using trans-
stilbene.
(
-) Menthyl ester of 2â,3â-diphenylcyclopropane-1R-car-
boxylic acid (1g): HP-5890 series II gas chromatograph; HP-5
(27) Hassner, A.; Alexanian, V. Tetrahedron Lett. 1978, 46, 4475.
column.
J . Org. Chem, Vol. 67, No. 25, 2002 8719

Kaanumalle et al.
Com p u ta tion a l Meth od s Used . Full geometry optimiza-
tions were carried out primarily using the hybrid Hartree-
Fock density functional theory (RB3LYP) with Becke three-
parameter exchange functional in conjunction with correlation
functional by Lee, Yang, and Parr (LYP). The 6-31G* basis
set was used for C, H, O, N, Li, Na, and K. Stationary points
have been characterized as true minima by frequency calcula-
tions. Binding affinities were computed using the “super
system” approach without inclusion of basis set superposition
error corrections. All the calculations were performed using
Gaussian 98 A.6 suite of quantum chemical programs.
financial support and Tulane Computing Center (sup-
ported by the Department of Energy) for generous use
of their facility. R.B.S. thanks CSIR (New Delhi) for a
research fellowship.
Su p p or tin g In for m a tion Ava ila ble: Spectral data for the
cis and trans isomers of derivatives of 1,2-diphenylcyclopro-
pane and 2â,3â-diphenylcyclopropane-1R-carboxylic acid 1 and
2 and Cartesian coordinates of all computed structures. This
material is available free of charge via the Internet at
http://pubs.acs.org.
Ack n ow led gm en t. V.R. thanks the National Sci-
ence Foundation (CHE-9904187 and CHE-0212042) for
J O026137K
8
720 J . Org. Chem., Vol. 67, No. 25, 2002