Photochemistry in a crystalline cage. Control of the Type-B bicyclic reaction course: Mechanistic and exploratory organic photochemistry

Article abstract of DOI:10.1021/ja9630396

Our current theories on crystal lattice control of organic photochemistry were subjected to studies of type-B rearrangement of bicyclo[3.1.0]hex-3-en-2-ones. A first finding was that the solid state photochemistry differed dramatically from that in solution. One of our past observations in this bicyclic photochemistry in solution was that the six-membered ring, type B, zwitterion was a ubiquitous intermediate. This intermediate invariably underwent a preferential migration of an aryl group to carbon-2 relative to carbon-4 with formation of a 2,3-disubstituted phenol, a result deriving from electronic effects. In contrast, the crystal lattice photochemistry revealed a regioselectivity depending on the surrounding lattice rather than electronics. Perhaps an even more dramatic difference was an observation of the dependence of reactant stereochemistry. Thus, in solution, for 6,6-disubstituted bicyclics with two different groups at C-6, a common zwitterion is formed and the same photoproduct is formed independent of reactant stereochemistry. In crystal lattices the endo and exo stereoisomers of the 6,6-disubstituted bicyclics react differently and the group originally endo tends to migrate after three-ring opening to the zwitterion. The experimental results were paralleled with a theoretical analysis. This consisted of generation of a 'mini crystal lattice' with sufficient lattice molecules to completely surround a central, reacting electronically excited state molecule. Then computational extraction of the central molecule and replacement by a transition structure afford a model of the reacting excited state inside the crystal lattice. Overlap of this species with the lattice neighbors and energy computations are then possible. These permit prediction and understanding of excited state crystal lattice reactivity on a quantitative basis.

Full text of DOI:10.1021/ja9630396

J. Am. Chem. Soc. 1997, 119, 3677-3690
3677
Photochemistry in a Crystalline Cage. Control of the Type-B
Bicyclic Reaction Course: Mechanistic and Exploratory
Organic Photochemistry1,2
Howard E. Zimmerman* and Pavel Sebek
Contribution from the Chemistry Department, UniVersity of Wisconsin,
Madison, Wisconsin 53706
ReceiVed August 28, 1996X
Abstract: Our current theories on crystal lattice control of organic photochemistry were subjected to studies of
type-B rearrangement of bicyclo[3.1.0]hex-3-en-2-ones. A first finding was that the solid state photochemistry differed
dramatically from that in solution. One of our past observations in this bicyclic photochemistry in solution was that
the six-membered ring, type B, zwitterion was a ubiquitous intermediate. This intermediate invariably underwent a
preferential migration of an aryl group to carbon-2 relative to carbon-4 with formation of a 2,3-disubstituted phenol,
a result deriving from electronic effects. In contrast, the crystal lattice photochemistry revealed a regioselectivity
depending on the surrounding lattice rather than electronics. Perhaps an even more dramatic difference was an
observation of the dependence of reactant stereochemistry. Thus, in solution, for 6,6-disubstituted bicyclics with
two different groups at C-6, a common zwitterion is formed and the same photoproduct is formed independent of
reactant stereochemistry. In crystal lattices the endo and exo stereoisomers of the 6,6-disubstituted bicyclics react
differently and the group originally endo tends to migrate after three-ring opening to the zwitterion. The experimental
results were paralleled with a theoretical analysis. This consisted of generation of a “mini crystal lattice” with
sufficient lattice molecules to completely surround a central, reacting electronically excited state molecule. Then
computational extraction of the central molecule and replacement by a transition structure afford a model of the
reacting excited state inside the crystal lattice. Overlap of this species with the lattice neighbors and energy
computations are then possible. These permit prediction and understanding of excited state crystal lattice reactivity
on a quantitative basis.
Introduction
Scheme 1. Type-B Rearrangement via a Zwitterion
Intermediate4e a
One of the most fascinating reactions we have encountered
in our photochemical studies has been the type-B3 rearrangement
of bicyclo[3.1.0]hex-3-en-2-ones.4 The reaction of the n-π*
triplet permits two competitive three-membered ring openings.
A priori, either the internal bond or an external bond might be
severed. Irreversible fission of the internal bond leads to a six-
membered ring diradical as shown in Scheme 1. Intersystem
crossing affords the type-B zwitterion which then rearranges.4
In our previous studies, we have investigated a variety of
complex rearrangements which proceed differently in crystalline
media than in our earlier solution research. More importantly,
we provided a new general theory correlating reactivity with
crystal structure.5,6 Thus, we decided to extend our efforts to
the type-B bicyclic rearrangement. The basic philosopy is that,
a 2T is a triplet while 2S0 is a ground state singlet.
X Abstract published in AdVance ACS Abstracts, March 15, 1997.
(1) This is paper 245 of our general series and 180 of our photochemical
papers.
(2) For our last photochemical publication see: Zimmerman, H. E.;
Hoffacker, K. D. J. Org. Chem. 1996, 61, 6526-6534.
(3) This rearrangement originally was termed a “type B” process as it
was the reaction of the product of the “type A” lumi rearrangement.
However, the migration of a π-group from C-4 to C-3 of the cyclohexenone
also has been termed a type B process. Thus, “type-B bicyclic” and “type-B
enone” are more appropriate.
even with minor changes in substituents, not anticipated to have
major effects on solution photochemistry, one may expect
different crystal packing patterns and different space groups.
With different orientations of neighboring molecules in a crystal,
any one reacting excited state molecule should have its reactivity
modified in a major way by the surrounding lattice.
Results
(4) (a) Zimmerman, H. E.; Schuster, D. I. J. Am. Chem. Soc. 1961, 83,
4486-4487. (b) Zimmerman, H. E.; Schuster, D. I. J. Am. Chem. Soc.
1962, 84, 4527-4540. (c) Zimmerman, H. E.; Grunewald, J. O. J. Am.
Chem. Soc. 1967, 89, 3354-3356. (d) Zimmerman, H. E.; Grunewald, J.
O. J. Am. Chem. Soc. 1967, 89, 5163-5172. (e) Zimmerman, H. E.; Epling,
G. A. J. Am. Chem. Soc. 1972, 94, 3245-3246. (f) Zimmerman, H. E.;
Epling, G. A. J. Am. Chem. Soc. 1972, 94, 7806-7811. (g) The “circle-
dot-y” notation was introduced4a,b to permit one to write a three-dimensional
electronic structure in two dimensions. The o’s represent sp hybrid
electrons, py’s the “n” in-plane electrons, solid dots π-system electrons,
and double bonds π-system electron pairs.
Synthesis of Reactants. The syntheses of starting materials
are outlined in Schemes 2-4. One basic approach involved
the thermal reaction of diaryldiazomethanes with cyclopent-2-
(5) (a) Zimmerman, H. E.; Zuraw, M. J. J. Am. Chem. Soc. 1989, 111,
2358-2361. (b) Zimmerman, H. E.; Zuraw, M. J. J. Am. Chem. Soc. 1989,
111, 7974-7989.
(6) (a) Zimmerman, H. E.; Zhu, Z. J. Am. Chem. Soc. 1994, 116, 9757-
9758. (b) Zimmerman, H. E.; Zhu, Z. J. Am. Chem. Soc. 1995, 117, 5245-
5262.
S0002-7863(96)03039-9 CCC: $14.00 © 1997 American Chemical Society

3678 J. Am. Chem. Soc., Vol. 119, No. 16, 1997
Scheme 2. Synthesis of Diphenyl Reactants
Zimmerman and Sebek
Scheme 5. Synthesis of Some 5-Substituted
3,4-Diphenylphenols
Scheme 6. Synthesis of Two Linearly Conjugated Dienones
Scheme 3. Synthesis of Stereoisomeric Reactants
Scheme 7. Synthesis of 3-Phenyl-4-(p-Cyanophenyl)phenol
Scheme 4. Synthesis of Phenyl, p-Cyanophenyl Reactants
substituted â-carbon and then onward to C-2. For this reason
the alternative synthesis starting from methoxy diphenyl enone
14 was employed; it did afford the product anticipated from a
simple dienone-phenol rearrangement.
ene-1,4-dione to afford a bicyclo[3.1.0]hex-3-en-2-one skeleton.
This general approach has proven useful in our earlier research.7
Presently, the methodology, in leading to the enol ethers of
bicyclo[3.1.0]hexane-1,3-diones, had the advantage of permitting
the facile introduction of a variety of groups at the â-carbon of
the enone moiety. As noted above, such minor variation in
structure promised totally different solid-state photochemistry
in these closely related reactants.
Synthesis of Potential Photoproducts. In addition, with
known solution photochemistry in mind and with mechanistic
reasoning, some potential photoproducts were selected for
independent synthesis. The selection was based as well on
structures of photoproducts encountered in the research as it
proceeded. We concentrated our synthesis on photoproducts
which promised to be elusive and less available for structure
elucidation. Independent synthesis of really major photoprod-
ucts was less necessary, since these compounds were readily
available for X-ray structure determination.
From our previous investigations there was reason to antici-
pate the formation of both 2,3-diphenyl-substituted and 3,4-
diphenyl-substituted phenols. However, in the present study,
of course, additional groups were present. Additionally, there
was evidence for the role of linearly conjugated cyclohexa-2,4-
dienones, and three were synthesized as well. These syntheses
are outlined in Schemes 5-7.
The dienone-phenol rearrangement of 12b and 12d to give
the 5-methyl- and 5-tert-butyl-3,4-diphenylphenols (13b and
13d) (note Scheme 5), respectively, is not totally unambiguous,
since there is the possibility of the C-4 phenyl migrating to the
In the case of the dienone-phenol rearrangement of 4-phenyl-
4-(p-cyanophenyl)cyclohexa-2,5-dienone (18), the product struc-
ture 19 is deduced from the preference for phenyl over
p-cyanophenyl migration in cationic rearrangements.
Photochemistry. Solution Behavior. For our study of the
effect of crystal lattices on the photochemistry of these bicyclic
systems, it was necessary first to determine the behavior in
solution. Irradiation in benzene led to three types of photo-
products: (a) substituted phenols, (b) ketenes and their products
of nucleophilic addition, and (c) 2,4-cyclohexadienones (i.e.,
“linear dienones”). From a different perspective, mechanistic
in nature, there are several alternative bond-fission processes
which are potentially available to the excited state. One is
scission of the internal three-ring bond. A second is breaking
of an out-of-plane bond. Since here we are concerned with the
nature of the products, the mechanistic aspects will be mentioned
here only when relevant and delayed for the Discussion of
Results section.
Thus, the solution photochemistry was carried out first.
Scheme 8 tabulates the course of the reactions and the products
obtained. The photoproduct structures in the cases of 20a and
20c were known, independently prepared and checked by NMR
analysis. Of the remaining structures, 16a, 16c, and 16d were
synthesized independently and the structures of 16b, 20d, 20e,
and 21 were established by X-ray analysis. The structure of
20b was derived from NMR analysis (see the Experimental
Section).
We note that in Scheme 8 both the 2,3-diphenylphenol
derivatives and the linearly conjugated 2,4-cyclohexadienone
(7) Zimmerman, H. E.; Pasteris, R. J. J. Org. Chem. 1980, 45, 4864-
4876.

Photochemistry in a Crystalline Cage
J. Am. Chem. Soc., Vol. 119, No. 16, 1997 3679
Scheme 8. Solution Photolysis of a Series of Bicyclics
Scheme 10. Photolysis of p-Bromophenyl, Phenyl Bicyclics
in Benzene
a Ratios by NMR analysis.b Maximum conversion studied without
variation.
Scheme 11. Crystal Lattice Photolysis of a Series of
Bicyclics
Scheme 9. Irradiation of the Stereoisomeric p-Cyanophenyl,
Phenyl Bicyclics in Benzene
a Loss of selectivity beyond 15%.b Melting beyond 70% conver-
sion.c Not attempted beyond 30%.d Loss of selectivity and new
products beyond 5% conversion.
derivatives 16 are formed in every case. However, with a
diphenylmethoxy substituent, a new photoproduct, 21, an
unsaturated ketone, is formed.
solvents, the photoacid of structure Ar2CdCHsCHdCHsCH2s
COOH was formed instead.
Finally, irradiation of each cyanophenyl bicyclic (i.e., 7e or
7f) with partial conversion to photoproduct resulted in no
interconversion of the reactant with its stereoisomer.
A similar photolysis of the p-bromophenyl, phenyl bicyclics
24a and 24b (Scheme 10) differed in proceeding with nearly
equal extents of phenyl-migrated and bromophenyl-migrated
phenols (i.e., 26 and 27). However, the product ratio was again
found to be independent of reactant configuration.
While we defer discussion of the detailed reaction mecha-
nisms, for the present we note differences from our earlier
solution studies4,7-9 in polar solvents. Thus, in contrast, no 3,4-
diarylphenols are formed from irradiation in benzene. In polar
media the linear cyclohexadienones were not formed.
Also, products resulting from a conjugated ketene (Ph2Cd
CHsCHdCHsCHdCdO) were encountered in nucleophilic
solvents but not presently in benzene. Finally, the formation
of the unsaturated ketone 21 is without precedent.
The solution photochemistry of the stereoisomeric 6-(p-
cyanophenyl)-6-phenylbicyclo[3.1.0]hexenones 7e and 7f was
of considerable interest not only for comparison with the solid-
state chemistry but also because in our earlier studies4c,d in polar
solvents it had been observed that there was complete regiose-
lectivity with preferential migration of phenyl relative to
p-cyanophenyl. Additionally, there was a preference for migra-
tion to carbon-2 compared to C-4 in a ratio of 3:1. This evi-
dence indicated that the intermediate undergoing aryl migration
was the zwitterion 2S0 rather than its triplet counterpart 2T (note
Scheme 1). The reasoning was that, in migrations to an odd-
electron center, cyanophenyl should be preferred while in migra-
tions to a cationic center, phenyl should migrate more readily.
In benzene solvent, the same preference for phenyl migration
was observed. However, in contrast to the polar solvent
irradiation, independent of reactant stereochemistry, only migra-
tion to carbon-2 resulted; note Scheme 9. In this case the
2-phenyl-3-(p-cyanophenyl)phenol (23) was known from our
earlier studies4c,d and the structure of the linear dienone 22 was
established by its NMR spectrum and its spectroscopic pattern
close to that of the other linear dienones. Note Scheme 9 for
the reaction course observed in benzene.
Photochemistry. Crystal Lattice Behavior. In pursuing
the crystal lattice counterparts of the solution photochemistry,
we began by studying the â-substituted bicyclics (i.e., 5a, 5b,
5c, 5d, and 5e). The photochemical methodology utilized was
patterned after that which we used in our earlier studies. The
results with reactants 5a, 5b, 5c, and 5d are collected in Scheme
11. The results obtained from 5e are discussed separately.
Evidence for those photoproducts also formed in the solution
photochemistry has been discussed above. The structure of 3,4-
diphenylphenol (13a) was known.4a,b That of 5-methyl-2,3-
diphenylphenol (13b) and 5-tert-butyl-2,3-diphenylphenol (13d)
was derived from independent syntheses discussed earlier.
Similarly 3-tert-butyl-6,6-diphenyl-1,3-cyclohexadienone (16d)
had been independently prepared (vide supra).
The case of the â-benzhydroxy bicyclic 5e proceeded
differently in that no phenolic photoproducts resulted. In
addition, the NMR spectrum of the crystalline photoproduct
showed a (diphenylmethoxy)ketene, 37e, to be the main
product. However, after photolysis, dissolving in THF-water
the diphenylmethoxy carboxylic acid 28 was formed along with
the methyl ketone 21 (Scheme 12). On keeping the photolysis
product in dry benzene for 1.5 h or, instead, melting the crystal,
the linear dienone 16e was obtained along with the same methyl
ketone 21. Thus, the crystal lattice photolysis contrasted with
the solution photochemistry in affording none of the phenol 20e
but was similar in giving the linear dienone 16e seen in the
solution photochemistry.
The second difference in this benzene photolysis was the
formation of the linear dienone 22. In aqueous nucleophilic
(8) Zimmerman, H. E.; Nasielski, J.; Keese, R.; Swenton, J. S. J. Am.
Chem. Soc. 1966, 88, 4895-4903.
(9) Zimmerman, H. E.; Lynch, D. C. J. Am. Chem. Soc. 1985, 107, 7745-
7756.
Turning to the stereoisomeric 6-(p-cyanophenyl)-6-phen-
ylbicyclo[3.1.0]hex-3-en-2-ones, 7e and 7f, crystal lattice

3680 J. Am. Chem. Soc., Vol. 119, No. 16, 1997
Zimmerman and Sebek
Scheme 12. Crystal Photochemistry of the
Diphenylmethoxy Bicyclic 5e
Figure 1. Two alternative pathways for the type-B zwitterion.
Scheme 15. Ketene Formation and Competitive Reactionsa
Scheme 13. Crystal Lattice Photolysis of the
p-Cyanophenyl, Phenyl Bicyclics
a 5T and 36 are triplets.
Interpretative Discussion
Discussion of the Solution Photochemistry. The preference
for the formation of 2,3-diphenylphenols relative to the their
3,4-isomers has been ascribed to lower energy of the bridged
zwitterionic species 34 compared with 35.4b,8,10 This is the spe-
cies leading from the type-B zwitterion4,8 2So in Scheme 1 on-
ward to the two alternative phenols. The selectivity results from
extra delocalization of the dienolate 34 compared to the mono-
enolate 35. This is the qualitative suggestion we made decades
ago. AM1 and ab initio computations now confirm this; an
energy difference (AM1, 17.3 kcal/mol; G92 CASSCF(2,2)/3-
21G, 13.2 kcal/mol) (see Figure 1) favors the 2,3-zwitterion.
As noted above, the selectivities tended to be on the order of
3:1. As the acidity of the medium was increased, migration to
C-4 increased relative to C-2.8 In contrast, however, in benzene
only the 2,3-diphenyl isomer was formed. Since this was
observed for all cases studied, it appears to be a general
phenomenon. The most reasonable rationale seems to be that,
in hydroxylic solvents, the negative oxygen becomes hydrogen
bonded with inhibition of enolate delocalization, the source of
the regioselectivity preferring migration to C-2 (vide supra).
This also accounts for the lower selectivity in hydrogen bonding
solvents than anticipated from a 13 kcal/mol calculated energy
difference.
Scheme 14. Crystal Lattice Photochemistry of the
p-Bromophenyl, Phenyl Bicyclics
conversions were carried out in runs ranging up to 20% in the
case of 7e and 40% in the case of 7f. This chemistry is outlined
in Scheme 13. Unlike the solution photochemistry, the reaction
course did depend on the configuration of the reactant bicyclic
enone. In the case of the exo-cyano stereoisomer 7f, the normal
preference for phenyl vs cyanophenyl migration was observed.
Additionally, the usual preference for migration to C-2 compared
to C-4 was seen. In dramatic contrast, the endo reactant 7e led
to a preference for cyanophenyl migration, both to C-2 and to
C-4, with the former being preferred. Thus, it is the endo group
which tends to migrate predominately.
The stereoisomeric 6-(p-bromophenyl)-6-phenylbicyclo[3.1.0]-
hex-3-en-2-ones 24a and 24b were the last to be studied as
crystal lattices. The results are given in Scheme 14. In the
case of the exo stereoisomer 24a a 3:1 preference for phenyl
migration to C-2 compared with C-4 was encountered; only a
minor amount (ca. 3 %) of bromophenyl migration was
observed. The endo stereoisomer 24b, in contrast, afforded
bromophenyl migration with the phenyl migration product (i.e.,
26) as a very minor product. Thus, again these results are quite
different from those of the solution photochemical counterpart.
Firstly, here in the crystal lattice photochemistry, the same
product distribution did not result from the two stereoisomers.
Secondly, the linear dienone 25 was not formed. Thirdly, the
preference for phenyl migration no longer was encountered. And
finally, there was a preference for the endo group to migrate.
A second point of interest is the formation of the linear
dienones11a-c which had not been observed in our earlier solution
photochemistry carried out in hydroxylic solvents. While the
phenolic photoproducts result from in-plane three-ring fission,
the formation of ketenes results from external three-ring bond
breaking as outlined in the mechanism in Scheme 15. In the
presence of a nucleophile, an acid or acid derivative is formed
by trapping4 while in the absence of a nucleophile, as in benzene
solvent, an electrocyclic closure to form linear dienone occurs.
(10) Zimmerman, H. E. In AdVances in Photochemistry; Noyes, A., Jr.,
Hammond, G. S., Pitts, J. N., Jr., Eds.; Interscience: New York, 1963;
Vol. 1, pp 183-208.
(11) (a) See refs 11b,c for examples and further references on the thermal
cyclization of ketones to linear cyclohexadienones. For a discussion see:
Schaffner, K. In Rearrangements in Ground and Excited States; DeMayo,
P., Ed.; Academic Press: New York, 1980; pp 328-330. (b) Quinkert, G.
Angew. Chem. 1972, 11, 1072-1087. (c) Chapman, O. L.; Kane, M.;
Lassila, J. D.; Loeschen, R. L.; Wright, H. E. J. Am. Chem. Soc. 1969, 91,
6856-6858. (d) Allinger, N. L. MM3; University of Georgia, December
1990. (e) Dewar, M. J. S.; Zoebisch, E. G.; Healy, E. F.; Stewart, J. J. P.
J. Am. Chem. Soc. 1985, 107, 3902-3909.

Photochemistry in a Crystalline Cage
J. Am. Chem. Soc., Vol. 119, No. 16, 1997 3681
Scheme 16. Mechanism Involving Secondary Photolysis of
the Ketene
to the solution photochemistry, fission of the internal three-
ring bond did not lead to a common intermediate with common
behavior. What is meant here is that the intermediate zwitterion
must be taken as paired with the surrounding lattice which
differs for the two reactants. Thus, it was observed that the
aryl group which was originally endo was the one which
migrates. Qualitatively, this may be understood on the basis
that the endo group is “tucked” into a space within the
molecule’s outer periphery rather than protruding into the lattice
space. The endo group hence has more possibility for motion.
This is not obvious and emphasizes the importance of quantita-
tive assessment of lattice interference. Preferential migration
of the p-cyanophenyl group in the case of the endo reactant
provides an antithesis to solution mechanistic considerations.
A priori, either (i) an electronically reluctant cyanophenyl group
is forced to migrate to a somewhat positive center in the type-B
zwitterion or, alternatively, (ii) rearrangement of the precursor
triplet diradical (of general structure 2T in Scheme 1) is more
rapid than intersystem crossing, and it is the triplet diradical
which rearranges in the crystal. In migration of a triplet
diradical such as 2T, cyanophenyl migration should take
preference over phenyl migration. It is possible that steric
constraints might prevent formation of a conformation favorable
to optimal spin-orbit coupling with consequent inhibition of
intersystem crossing. But since the endo group is the less
hindered one, this possibility seems remote. Hence, aryl
migration of the zwitterion seems the more likely mechanism.
The preference for migration of the endo-aryl group is
confirmed by the same behavior of the p-bromophenyl, phenyl-
substituted bicyclics 24a and 24b where a totally different lattice
is present. Another difference observed for the cyanophenyl
and bromophenyl reactants is lack of external three-ring fission,
leading to a linear dienone and hence a ketene. Intuitively it
seems that scission of an out-of-plane bond requires more space
than fission of an in-plane bond. Finally, that appreciable
migration of aryl groups to C-4 occurred, contrasting with the
reactivity in benzene, is only part of the pattern of the a priori
unpredictability of crystal lattice behavior.
Quantitative Treatments. We have reported several quan-
titative treatments of crystal lattice reactivity.5,6 The basic
approach involves computer generation of a “mini crystal lattice”
composed of just enough molecules (e.g., 20) to completely
surround a central molecule which is then taken as the reacting
one. Next, this central molecule is computationally removed
from the crystal lattice and replaced by a variety of alternative
transition structure models. The most useful structures for the
purpose of predicting a reaction course are the “branch points”,
namely, the alternative species formed from a common precursor
which has partitioned itself. Thus, for 2,3-aryl migration relative
to 3,4-aryl migration, structures 34 and 35 were used with
appropriate substitution and with stereochemistry corresponding
to that of its precursor. The electronic state was not defined.
One way of considering this situation is expressed in eqs 1a
and 1b. Here we have the energies of the components of the
crystal lattice with the included central molecule. This central
Scheme 17. Alternative Mechanism for Formation of
Methyl Ketone
A final point about the competition between the in-plane
versus out-of-plane bond scission is that overlap of the π-system
with the in-plane bond is not orthogonal as might be surmised.
Thus, the Coulson “banana” bonds are close to sp5 oriented and
aim below the five-membered ring.
One particularly interesting case is the photolysis of the
â-(diphenylmethoxy)-6,6-diphenylbicyclo[3.1.0]hex-3-en-2-
one (5e) to afford the methyl ketone 21 in addition to the 2,3-
diphenylphenol 20e and the linear dienone 16e. Two mecha-
nisms are reasonable possibilities; note Schemes 16 and 17.
The second possible mechanism assumes that the enediol
intermediate, formed in the reaction of the ketene, rearranges
in a thermal process as depicted in Scheme 17. The driving
force for this process is conversion of the unstable enediol to a
more stabilized enol of a â-dicarbonyl compound.
Discussion of the Crystal Lattice Photochemistry. The
Differences. That the photochemistry observed in crystal
lattices differed from the solution counterparts was not surpris-
ing, and the differences emphasize the way in which external
steric constraints, imposed by the surrounding lattice, may
overcome the normal electronic and other intramolecular
energetic factors which control a solution reaction. The
variations with different lattice constraints, however, are
dramatic and informative.
One of the striking results was the observation that the normal
preference for formation of the 2,3-diphenylphenols character-
istic of the solution photochemistry was no longer general. In
the parent bicyclic 5a, lacking substituents, close to equal
amounts of the 2,3-diphenyl- and 3,4-diphenylphenols were
found. With a â-methyl substituent, the bicyclic 5b gave only
migration to carbon-4. Thus, the 13 kcal/mol electronic
preference (vide supra) was overcome by the crystal lattice cage
effect.
Another remarkable difference was the absence of formation
of the ketenes and the ketene cyclization products, namely, the
linear dienones, in three of the bicyclics studied (i.e., 5a, 5b,
and 5c).
In the case of the diphenylmethoxy bicyclic 5e the ketene
photoproduct, along with the methyl ketone 21, could be
observed at the reaction end, thus permitting observation of the
reactivity of the ketene.
A particularly remarkable result was found in the p-cy-
anophenyl, phenyl-substituted bicyclics 7e and 7f. In contrast
molecule might be the reactant (eq 1a) or an imbedded transition

3682 J. Am. Chem. Soc., Vol. 119, No. 16, 1997
Table 1. Calculated Deformation and Interaction Energies (kcal/mol) for the Branch Points for Phenol Formation with Rigid Superpositions
migration to C-2 migration to C-4
Zimmerman and Sebek
substrate
obsd
Ed
Ei
sumd
obsd
Ed
Ei
sumd
H endo
H exo
Me endo
Me exo
MeO endo
MeO exo
t-Bu endo
t-Bu exo
CNPh endo
Ph exo
c
12.7
18.4
21.6
16.0
3.2
17.9
8.8
14.7
10.6
39.9
-37.1
-34.0
-30.1
-27.8
-34.8
-30.8
-51.8
-48.1
-41.2
-22.5
-24.4
-15.6
-8.5
-11.8
-31.6
-12.9
-43.0
-33.4
-30.6
17.4
c
10.7
19.1
10.7
13.5
15.0
17.0
8.5
15.3
10.8
19.4
-33.7
-21.4
-32.1
-18.7
-24.7
-25.1
-37.3
-32.7
-38.0
36.9
-23.0
-2.3
c
-21.9
-5.2
c
c
c
-9.7
-8.1
-28.8e
-17.4
-27.2e
17.5
Ph endo
CNPh exo
BrPh endo
Ph exo
X-ray data not available
c
c
9.2
26.5
13.0
17.7
12.8
26.2
-39.0
-26.2
-42.8
-24.9
-34.6
-30.3
-29.8
30.7
19.9
14.0
16.1
12.3
20.6
6.1
-32.6
-39.6
-28.5
-39.7
-30.7
36.8
-12.7
-25.6
-12.4
-27.4
-10.1
0.3
Pha endo
BrPh exo
Phb endo
BrPh exo
-29.8
c
-7.2
-21.8
-4.1
a Molecule 1. b Molecule 2. a and b refer to two conformations in the crystal lattice. c Process predicted and in accord with observation.
d Underlining indicates observed products. e Minor product.
Table 2. Calculated Deformation and Interaction Energies (kcal/mol) for the Branch Points for Phenol Formation with Flexible Superpositions
migration to C-2
migration to C-4
substrate
obsd
Ed
Ei
sumd
obsd
Ed
Ei
sumd
H endo
H exo
Me endo
Me exo
MeO endo
MeO exo
t-Bu endo
t-Bu exo
CNPh endo
Ph exo
c
11.8
9.1
21.2
15.0
3.7
16.0
9.7
14.5
11.5
28.4
-37.0
-33.8
-30.0
-28.1
-35.3
-29.9
-51.8
-47.9
-41.5
-26.7
-25.2
-14.7
-8.8
-13.1
-31.6
-13.9
-42.1
-33.4
-30.0
1.7
c
11.1
19.1
9.5
14.3
14.1
19.5
9.6
19.4
10.8
20.2
-33.3
-22.0
-31.8
-19.7
-25.2
-27.2
-38.7
-36.4
-37.2
-37.6
-22.2
-2.9
c
-22.3
-5.4
c
c
c
-11.1
-7.7
-29.1e
-17.0
-26.2e
17.4
Ph endo
CNPh exo
BrPh endo
Ph exo
X-ray data not available
c
c
8.9
29.7
12.1
20.6
12.3
26.9
-39.6
-28.9
-38.8
-33.3
-34.5
-31.1
-30.7
27.7
18.5
11.7
16.1
10.4
20.0
-36.0
-32.8
-38.0
-28.5
-39.0
-29.3
-8.3
-14.3
-26.3
-12.4
-28.6
-9.3
0.8
Pha endo
BrPh exo
Phb endo
BrPh exo
-26.7
-12.7
-22.2
-4.2
c
a For conformer I in the crystal lattice. b For conformer II in the crystal lattice. c See footnote c in Table 1. d See footnote d in Table 1. e See
footnote e in Table 1.
structure, intermediate, or product (eq 1b). EL is the summation
of the energy of the empty lattice, plus the energy of the guest
(i.e., ER or ES), as it exists in the lattice, plus the energy of
interaction of the guest with the lattice (i.e., ELR or ELS).
However, since the imbedded guest molecule will be deformed
somewhat by inclusion in the lattice, its energy can be further
dissected into its optimal energy when isolated outside the lattice
plus a deformation energy. All of this is summarized in eqs 1a
and 1b.
EL for the mini crystal lattice is measurable using molecular
mechanics. After computational extraction of the central,
imbedded molecule, EL(empty) is measurable in the same way.
The third item calculated is ES (or ER) in eq 1, namely, the
energy of the extracted molecule in the conformation it originally
had in the crystal. Thus, all terms of either eq 1a or eq 1b are
known except for one, ELS or ELR, which is the lattice-guest
interaction energy. This is obtained then by difference.
Geometry optimization of the extracted molecule leads to a
lowering of its energy, since it had been deformed by the
surrounding lattice molecules. The energy decrease on geometry
optimization then corresponds to the molecule’s deformation
energy, the penalty it pays for inclusion in the lattice.
Finally, the subtraction of corresponding terms in eq 1a from
eq 1b, we can determine the total energy change ∆EL in having
the new molecule in the crystal lattice compared with the
reactant. Alternatively, one can determine the guest deformation
energy and the energy due to lattice-guest interaction. In
placing various molecular species into the mini crystal lattice,
we have used a “rigid superposition”, wherein the molecule with
original geometry is placed so that its atoms are optimally close
to the positions of the original, central lattice molecule replaced.
Here the injected molecule was subjected to geometry optimiza-
tion in the crystal cavity, and its deformation energy (Ed) and
lattice interaction energy (Ei) were calculated. Table 1 gives
results based on this method.
A second approach, “flexible superposition”, permitted dihe-
dral rotation about single non-ring bonds in order to obtain the
optimal position of each atom relative to the atom of reactant
being replaced. Table 2 below gives the energies computed
on this basis. We note that electronic effects are not included
by either method since MM311d was used to compare final
energies.
In our past studies of crystal lattice photochemistry we have
attempted to determine different measures of “fit” of the reacting
molecule in the crystal lattice5,6 including the energetic con-
siderations discussed above. However, still another property

Photochemistry in a Crystalline Cage
J. Am. Chem. Soc., Vol. 119, No. 16, 1997 3683
by Schmidt13b was that such 2π + 2π cycloadditions will take
place when the intermolecular distance between the π bonds is
4.2 Å or less. A particularly interesting approach was described
by Gavezzotti14a who used the packing potential energy of a
dissociating peroxide reactant. This quantity affords the energy
of one molecule taken from infinity and inserted into a crystal
lattice. Another treatment involved molecular volumes available
in cavities of inclusion compounds.14b Still another idea was
the energy of pyramidalization of a dimethylamino group in an
intermolecular methyl transfer reaction, and the packing potential
was also used for this reaction.14c,d Another quantitative
approach, this by Ramamurthy,15 dealt with the dimerization
of coumarin derivatives. The treatment considered local van
der Waals attractive and repulsive forces exerted on the
photoproducts relative to the reactant pairs. A different ap-
proach was employed by McBride16 using molecular mechanics
to ascertain the ease of migration of fragments within the
reaction cavity in free radical dissociations. A recent com-
munication describes the use of molecular mechanics to obtain
the difference in energy of the most stable conformation of a
final product molecule in a crystal lattice and the geometry-
optimized conformation outside of the lattice.17 Scheffer in an
elegant study has compared the ease of two dibenzobarrelene
esters to twist toward a bridged intermediate; in this he used
van der Waals attractive and repulsive forces.18a In a more
recent study he has suggested control by steric compression
effects in a 2 + 2 cycloaddition.18b Ohashi19 has correlated
the volumes of cavities of two crystal modifications with the
rates of racemization of a cobalt complex. Lahav and co-
workers20 have used packing potentials to correlate with ease
of group rotation in considering intermolecular hydrogen
abstraction of deoxycholic acid-acetophenone inclusion com-
pounds. Hasegawa21 studied cinnamate oligomerizations by 2
+ 2 cyclization and correlated these with π-bond separations.
Finally, Thomas22 has used van der Waals attractive and
repulsive forces to obtain potential energies of a molecule with
its adjacent neighbors and related this to 2 + 2 intermolecular
Table 3. Calculated Overlap at the Branch Points for Phenol
Formation with Rigid Superpositions
migration to
migration to
substrate
C-2
C-4
substrate
C-2
C-4
H endo
H exo
Me endo
Me exo
MeO endo
MeO exo
t-Bu endo
t-Bu exo
CNPh endo
Ph exo
*18.8
26.6
31.0
31.9
*10.1
33.1
*12.3
32.9
*28.0
34.8
*20.0
31.4
*21.2
36.6
Ph endo
CNPh exo
BrPh endo
Ph exo
*17.3
42.9
*16.7
31.9
19.5
31.1
31.3
37.3
22.9
36.0
20.7
34.7
19.1
Pha endo
BrPh exo
Phb endo
BrPh exo
25.2
*15.4d
32.9
*27.0d
35.2
a Molecule 1. b Molecule 2. c Overlap is in Å3. The asterisk signifies
predicted photoproduct. Underlining signifies the observed product.
d Minor product.
Table 4. Calculated RMS Motion (Å) at the Branch Points for
Phenol Formation with Rigid and Flexible Superpositionsc
rigid super
migration to
flexible super
migration to
substrate
C-2
C-4
C-2
C-4
H endo
H exo
Me endo
Me exo
MeO endo
MeO exo
t-Bu endo
t-Bu exo
CNPh endo
Ph exo
1.60
1.59
*1.50
1.48
*1.13
2.14
*1.10
1.41
1.26
1.95
1.09
2.05
1.31
1.81
1.40d
1.73
1.28d
1.49
1.03
1.04
*0.79
1.48
*0.64
1.33
*0.72
0.95
0.75
1.28
0.73
2.05
0.81
1.16
0.76d
1.20
0.82d
0.95
1.25
1.84
0.83
1.28
Ph endo
CNPh exo
BrPh endo
Ph exo
X-ray data not available
1.78
1.82
1.78
1.75
1.78
1.81
1.43
2.15
1.28
2.17
1.34
2.26
1.13
1.08
1.08
1.08
1.08
1.12
0.82
1.38
0.75
1.35
0.72
1.36
Pha endo
BrPh exo
Phb endo
BrPh exo
a Molecule 1. b Molecule 2. c The asterisk signifies predicted pho-
toproduct. Underlining signifies the observed product. dMinor product.
(12) (a) Rice, F. O.; Teller, E. J. Chem. Phys. 1938, 6, 489-496. (b)
Hine, J. J. Org. Chem. 1966, 31, 1236-1244. (c) Hine, J. J. Am. Chem.
Soc. 1966, 88, 5525-5528. (d) Tee, O. S. J. Am. Chem. Soc. 1969, 91,
7144-7149. (e) Altman, J. A.; Tee, O. S.; Yates, K. J. Am. Chem. Soc.
1976, 98, 7132-7138.
(13) (a) Cohen, M. D. Angew. Chem., Int. Ed. Engl. 1975, 14, 386-
393. (b) Schmidt, G. M. J. Pure Appl. Chem. 1971, 27, 647-678.
(14) (a) Gavezzoti, A. Tetrahedron 1987, 43, 1241-1251. (b) Gavezotti,
A. J. Am. Chem. Soc. 1985, 107, 962-967. (c) Gavezotti, A. J. Am. Chem.
Soc. 1983, 105, 5220-5225. (d) Gavezotti, A.; Simonetta, M. NouV. J.
Chim. 1977, 2, 69. (e) Gavezotti, A.; Simonetta, M. Chem. ReV. 1982, 82,
1-13.
(15) (a) Murthy, G. S.; Arjunan, P.; Venkatesan, K.; Ramamurthy, V.
Tetrahedron 1987, 43, 1225-1240. (b) Ramamurthy, V.; Venkatesan, K.
Chem. ReV. 1987, 87, 433-481. (c) Ramamurthy, V. Photochemistry in
Organized and Constrained Media; VCH Publishers: New York, 1991.
(16) (a) McBride, J. M. Acc. Chem. Res. 1983, 16, 304-312. (b)
Kearsley, S. K.; McBride, J. M. Mol. Liq. Cryst. Inc. Nonlin. Opt. 1988,
156, 109-122.
(17) Angermund, K.; Klopp, I.; Kru¨ger, C.; Nolte, M. Angew. Chem.,
Int. Ed. Engl. 1991, 30, 1354-1355.
(18) (a) Scheffer, J. R.; Trotter, J.; Garcia-Garibay, M.; Wireko, F. Mol.
Cryst. Liq. Cryst. Incorporating Nonlinear Opt. 1988, 156, 63-84. (b)
Ariel, S.; Askarai, S.; Scheffer, J. R.; Trotter, J.; Walsh, L. J. Am. Chem.
Soc. 1984, 106, 5726-5728.
(19) Ohashi, Y.; Tomotake, Y.; Akira, U.; Sasada, Y. J. Am. Chem. Soc.
1986, 108, 1196-1202.
(20) (a) Chang, H. C.; Popovitz-Biro, R.; Lahav, M.; Lieserowitz, L. J.
Am. Chem. Soc. 1987, 109, 3883-3893. (b) Weisinger-Lewin, Y.; Vaida,
M.; Popovittz-Biro; Chang, H. C.; Mannig, F.; Frowlow, F.; Lahav, M.;
Leiserowitz, L. Tetrahedron 1987, 43, 1449-1475.
(21) Moon, C.-M.; Hasegawa, M. J. Am. Chem. Soc. 1991, 113, 7311-
7316.
(22) Thomas, N. W.; Ramadas, S.; Thomas, J. M. Proc. R. Soc. London
1985, A400, 219-227. See also ref 23.
(23) Peachey, N. M.; Eckhardt, C. J. J. Phys. Chem. 1994, 98, 7106-
7115 and earlier papers cited therein.
is the overlap of the van der Waals radii of the reacting
molecular species with the atoms of the surrounding crystal
lattice. Again the mini crystal lattice with the imbedded
intermediate zwitterion was utilized. The overlaps, ∆S values,
calculated are listed in Table 3. The agreement with experiment
is quite good. One might anticipate that the van der Waals over-
lap with the crystal lattice corresponds to the reaction molecule-
lattice interaction energy, that is, the last term in eq 1.
A final parameter we have used in attempts to quantify the
behavior of photochemistry in crystal lattices is the measurement
of RMS motion in proceeding from reactant to first intermediate.
The premise is that the preferred reaction will be the one which
involves the least motion12 of the reacting molecule. Again,
both rigid and flexible superpositions were used to generate the
reacting species and thus in determining the RMS motion. Note
Table 4. However, inspection of this table reveals a rather poor
correlation useful in dealing with previous types of solid-state
reactions in the past.
Thus, it seems that the predictive value of the energetics and
overlap provide the best approach in correlating the reaction
course in a crystal lattice with theory.
Alternative Methodology and Background. The present
research results need to be taken in perspective with earlier
findings in mind. Thus, the early work of Cohen and Schmidt13
considered 2π + 2π cycloadditions and put forth the concept
of a “reaction cavity”.13a A more quantitative suggestion made

3684 J. Am. Chem. Soc., Vol. 119, No. 16, 1997
Zimmerman and Sebek
washing four times with a mixture of 100 mL of saturated potassium
permanganate and 10 mL of sulfuric acid, water, saturated sodium
bicarbonate, and brine, drying over calcium chloride, refluxing
overnight, and distilling from calcium hydride.
cyclizations; his finding was that those pairs with higher energies
of interaction with six surrounding molecules tend to react.
Interestingly, Gavezzotti has commented16e that “the general
problem of obtaining information on solid-state reactivity from
a theoretical calculation has not yet been tackled in a systematic
way”. And, indeed, the main weakness of the literature has
been the application to a limited number of examples rather
than a broad spectrum of test cases. Additionally, the emphasis
on either reactant and/or product effects has been a problem.
Crystal lattice photochemistry is clearly kinetically controlled
in most cases.
General Procedure for Solid State Photolysis. Large crystals were
gently cracked. Crystals were spread over a strip of “Parafilm”.25 Both
the photochemical reactor and the strip with crystals were placed in a
drybox and purged with nitrogen for 1 h. The film was placed on the
cooling well of the photochemical reactor, and the edges were tied up
with Teflon tape. The cooling well was placed into the reactor flask
filled with water and purged with nitrogen 1 h before and during
photolysis. The photoreactor was placed in an ice-water bath. The
temperature of the filter solution and water in the photoreactor was
kept between 15 and 20 °C. Most of the irradiated crystals were
recovered mechanically, and the rest were obtained by a quick washing
of the Parafilm strip with a small amount of appropriate solvent.
Many additional but more qualitative treatments of reactivity
have also been described. However, an excellent general review
has been edited by Ramamurthy,18 and this covers both
qualitative and quantitative approaches.
General Procedure for X-ray Crystallography Analysis. X-ray
diffraction data were collected on a Siemens P4/CCD diffractometer
for single crystals of each compound. Lorentz and polarization
corrections were applied, and each structure was solved under the
appropriate space group symmetry by direct methods using SHELXTL
and SHELXS86.26 Hydrogen atom positions were calculated and
refined with a rigid model. Full-matrix least-squares refinement on
F2 was carried out employing anisotropic displacement parameters for
all non-hydrogen atoms and isotropic displacement parameters for all
hydrogen atoms. The coordinates for all compounds studied by X-ray
crystallography were deposited with the Cambridge Crystallographic
Data Center. The coordinates can be obtained, on request, from the
Director, Cambridge Crystallographic Data Center, 12 Union Rd.,
Cambridge, CB2 1EZ, U.K.
Turning to our own earlier studies,5,6 we note that use was
made of volume increase during reaction, least motion in
proceeding toward product, and the overlap of the transition
structure with the crystal lattice. Additionally, the transition
structure deformation energy in the lattice and the energy of
replacing a reactant molecule with a transition structure molecule
were obtained. Finally, a “lock and key” analysis was devised
to determine which points of contact of the reacting molecule
were most involved in controlling its reaction course. These
studies have utilized a large number of different reactants of
widely varying structures rather than single examples and thus
provide a sound test of the methodologies employed.
Assessment of Treatments. Firstly, it is clear that for
unimolecular rearrangements all methods are not applicable.
Secondly, in determining what reaction courses are likely, one
needs to select branch points in the reaction, most simply
alternative intermediates, each leading to different photoprod-
ucts. Although the use of final photoproducts has been
successful in cases,5 it is clear that once the transition state is
passed, control by alternative products is not relevant. Theories
based on single examples do pose a risk. Finally, one notes
that both intramolecular energy deformation and molecule-
lattice interaction energies contribute to controlling what species
may be formed in the lattice.
endo-4-Hydroxy-6,6-diphenylbicyclo[3.1.0]hexan-2-one. A 2.90
mL (2.90 mmol) solution of 1 M diisobutylaluminum hydride was added
dropwise to a stirred solution of 670 mg (2.42 mmol) of 4-methoxy-
6,6-diphenylbicyclo[3.2.1]hex-3-en-2-one7 in 50 mL of benzene at 10
°C, and the mixture was stirred for 15 min. A 10 mL portion of water
followed by 3 mL of 1.2 M HCl was added. The mixture was extracted
twice with 60 mL of ether. A 20 mL portion of THF and 20 mL of
1.2 M HCl were added to the ether extract, and the mixture was stirred
for 30 min at 20 °C. Ether extraction, washing with water, saturated
sodium bicarbonate, and water, and drying with magnesium sulfate
afforded crude product which was chromatographed on a silica gel 2.5
cm × 30 cm column. Elution with 50% ether in hexane gave 55 mg
of a mixture of unidentified products in fraction 1 and 452 mg (71%)
of endo-4-hydroxy-6,6-diphenylbicyclo[3.1.0]hexan-2-one 6 in fraction
2. Crystallization from benzene gave 412 mg (64%) of colorless
crystals, mp 193-194 °C.
Experimental Section
General Procedures. All reactions were performed under an
atmosphere of dry nitrogen. Column chromatography was performed
on silica gel (Matheson, Coleman and Bell, grade 62, 60-200 mesh)
mixed with Sylvania 2282 phosphor and slurry packed into quartz
columns to allow monitoring with a hand-held UV lamp. Preparative
thick-layer chromatography (TLC) was carried out with MN-Kiesegel
G/UV 254 silica gel (40 g of silica gel per plate, 20 cm × 20 cm)
unless stated otherwise. Plates were dried for 24 h after preparation at
room temperature. Using this kind of TLC plates is important for
successful isolation of photoproducts. Chromatography on com-
mercially available column silica gel (see above) leads to their partial
or total loss. Deactivated column silica gel was prepared by mixing
300 g of silica gel (see above) with 500 mL of water, subsequent
filtration, drying for 12 h at room temperature, and heating at 85 °C
for 3 h.
Exploratory solution photolyses were carried out with a Hanovia
450 W medium-pressure mercury lamp or a 400 W Sylvania discharge
lamp equipped with a 5 mm filter of circulating solution of 0.025 M
sodium metavanadate in 5% sodium hydroxide unless stated otherwise.
All solutions were purged with purified24 nitrogen both prior to and
during photolysis. All compounds were subjected to multiple crystal-
lizations until the melting point was constant. Tetrahydrofuran (THF)
was purified by successive distillation under a nitrogen atmosphere,
from calcium hydride, lithium aluminum hydride, and sodium-
benzophenone ketyl. Diethyl ether was dried by distillation from
sodium-benzophenone ketyl. Photograde benzene was prepared by
The spectral data were the following: 1H NMR (CDCl3, 300 MHz)
δ 7.58 (m, 2H), 7.37-7.12 (m, 8H), 5.86 (m, 1H), 3.06 (dd, J ) 5.7,
5.7 Hz, 1H), 2.66 (m, 1H), 2.36 (ddd, J ) 18.4, 9.5, 1.4 Hz, 1H), 2.05
(d, J ) 8.2 Hz, 1H), 1.36 (ddd, J ) 18.4, 8.7, 0.8 Hz, 1H). MS m/e
264.1168 (calcd for C18H16O2, 264.1150). IR (KBr) 1716 cm-1. Anal.
Calcd for C18H16O2: 81.79; H, 6.10. Found: C, 81.83; H, 6.24.
endo-6,6-Diphenyl-4-[(methylsulfonyl)oxy]bicyclo[3.1.0]hexan-2-
one. A 0.209 mL (2.70 mmol) portion of methanesulfonyl chloride
was added dropwise to a mixture of 650 mg (2.46 mmol) of endo-6,6-
diphenyl-4-hydroxybicyclo[3.2.1]hexan-2-one (6) and 0.514 mL (3.69
mmol) of triethylamine in 65 mL of dry methylene chloride at 0 °C.
The reaction mixture was stirred for 1 h and then poured into 20 mL
of 1.2 M HCl and extracted with ether. The organic layers were
collected, washed with water, sodium bicarbonate, and brine, and dried
with magnesium sulfate. Removal of solvent in vacuo afforded oil
which crystallized after addition of a small amount of ether to give
796 mg (94%) of crude product. Crystallization from benzene-hexane
gave 701 mg (83%) of colorless crystals, mp 113 °C dec.
The spectral data were the following: 1H NMR (CDCl3, 300 MHz)
δ 7.61-7.55 (m, 2H), 7.35-7.17 (m, 8H), 5.64 (ddd, J ) 9.6, 8.4, 5.8
Hz, 1H), 3.25 (dd, J ) 5.8, 5.8 Hz, 1H), 3.03 (s, 3H), 2.81 (brd, J )
5.8 Hz, 1H), 2.48 (ddd, J ) 18.4, 9.6, 1.0 Hz, 1H), 1.62 (ddd, J )
(25) Parafilm “M”, American Can Co., Greenwich, CT 06830.
(26) Sheldrick, G. M. SHELXTL Version 5 Reference Manual; Siemens
Analytical X-ray Instruments, 6300 Enterprise Dr., Madison, WI 53719-
1173, 1994.
(24) Meites, L.; Meites, T. Anal. Chem. 1948, 20, 984-985.

Photochemistry in a Crystalline Cage
J. Am. Chem. Soc., Vol. 119, No. 16, 1997 3685
18.4, 8.4, 0.8 Hz, 1H); IR (KBr) 1735, 1348, 1180 cm-1. Anal. Calcd
for C19H18SO4: C, 66.65; H, 5.30; S, 9.36. Found: C, 66.92; H, 5.61;
S, 9.37.
purification. To a solution of 2.37 g of crude 4-(p-cyanophenyl)-4-
phenyl-6-(phenylseleno)cyclohex-2-en-1-one in 20 mL of dichlo-
romethane and 1.10 mL of pyridine was added 1.70 mL (15.0 mmol)
of 30% H2O2. The solution was stirred at room temperature for 2 h,
diluted with ether, washed with saturated aqueous sodium bicarbonate,
1.2 N HCl, and brine, dried with magnesium sulfate, and concentrated
in vacuo. The crude product, 1.19 g, was chromatographed on a 3 cm
× 30 cm silica gel column eluted with 30% ether in hexane. Fraction
1 gave 0.18 g of a mixture of unknown compounds. Fraction 2 gave
0.881 g (57%) of 4-(p-cyanophenyl)-4-phenylcyclohexa-2,5-dienone (9).
Crystallization from hexane afforded 0.675 mg (44%) of colorless
crystals, mp 151-153 °C (lit.4d mp 152-153 °C).
3-Methyl-4,4-diphenylcyclohexa-2,5-dienone (12b). The general
method of Reich et al.27 was used. To a -78 °C of LDA (prepared by
the addition of 1.95 mL (4.57 mmol) of 2.35 M n-butyllithium in hexane
to 0.671 mL (4.57 mmol) of diisopropylamine in 17 mL of THF) was
added a solution of 1.0 g (3.81 mmol) of 3-methyl-4,4-diphenylcyclo-
hex-2-en-1-one (11b)29 in 5 mL of THF. The solution was stirred at
-78 °C for 15 min, and a solution of 4.58 mmol of phenylselenyl
bromide (prepared by addition of 0.118 mL (2.29 mmol) of bromine
to 0.715 g (2.29 mmol) of PhSeSePh in 5 mL of THF) was added in
one portion. The reaction mixture was stirred for 5 min and poured
into 50 mL of diethyl ether and 50 mL of 0.5 M HCl. Ether extraction,
washing with saturated aqueous sodium bicarbonate and brine, drying
with anhydrous magnesium sulfate, and concentrating in vacuo gave
0.711 g of oil which was used without further purification. The crude
product was dissolved in a mixture of 7 mL of dichloromethane and
0.28 mL of pyridine, and 0.55 mL (4.84 mmol) of 30% H2O2 was added.
The solution was stirred at room temperature for 2 h, diluted with ether,
washed with saturated aqueous sodium bicarbonate, 1.2 N HCl, and
brine, dried with magnesium sulfate, and concentrated in vacuo to give
0.411 g (41%) of crude product. Crystallization from hexane afforded
318 mg (32%) of 3-methyl-4,4-diphenylcyclohexa-2,5-dienone (12b)
as colorless crystals, mp 121-122 °C.
6,6-Diphenylbicyclo[3.1.0]hex-3-en-2-one (5a). A 1.13 g (3.30
mmol) portion of endo-6,6-diphenyl-4-[(methylsulfonyl)oxy]bicyclo-
[3.1.0]hexan-2-one was dissolved in 85 mL of dry THF, and 391 mg
(3.48 mmol) of t-BuOK was added at 20 °C. The reaction mixture
was stirred for 30 min and then poured into 100 mL of water and
extracted with ether. The combined organic layers were washed with
brine, dried with magnesium sulfate, and evaporated under vacuum.
Chromatography of crude product on a 3 cm × 25 cm silica gel column
eluted with 20% ether in hexane gave 149 mg (18%) of 6,6-
diphenylbicyclo[3.1.0]hex-3-en-2-one (5a). Crystallization from hep-
tane gave 132 mg (16%) of colorless crystals, mp 140-141 °C (lit.8
mp 140.0-140.2 °C).
4-Methyl-6,6-diphenylbicyclo[3.1.0]hex-3-en-2-one (5b). To a
-78 °C solution of 4.0 g (9.34 mmol) of 4-(diphenylmethoxy)-6,6-
diphenylbicyclo[3.1.0]hex-3-en-2-one (5e)7 in 95 mL of THF was added
10.0 mL of 1.4 M methyllithium in ether (14.0 mmol). The solution
was stirred at -78 °C for 15 min, and 150 mL of water was added.
The mixture was allowed to warm to 5 °C, 65 mL of 6 N HCl was
added, and the mixture was stirred at room temperature for 1 h. Ether
extraction, washing of the organic phase with saturated sodium
bicarbonate, brine, and water, and drying with magnesium sulfate
afforded 3.64 g of a white oil. Chromatography on a 4 cm × 30 cm
silica gel column eluted with 10% ether in hexane afforded 1.53 g (89%)
of diphenylmethanol (pure by NMR) in fraction 1. Fraction 2 gave
1.75 g (72%) of 3-methyl-6,6-diphenylbicyclo[3.1.0]hex-3-en-2-one
(5b). Crystallization of enone 5b from heptane gave 1.53 g (63%) of
colorless crystals, mp 140-141 °C.
The spectral data were the following: 1H NMR (CDCl3, 300 MHz)
δ 7.22-7.14 (m, 10 H), 5.28 (m, 1 H), 3.10 (d, J ) 4.7, 1 H), 2.76
(dd, J ) 4.7, 1.0 Hz, 1H), 2.12 (d, J ) 1.2 Hz, 3H); IR (KBr) 1697,
1612 cm-1
. UV (MeCN) λ(max) ) 340 nm (ꢀ ) 176); MS m/e
The spectral data were the following: 1H NMR (CDCl3, 300 MHz)
δ 7.38-7.08 (m, 10H), 7.10 (d, J ) 9.3 Hz, 1H), 6.33 (m, 1H), 6.26
(dd, J ) 9.3, 1.5 Hz, 1H), 1.83 (d, J ) 1.5 Hz, 3H); MS m/e 260.1213
(calcd for C19H16O, 260.1201); IR (KBr) 1650, 1617 cm-1. Anal. Calcd
for C19H16O: C, 87.66; H, 6.19. Found: C, 87.50 H; 6.13.
3-Methyl-4,5-diphenylphenol (13b). Acid-Catalyzed Isomeriza-
tion of 3-Methyl-4,4-diphenylcyclohexa-2,5-dienone (12b). The
general procedure of Zimmerman et al.4b was used. A mixture of 100
mg (0.38 mmol) of 3-methyl-4,4-diphenylcyclohexa-2,5-dienone (12b),
1.5 mL of glacial acetic acid, 0.2 mL of water, and 0.5 mL of
concentrated HCl was heated at 120 °C for 2 h. The solution was
cooled, diluted with 25 mL of water, and extracted with chloroform.
The extract was washed with water and brine, dried with magnesium
sulfate, and concentrated under vacuum. Crystallization of the crude
product from hexane gave 82 mg (82%) of 3-methyl-4,5-diphenylphenol
(13b) as colorless crystals, mp 109-110 °C.
260.1203 (calcd for C19H16O, 260.1201). Anal. Calcd for C19H16O:
C, 87.66; H, 6.19. Found: C, 87.38; H, 6.07.
4-tert-Butyl-6,6-diphenylbicyclo[3.1.0]hex-3-en-2-one (5d). To a
-78 °C solution of 1.50 g (5.43 mmol) of 4-methoxy-6,6-diphenyl-
bicyclo[3.1.0.]hex-3-en-2-one (5d)7 in 45 mL of THF was added 4.15
mL of 1.7 M tert-butyllithium in ether (7.06 mmol). The solution was
stirred at -78 °C for 15 min, and 75 mL of water was added. The
mixture was allowed to warm to 5 °C, 90 mL of 6 N HCl was added,
and the mixture was stirred at room temperature for 1 h. Ether
extraction, washing of the organic phase with saturated sodium
bicarbonate, brine, and water, and drying with magnesium sulfate
afforded crude product. Chromatography on a 3 cm × 40 cm silica
gel column eluted with 10% ether in hexane and crystallization from
heptane gave 1.27 g (77%) of 4-tert-butyl-6,6-diphenylbicyclo[3.1.0]-
hex-3-en-2-one (5d) as colorless crystals, mp 91-92 °C.
The spectral data were the following: 1H NMR (CDCl3, 300 MHz)
7.36-7.15 (m, 10H), 5.39 (m, 1H), 3.28 (d, J ) 5.0, 1.0 Hz, 1H), 2.69
The spectral data were the following: 1H NMR (CDCl3, 300 MHz)
δ 7.22-6.99 (m, 9H, arom), 6.79 (d br, J ) 2.7 Hz, 1H), 6.78 (d br,
J ) 2.7 Hz, 1H), 6.74 (d br, J ) 2.7 Hz, 1H), 4.68 (s, 1H), 2.13 (s,
3H); MS m/e 260.1200 (calcd for C19H16O, 260.1201); IR (KBr) 3150-
3600, 1577, 1469, 1327, 1250, 1176, 1072, 1006 cm-1. Anal. Calcd
for C19H16O: C, 87.66; H, 6.19. Found: C, 87.26; H, 6.19.
3-Methyl-4,5-diphenylphenol (13b). Oxidation of 3-Methyl-4,5-
diphenylcyclohex-2-en-1-one (15). A mixture of 100 mg (0.38 mmol)
of 3-methyl-4,5-diphenylcyclohex-2-en-1-one (15) and 116 mg (0.56
mmol) of DDQ in 10 mL of dioxane was refluxed for 31 h. The
mixture was cooled and filtered quickly through a 5 cm × 2 cm silica
gel column eluted with diethyl ether, and the solvent was removed in
vacuo. Chromatography of the residue on a preparative TLC plate
eluted with 7% ether in hexane afforded 24 mg (24%) of 3-methyl-
4,5-diphenylphenol (13b). Crystallization from hexane gave colorless
crystals, mp 107-109 °C.
(dd, J ) 5.0, 1.3 Hz, 1H), 1.18 (s, 9H); IR (KBr) 1691, 1591 cm-1
;
UV (MeCN) λ(max) ) 345 nm (ꢀ ) 162); MS m/e 302.1678 (calcd
for C22H22O, 302.1671). Anal. Calcd for C22H22O: C, 87.38; H, 7.33.
Found: C, 87.57 H, 7.21.
4-(p-Cyanophenyl)-4-phenylcyclohexa-2,5-dienone (9). The gen-
eral method of Reich et al.27 was used. To a -78 °C of LDA (prepared
by the addition of 4.77 mL (6.68 mmol) of 1.40 M methyllithium in
hexane to 0.936 mL (6.68 mmol) of diisopropylamine in 32 mL of
THF) was added a solution of 1.52 g (5.56 mmol) of 4-(p-cyanophenyl)-
4-phenylcyclohex-2-en-1-one (8)28 in 24 mL of THF. The solution
was stirred at -78 °C for 15 min, and a solution of 6.68 mmol of
phenylselenyl bromide (prepared by addition of 0.171 mL (3.34 mmol)
of bromine to 1.04 g (3.34 mmol) of PhSeSePh in 5 mL of THF) was
added in one portion. The reaction mixture was stirred for 5 min and
poured into 50 mL of diethyl ether and 50 mL of 0.5 M HCl. Ether
extraction, washing with saturated aqueous soduim bicarbonate and
brine, drying with anhydrous magnesium sulfate, and concentrating in
vacuo gave 2.37 g of crude product which was used without further
3-Methyl-4,5-diphenylcyclohex-2-en-1-one (15). To a -78 °C
solution of 120 mg (0.43 mmol) of 3-methoxy-5,6-diphenylcyclohex-
2-en-1-one (14)30 in 3 mL of THF was added 0.40 mL of 1.4 M
(27) Reich, H. J.; Renga, J. M.; Reich, I. L. J. Am. Chem. Soc. 1975,
97, 5434.
(28) Zimmerman, H. E.; Rieke, R. D.; Scheffer, J. S. J. Am. Chem. Soc.
1967, 89, 2033.
(29) Zimmerman, H. E.; Solomon, R. D. J. Am. Chem. Soc. 1986, 108,
6276-6289.
(30) Zimmerman, H. E.; Pasteris, R. J. J. Org. Chem. 1980, 45, 4876-
4891.

3686 J. Am. Chem. Soc., Vol. 119, No. 16, 1997
Zimmerman and Sebek
methyllithium in ether (0.56 mmol). The solution was stirred at -78
°C for 15 min and then 5 mL of water added. The mixture was allowed
to warm to 20 °C, 2 mL of 6 N HCl was added, and the mixture was
stirred at room temperature for 1 h. Ether extraction, washing of the
organic phase with saturated sodium bicarbonate, brine, and water, and
drying with magnesium sulfate afforded crude product. Chromatog-
raphy on a TLC preparative plate eluted with 20% ether in hexane
gave 101 mg (90%) of 3-methyl-5,6-diphenylcyclohex-2-en-1-one (15).
Crystallization from pentane gave 77.2 mg (69%) of colorless crystals,
mp 65-67 °C.
acetic acid, 0.13 mL of water, and 0.33 mL of concentrated HCl was
refluxed for 30 min. The solution was cooled, diluted with 100 mL of
water, and extracted with ether. The extract was washed with brine
and water, dried with magnesium sulfate, and concentrated under vacuo.
Crystallization of the crude product from heptane gave 58.0 mg (83%)
of 3-tert-butyl-4,5-diphenylphenol (13d) as colorless crystals, mp 141-
143 °C.
The spectral data were the following: 1H NMR (CDCl3, 300 MHz)
δ 7.10-6.91 (m, 11H), 6.67 (d, J ) 2.7 Hz, 1H), 4.88 (s, 1H), 1.17 (s,
9H); MS m/e 302.1675 (calcd for C22H22O, 302.1671); IR (film) 3150-
3600, 1602, 1583, 1495, 1483, 1440, 1425, 1363, 1319, 1252, 1200,
1178 cm-1. Anal. Calcd for C22H22O: C, 87.38; H, 7.33. Found: C,
87.31; H, 7.35.
6,6-Diphenylcyclohexa-2,4-dienone (16a). A 1.30 mL (1.30 mmol)
sample of a 1 M solution of diisobutylaluminium hydride in hexane
was added dropwise into a solution of 300 mg (1.09 mmol) of 4,4-
diphenyl-3-methoxycyclohexa-2,5-dienone30 in 20 mL of dry benzene
at 10 °C, and the mixture was stirred for 15 min. A 100 mL portion
of water followed by 3 mL of 1.2 M HCl was added. The mixture
was extracted with ether and washed with water, and the solvents were
removed in vacuo. The residue was dissolved in 30 mL of THF, 15
mL of 1.2 M HCl was added, and the solution was stirred for 30 min
at 20 °C. Ether extraction, washing with water, saturated sodium
bicarbonate, and water, and drying with magnesium sulfate afforded
298 mg of oil. Chromatography of the crude mixture on a silica gel
2.5 cm × 36 cm column gave 126 mg (47%) of 6,6-diphenylcyclohexa-
2,4-dienone (16a). Crystallization of dienone 16a from hexane gave
106 mg (39%) of colorless crystals, mp 98.0-98.5 °C.
The spectral data were the following: 1H NMR (CDCl3, 300 MHz)
δ 7.28 -7.12 (m, 6H), 7.06-7.02 (m, 4H), 6.19 (m, 1H), 3.73 (d br,
J ) 7.7 Hz, 1H), 3.42 (ddd, J ) 9.5, 7.7, 5.4 Hz, 1H), 2.77 (dd, J )
16.4, 9.5 Hz, 1H), 2.69 (dd, J ) 16.4, 5.4 Hz, 1H), 1.76 (m, 3H); MS
m/e 262.1347 (calcd for C19H18O, 262.1361); IR (KBr) 1664, 1629
cm-1. Anal. Calcd for C19H18O: C, 86.99; H, 6.92. Found: C, 87.14;
H, 7.02.
3-tert-Butyl-4,4-diphenylcyclohex-2-en-1-one (11d). To a solution
of 1.50 g (5.39 mmol) of 3-methoxy-6,6-diphenylcyclohex-2-en-1-one
(10)29 in 45 mL of THF at -78 °C was added 4.12 mL of 1.7 M tert-
butyllithium in pentane (7.01 mmol). The solution was stirred at -78
°C for 15 min and then 75 mL of water added followed by 90 mL of
6 N HCl. The mixture was allowed to warm to 20 °C and stirred at
room temperature for 1 h. Ether extraction, washing of the organic
phase with saturated sodium bicarbonate, brine, and water, and drying
with magnesium sulfate afforded crude product which after chroma-
tography on a silica gel 3 × 25 cm column eluted with 10% ether in
hexane afforded 1.31 g (80%) of 3-tert-butyl-4,4-diphenylcyclohex-2-
en-1-one (11d). Crystallization from heptane gave 1.18 g (72%) of
colorless crystals, mp 159-160 °C.
The spectral data were the following: 1H NMR (CDCl3, 300 MHz)
δ 7.34-7.16 (m, 10 H), 7.10 (ddd, J ) 9.7, 5.8, 1.8 Hz, 1H), 6.75
(ddd, J ) 9.4, 1.8, 0.8 Hz, 1H), 6.39 (ddd, J ) 9.4, 5.8, 0.8 Hz, 1H),
6.10 (ddd, J ) 9.7, 0.8, 0.8, 1H); MS m/e 246.1055 (calcd for C18H14O,
246.1045); IR (film) 1664, 1633 cm-1. Anal. Calcd for C18H14O: C,
87.78; H, 5.73. Found: C, 87.65; H, 5.99.
The spectral data were the following: 1H NMR (CDCl3, 300 MHz)
δ 7.46-7.25 (m, 10H), 6.53 (s, 1H), 2.64 (m, 2H), 2.03 (m, 2H), 0.96
(s, 9H); MS m/e 304.1821 (calcd for C22H24O, 304.1828); IR (film)
1671, 1579 cm-1. Anal. Calcd C22H24O: C, 86.80; H, 7.94. Found:
C, 87.17; H, 8.17.
3-tert-Butyl-6,6-diphenylcyclohexa-2,4-dienone (16d). A 0.275
mL (0.468 mmol) portion of 1.7 M t-BuLi in pentane was added
dropwise into a solution of 100 mg (0.36 mmol) of 3-methoxy-4,4-
diphenylcyclohexa-2,5-dienone (12c)30 in 4 mL of THF at -78 °C.
The solution was stirred for 15 min. A 6 mL portion of water followed
by 2 mL of 6 N HCl was added and the mixture allowed to warm to
20 °C and stirred for 1 h. Ether extraction, washing with sodium
bicarbonate and water, and drying with magnesium sulfate gave crude
product which was purified by chromatography on a silica gel 2.5 cm
× 17 cm column. Elution with 5% ether in hexane afforded 34.2 mg
(31%) of 3-tert-butyl-6,6-diphenylcyclohexa-2,4-dienone (16d) in frac-
tion 1. Crystallization from pentane gave 24.5 mg (23%) of colorless
crystals, mp 108-109 °C. Fraction 2 contained 36.1 mg (30%) of
5-tert-butyl-3-methoxy-4,4-diphenylcyclohex-2-en-1-one (17). Crystal-
lization from hexane gave 32.8 mg (27%) of colorless crystals, mp
154-155 °C.
3-tert-Butyl-4,4-diphenylcyclohexa-2,5-dienone (12d). The general
method of Reich et al.27 was used. To a -78 °C of LDA (prepared by
addition of 0.84 mL (1.97 mmol) of 2.35 M n-BuLi in hexane to 0.276
mL (1.97 mmol) of diisopropylamine in 8 mL of THF) was added a
solution of 500 mg (1.64 mmol) of 3-tert-butyl-4,4-diphenylcyclohex-
2-en-1-one (11d) in 5 mL of THF. The solution was stirred at -78
°C for 15 min, and a solution of 1.96 mmol of phenylselenyl bromide
(prepared by addition of 0.050 mL (0.98 mmol) of bromine to 306 mg
(0.98 mmol) of PhSeSePh in 4 mL of THF) was added in one portion.
The reaction mixture was stirred for 5 min and poured into 100 mL of
diethyl ether and 100 mL of 1.2 M HCl. Ether extraction, washing
with saturated aqueous sodium bicarbonate and brine, drying with
magnesium sulfate, and concentrating in vacuo gave yellow oil.
Column chromatography of the crude product on a 3 cm × 40 cm
silica gel column eluted with 5% ether in hexane gave 75 mg of a
mixture of unidentified compounds in fraction 1. Fraction 2 afforded
472 mg of an oil. Fraction 3 contained 35 mg (7%) of starting enone
11d. Fraction 2 was dissolved in a mixture of 4 mL of methylene
chloride and 0.20 mL of pyridine, and 0.30 mL (2.64 mmol) of 30%
hydrogen peroxide was added. The reaction mixture was stirred for 2
h at 20 °C. The mixture was poured into 100 mL of ether with 100
mL of saturated sodium bicarbonate, extracted with ether, washed with
brine and water, dried with magnesium sulfate, and evaporated in
vacuo. Chromatography of the crude product on a silica gel 3 × 20
cm column eluted with 10% ether in hexane afforded 51 mg of
unidentified compound in fraction 1. Fraction 2 contained 208 mg
(42%) of 3-tert-butyl-4,4-diphenylcyclohexa-2,5-dienone (12d). Crys-
tallization from heptane gave 169 mg (34%) of colorless crystals, mp
142-143 °C.
The spectral characteristics of 3-tert-butyl-6,6-diphenylcyclohexa-
2,4-dienone (16d) were the following: 1H NMR (CDCl3, 300 MHz) δ
7.32-7.20 (m, 10H), 6.70 (dd, J ) 9.8, 0.6 Hz, 1H) 6.52 (dd, J ) 9.8,
1.6 Hz, 1H), 6.00 (dd, J ) 1.6, 0.6 Hz, 1H), 1.21 (s, 9H, t-Bu); MS
m/e 302.1680 (calcd for C22H22O, 302.1671); IR (film) 1652, 1564 cm-1
.
Anal. Calcd for C22H22O: C, 87.38; H, 7.33. Found: C, 87.55; H,
7.38.
The spectral characteristics of 5-tert-butyl-3-methoxy-4,4-diphenyl-
cyclohex-2-en-1-one (17) were the following: 1H NMR (CDCl3, 300
MHz) δ 7.63-7.50 (m, 4H), 7.43-7.22 (m, 6H), 5.58 (s, 1H), 3.44 (s,
3H), 3.21 (dd, J ) 12.5, 3.3 Hz, 1H), 2.50 (dd, J ) 16.4, 3.3 Hz, 1H),
2.40 (dd, J ) 16.4, 12.5 Hz, 1H), 0.56 (s, 9H); MS m/e 334.1937 (calcd
for C23H26O2, 334.1933); IR (film) 1649, 1598, 1211 cm-1. Anal. Calcd
for C23H26O2: C, 82.60; H, 7.84. Found: C, 82.81; H, 7.58.
3-Methoxy-6,6-diphenylcyclohexa-2,4-dienone (16c). A mixture
of 420 mg (1.51 mmol) of 3-methoxy-6,6-diphenylcyclohex-2-en-1-
one (10c),30 411 mg (1.81 mmol) of DDQ, and 1 mg of p-toluene-
sulfonic acid in 15 mL of benzene was refluxed for 97 h. The reaction
mixture was cooled and poured into a mixture of 30 mL of ether and
30 mL of water. The organic layer was separated, washed with 10%
NaOH, water, and brine, and dried with magnesium sulfate. Chroma-
tography of the crude product on a 18 cm × 3 cm silica gel column
eluted with 10% ether in hexane afforded 270 mg (65%) of solid.
The spectral characteristics were the following: 1H NMR (CDCl3,
300 MHz) δ 7.51-7.26 (m, 10H), 6.85 (d, J ) 9.7 Hz, 1H), 6.74 (d,
J ) 1.7 Hz, 1H), 6.02 (dd, J ) 9.7, 1.7 Hz, 1H), 0.92 (s, 9 H); MS m/e
302.1669 (calcd for C22H22O, 302.1671); IR (film) 1654, 1619 cm-1
.
Anal. Calcd for C22H22O: C, 87.38; H, 7.33. Found: C, 87.56; H,
7.61.
3-tert-Butyl-4,5-diphenylphenol (13d). The general procedure of
Zimmerman et al.4b was used. A mixture of 70 mg (0.23 mmol) of
3-tert-butyl-4,4-diphenylcyclohexa-2,5-dienone (12d), 1.0 mL of glacial

Photochemistry in a Crystalline Cage
J. Am. Chem. Soc., Vol. 119, No. 16, 1997 3687
Crystallization twice from hexane-benzene gave 178 mg (43%) of
3-methoxy-6,6-diphenylcyclohexa-2,4-dienone (16c) as colorless crys-
tals, mp 131-132 °C.
5.3, 1.3 Hz, 1H); MS m/e 356.0332 (calcd for C19H15O2Br, 356.0238);
IR (film) 1684, 1587, 1371, 1236 cm-1. Anal. Calcd for C19H15O2-
Br: C, 64.24; H, 4.26; Br, 22.49. Found: C, 64.26; H, 4.32; Br, 22.90.
Exploratory Solution Photolysis of 6,6-Diphenylbicyclo[3.1.0]hex-
3-en-2-one (5a). A solution of 117 mg (0.48 mmol) of 6,6-
diphenylbicyclo[3.2.1]hex-3-en-2-one (5a) in 120 mL of benzene was
irradiated for 40 min. The solvent was removed in vacuo and the crude
mixture chromatographed on a preparative silica gel TLC plate eluted
with 5% ether in hexane. Band 1 (9.8 mg, 8.4%) contained 2,3-
diphenylphenol (20a). Crystallization from hexane gave mp 101-102
°C (lit.8 mp 102.2-103.2 °C). Band 2 (42.8 mg, 36.6%) contained
6,6-diphenylcyclohexa-2,4-dienone (16a). Crystallization from heptane
gave 29.4 mg (25.1%) of crystals, mp 98-99 °C. The third band gave
15.1 mg (13%) of starting 6,6-diphenylbicyclo[3.2.1]hex-3-en-2-one
(5a) together with unidentified impurities.
Exploratory Solution Photolysis of 4-Methyl-6,6-diphenylbicyclo-
[3.1.0]hex-3-en-2-one (5b). A solution of 250 mg (0.95 mmol) of
4-methyl-6,6-diphenylbicyclo[3.1.0]hex-3-en-2-one (5b) in 200 mL of
photolysis grade benzene was irradiated for 30 min. The crude mixture
was chromatographed on two preparative TLC plates (20 cm × 20
cm, 20 g of TLC silica gel per plate) eluted with 7% ether in hexane.
Band 1 (22.0 mg, 8.8%) contained 5-methyl-2,3-diphenylphenol (20b).
Two-fold crystallization from hexane gave 10.3 mg (4.1%) of colorless
crystals, mp 126-127 °C. Band 2 gave 43.9 mg (17.6%) of 3-methyl-
6,6-diphenylcyclohexa-2,4-dienone (16b) as an oil. Slow evaporation
of the hexane solution gave 29.2 mg (11.7%) of colorless crystals, mp
61-62 °C. Band 3 contained 126.6 mg (50.6%) of starting 4-methyl-
6,6-diphenylbicyclo[3.1.0]hex-3-en-2-one (5b).
The spectral data were the following: 1H NMR (CDCl3, 300 MHz)
δ 7.33-7.16 (m, 10H), 6.76 (d, J ) 10.1 Hz, 1H), 6.26 (dd, J ) 10.1,
2.1 Hz, 1H), 5.52 (d, J ) 2.1 Hz, 1H), 3.81 (s, 3H); MS m/e 276.1152
(calcd for C19H16O2, 276.1150); IR (film) 1652, 1573, 1240 cm-1. Anal.
Calcd for C19H16O2: C, 82.59; H, 5.84. Found: C, 82.60; H, 6.12.
4-(p-Cyanophenyl)-3-phenylphenol (19). A mixture of 150 mg
(0.552 mmol) of 4-(p-cyanophenyl)-4-phenylcyclohexa-2,5-dienone (18)
and 35 mg (0.18 mmol) of p-toluenesulfonic acid monohydrate was
stirred at 120 °C for 5 min. Chromatography on a 70 × 1 cm silica
gel column eluted with 20% ether in hexane afforded 44.0 mg (29.3%)
of 4-(p-cyanophenyl)-3-phenylphenol in fraction 1. Crystallization from
benzene-heptane gave 33.5 mg (13.4%) of colorless crystals, mp 271-
272 °C. Fraction 2 gave 4.3 mg of a mixture of 3-(p-cyanophenyl)-
4-phenylphenol (29) and an unidentified compound (by NMR).
The spectral characteristics of 4-(p-cyanophenyl)-3-phenyphenol (19)
were the following: 1H NMR (CDCl3, 300 MHz): δ 7.47 (m, 2H),
7.30-7.21 (m, 4H), 7.18 (m, 2H), 7.12-7.05 (m, 2H), 6.95-6.90 (m,
2H), 5.10 (s, 1H). MS m/e 271.1009 (calcd for C19H13NO, 271.0997);
IR (KBr) 3150-3500, 2229, 1602, 1583, 1569, 1483, 1450, 1432, 1309,
1199 cm-1. Anal. Calcd for C19H13NO: C, 84.11; H, 4.83; N, 5.16.
Found: C, 84.20; H, 5.01; N, 5.04.
(p-Bromophenyl)phenyldiazomethane. (p-Bromophenyl)phenyl-
diazomethane was prepared by the general procedure of Miller.31
A
mixture of 40.3 g (0.146 mol) of (p-bromophenyl)benzophenone
hydrazone, 19.6 g of anhydrous sodium sulfate, 420 mL of ether, 59.0
g (0.272 mol) of yellow mercuric oxide, and 22.5 mL of ethanol
saturated with potassium hydroxide was stirred for 24 h. The reaction
mixture was filtered and 500 mL of pentane added. The solution was
extracted with 200 mL of water and dried with magnesium sulfate.
Solvent was removed in vacuo to give 31.2 g (78%) of (p-bromo-
phenyl)phenyldiazomethane as a red solid which was used without
further purification.
The spectral data for 3-methyl-6,6-diphenylcyclohexa-2,4-dienone
(16b) were the following: 1H NMR (CDCl3, 300 MHz) δ 7.36-7.17
(m, 10H), 6.69 (d, J ) 9.6 Hz, 1H), 6.24 (dd, J ) 9.6, 1.2 Hz, 1H),
5.95 (m, 1H), 2.10 (d, J ) 1.2, 3H); MS m/e 260.1205 (calcd for
C19H16O, 260.1201); IR (film) 1650, 1570 cm-1
. Anal. Calcd for
C19H16O: C, 87.66; H, 6.19. Found: C, 87.83; H, 6.34. The structure
assignment was supported by X-ray diffraction (see the Supporting
Information). The spectral data for 3-methyl-5,6-diphenylphenol (20b)
were the following: 1H NMR (CDCl3, 300 MHz) δ 7.36-7.22 (m,
4H), 7.19-7.02 (m, 6H), 6.83-6.88 (m, 2H), 5.06 (s, 1H), 2.40 (s,
3H); MS m/e 260.1206 (calcd for C19H16O, 260.1201). Anal. Calcd
for C19H16O: C, 87.66; H, 6.19. Found: C, 87.34; H, 6.29.
Exploratory Solution Photolysis of 4-Methoxy-6,6-diphenylbicyclo-
[3.1.0]hex-3-en-2-one (5c). A solution of 250 mg (0.90 mmol) of
4-methoxy-6,6-diphenylbicyclo[3.1.0]hex-3-en-2-one (5c)7 in 250 mL
of photolysis grade benzene was irradiated for 30 min. Solvent was
removed in vacuo and the crude mixture separated by preparative
chromatography on a TLC plate eluted with 10% ether in hexane. Band
1 (12.9 mg, 5.2%) contained 3-methoxy-5,6-diphenylphenol. Crystal-
lization from hexane afforded 9.1 mg (3.6%) of colorless crystals, mp
115-117 °C (lit.30 mp 115.5-117 °C). Band 2 (14.7 mg, 5.9%)
contained 3-methoxy-6,6-diphenylcyclohexa-2,4-dienone (16c). Crys-
tallization from hexane yielded 10.0 mg (4.0%) of colorless crystals,
mp 130-132 °C. Band 3 gave 179 mg (71.6%) of starting 4-methoxy-
6,6-diphenylbicyclo[3.1.0]hex-3-en-2-one (5c).
Exploratory Solution Photolysis of 4-tert-Butyl-6,6-diphenyl-
[3.2.1]cyclohex-3-en-2-one (5d). A 150 mg (4.96 mmol) sample of
4-tert-butyl-6,6-diphenyl[3.2.1]cyclohex-3-en-2-one (5d) in 150 mL of
benzene was irradiated for 25 min. Solvent was removed in vacuo
and the mixture separated on a preparative TLC silica gel plate eluted
with 5% ether in hexane. Band 1 gave 17.9 mg (11.9%) of 3-tert-
butyl-5,6-diphenylphenol (20d). Crystallization from hexane afforded
13.6 mg (9.1%) of colorless crystals, mp 149-150 °C. Band 2
contained 31.1 mg (20.7%) of 3-tert-butyl-6,6-diphenylcyclohexa-2,4-
dienone (16d) as an oil. Slow evaporation of the pentane solution gave
15.2 mg (10.1%) of colorless crystals, mp 105-107 °C. The third
band gave 81.9 mg (54.6%) of starting 4-tert-butyl-6,6-diphenylbicyclo-
[3.2.1]cyclohex-3-en-2-one (5d).
The spectral characteristics of 3-tert-butyl-5,6-diphenylphenol (5d)
were the following: 1H NMR (CDCl3, 300 MHz) δ 7.34-7.03 (m,
12H), 5.10 (s, 1H), 1.38 (s, 9H); IR (film) 3150-3600, 1616, 1577,
1558, 1479, 1407, 1301, 1186 cm-1; MS m/e 302.1680 (calcd for
C22H22O, 302.1671). Anal. Calcd for C22H22O: C, 87.38; H, 7.33.
Found: C, 87.06; H, 7.10. The structure assignment was supported
by X-ray diffraction (see the Supporting Information).
6-exo-(p-Bromophenyl)-4-methoxy-6-endo-phenylbicyclo[3.1.0]-
hex-3-en-2-one (24a) and 6-endo-(p-Bromophenyl)-4-methoxy-6-exo-
phenylbicyclo[3.1.0]hex-3-en-2-one (24b). A 4.0 g (41.7 mmol)
portion of cyclopent-2-ene-1,4-dione32 was added into a solution of
24.0 g (87.9 mmol) of (p-bromophenyl)phenyldiazomethane in 150 mL
of dry benzene. The mixture was stirred at room temperature for 12 h
and then refluxed for 3 h. The solvent was removed in vacuo and the
mixture chromatographed on a 5.5 cm × 50 cm silica gel column eluted
with 20% ether in hexane to give 19.8 g of a mixture of enones 7a (Ar
) p-bromophenyl) and 7b (Ar ) p-bromophenyl) as a yellow oil. The
mixture was dissolved in 300 mL of dry methanol, 100 mg of
p-toluenesulfonic acid was added, and the solution was refluxed for
12 h. Solvent was removed in vacuo and the residue chromatographed
on a 4 cm × 90 cm silica gel column eluted with 20% ether in hexane.
Fraction 1 afforded 6.3 g of 1-(p-bromophenyl)-1-phenylmethyl methyl
ether. Fraction 2 gave 3.32 g (22%) of 6-endo-(p-bromophenyl)-4-
methoxy-6-exo-phenylbicyclo[3.1.0]hex-3-en-2-one (24a). Crystal-
lization from ether yielded 2.94 g (20%) of colorless crystals, 134-
135 °C. Fraction 3 gave 0.712 g (5%) of a mixture of enone 24a and
enone 24b. Fraction 4 afforded 3.98 g (27%) of 6-exo-(p-bromophen-
yl)-4-methoxy-6-endo-phenylbicyclo[3.1.0]hex-3-en-2-one (24b). Crys-
tallization from hexane-benzene afforded 3.40 g (23%) of colorless
crystals, mp 139-140 °C.
The spectral characteristics of 6-exo-(p-bromophenyl)-4-methoxy-
6-endo-phenylbicyclo[3.1.0]hex-3-en-2-one (24a) were the following:
NMR (300 MHz, CDCl3) δ 7.43-7.19 (m, 7H), 7.07 (m, 2H), 4.54
(m, 1H), 3.62 (s, 3H), 2.97 (dd, J ) 5.3, 0.9 Hz, 1H), 2.79 (dd, J )
5.3, 1.4 Hz, 1H); MS m/e 356.0226 (calcd for C19H15O2Br, 356.0238);
IR (film) 1684, 1587, 1371, 1236 cm-1. Anal. Calcd for C19H15O2-
Br: C, 64.24; H, 4.26; Br, 22.49. Found: C, 64.11; H, 4.44; Br, 22.50.
The spectral characteristics of 6-endo-(p-bromophenyl)-4-methoxy-
6-exo-phenylbicyclo[3.1.0]hex-3-en-2-one (24b) were the following:
1H NMR (CDCl3, 300 MHz) δ 7.40 (m, 2H), 7.30-7.14 (m, 7H), 4.57
(m, 1H), 3.65 (s, 3H), 3.01 (dd, J ) 5.3, 1.1 Hz, 1H), 2.84 (dd, J )
(31) Miller, J. B. J. Org. Chem. 1959, 24, 560-561.
(32) Rasmussen, G. H.; House, H. O.; Zaweski, E. F.; De Puy, C. H.
Organic Syntheses; Wiley: New York, 1973; Collect. Vol. V, pp 324-
332.

3688 J. Am. Chem. Soc., Vol. 119, No. 16, 1997
Zimmerman and Sebek
Exploratory Solution Photolysis of 6,6-Diphenyl-4-(diphenyl-
methoxy)bicyclo[3.1.0]hex-3-en-2-one (5e). A solution of 227 mg
(0.53 mmol) of 6,6-diphenyl-4-(diphenylmethoxy)bicyclo[3.1.0]hex-
3-en-2-one (5e)7 in 200 mL of photolysis grade benzene was irradiated
for 100 min. The solvent was removed in vacuo. The reaction mixture
contained 5,6-diphenyl-3-(diphenylmethoxy)phenol (20e) and 3-oxo-
6,6-diphenyl-4-(diphenylmethyl)hex-5-enoic acid (39) in a ratio of
approximately 45:55 (by NMR). The crude mixture was heated at 130
°C for 3 min and cooled quickly in an ice-water bath. Signals of
acid 39 disappeared in the NMR, and ketone 21 was observed instead.
The crude mixture was chromatographed on two preparative TLC plates
eluted with 10% ether in hexane. Band 1 gave 4.5 mg of a mixture of
unknown compounds. Band 2, 55.6 mg (37.2%), afforded 5,5-diphenyl-
3-(diphenylmethyl)pent-4-en-2-one (21) as an oil. Treatment with
hexane and crystallization from heptane gave 32.3 mg (21.6%) of
colorless crystals, mp 119-121 °C. Band 3 (5.9 mg) gave a mixture
of phenol 20e with unidentified compound. Band 4, 30.1 mg (18.9%),
contained 5,6-diphenyl-3-(diphenylmethoxy)phenol (20e) as an oil.
Treatment with pentane and crystallization from hexane-benzene gave
15.8 mg (9.9%) of colorless crystals, mp 147-148 °C. Band 5 afforded
68.1 mg (30.0%) of starting 6,6-diphenyl-4-(diphenylmethoxy)bicyclo-
[3.1.0]hex-3-en-2-one (5e) with traces of unidentified impurities.
The spectral data for 5,5-diphenyl-3-(diphenylmethyl)pent-4-en-2-
one (21) were the following: 1H NMR (CDCl3, 300 MHz) δ 7.39-
7.36 (m, 3H), 7.25-7.09 (m, 13H), 7.00-6.96 (m, 2H), 6.87-6.86
(m, 2H), 5.91 (d, J ) 10.8 Hz, 1H), 4.45 (d, J ) 10.8 Hz, 1H), 4.15
(dd, J ) 10.8, 10.8 Hz, 1H), 1.94 (s, 3H); MS m/e 402.2027 (calcd for
C30H26O, 402.1985); IR (film) 1712 cm-1. Anal. Calcd for C30H26O:
C, 89.51; H, 6.51. Found: C, 89.56; H, 6.47. The structure assignment
was confirmed by X-ray crystallography (see the Supporting Informa-
tion).
The spectral data for 5,6-diphenyl-3-(diphenylmethoxy)phenol (20e)
were the following: 1H NMR (CDCl3, 300 MHz) δ 7.48-7.42 (m,
4H), 7.40-7.19 (m, 9H), 7.14-7.06 (m, 5H), 7.02-6.95 (m, 2H), 6.70
(d, J ) 2.6 Hz, 1H), 6.63 (d, J ) 2.6 Hz, 1H), 6.28 (s, 1H), 5.08 (s,
1H); MS m/e 428.1768 (calcd for C31H24O2, 428.1777); IR (film) 3200-
3600, 1614, 1581, 1495, 1454, 1419, 1340, 1305, 1194, 1146, 1041
cm-1. Anal. Calcd for C31H24O2: C, 86.89; H, 5.65. Found: C, 86.93;
H, 5.62. The structural assignment was confirmed by X-ray crystal-
lography (see the Supporting Information).
Exploratory Solution Photolysis of 6-exo-(p-Cyanophenyl)-6-
endo-phenylbicyclo[3.1.0]hex-3-en-2-one (7f). A solution of 30 mg
(0.11 mmol) of 6-exo-(p-cyanophenyl)-6-endo-phenylbicyclo[3.1.0]hex-
3-en-2-one (7f) in 17 mL of benzene was irradiated for 35 min to give
a mixture of 6-(p-cyanophenyl)-6-phenylcyclohexa-2,4-dienone (22) and
3-(p-cyanophenyl)-2-phenylphenol (23). The presence of 3-(p-cy-
anophenyl)-2-phenylphenol (23) was confirmed by addition of a
standard sample of 3-(p-cyanophenyl)-2-phenylphenol (23)4d to the
reaction mixture analyzed by NMR (see the Supporting Information).
Solvent was removed in vacuo and the mixture separated on a
preparative TLC plate (10 cm × 20 cm, Machery Nagel No. 81638-25
TLC silica gel) eluted with 30% ether in hexane. Separation was
achieved with loss of 3-(p-cyanophenyl)-2-phenylphenol (23). Band
1 gave 16.1 mg (53.7%) of 6-(p-cyanophenyl)-6-phenylcyclohexa-2,4-
dienone (22) as oil. Band 2 afforded 5.4 mg (18.0%) of 6-exo-(p-
cyanophenyl)-6-endo-phenylbicyclo[3.1.0]hex-3-en-2-one (7f).
× 20 cm, Machery Nagel No. 81638-25 TLC silica gel). Separation
was achieved with loss of 3-(p-cyanophenyl)-2-phenylphenol (23). Band
1 gave 13.8 mg (30.0%) of 6-(p-cyanophenyl)-6-phenylcyclohexa-2,4-
dienone (22) as an oil. Band 2 afforded 6.1 mg (20.3%) of 6-endo-
(p-cyanophenyl)-6-exo-phenylbicyclo[3.1.0]hex-3-en-2-one (7e).
Exploratory Solution Photolysis of 6-exo-(p-Bromophenyl)-4-
methoxy-6-endo-phenylbicyclo[3.1.0]hex-3-en-2-one (24a). A 150
mg (0.42 mmol) portion of 6-exo-(p-bromophenyl)-4-methoxy-6-endo-
phenylbicyclo[3.1.0]hex-3-en-2-one (24a) was irradiated in 250 mL of
benzene for 75 min. The crude mixture contained 6-(p-bromophenyl)-
3-methoxy-6-phenylcyclohexa-2,4-dienone (25), 5-(p-bromophenyl)-
3-methoxy-6-phenylphenol (26), and 6-(p-bromophenyl)-3-methoxy-
5-phenylphenol (27) in a ratio of 64:20:16 (by NMR). Chromatography
on a preparative TLC plate eluted with 10% ether in hexane afforded
11.8 mg (7.9%) of a mixture of phenol 26 and phenol 27 in a ratio of
60:40 (by NMR; see the Supporting Information) in band 1. Band 2
contained 20.9 mg (13.9%) of 6-(p-bromophenyl)-3-methoxy-6-phen-
ylcyclohexa-2,4-dienone (-25) as an oil which solidified upon treatment
with pentane. Crystallization from hexane-methylene chloride gave
12.1 mg (8.1%) of colorless crsytals, mp 119-120 °C. Band 3 afforded
90.1 mg (60.0%) of starting 6-exo-(p-bromophenyl)-4-methoxy-6-endo-
phenylbicyclo[3.1.0]hex-3-en-2-one (24a).
The spectral data for 6-(p-bromophenyl)-3-methoxy-6-phenylcyclo-
hexa-2,4-dienone (25) were the following: 1H NMR (300 MHz, CDCl3)
δ 7.42 (m, 2H), 7.34-7.25 (m, 3H), 7.21-7.15 (m, 2H), 7.09 (m, 2H),
6.71 (d, J ) 10.0 Hz, 1H), 6.27 (dd, J ) 10.0, 2.2 Hz, 1H), 5.52 (d, J
) 2.2 Hz, 1H); MS m/e 356.0235 (calcd for C19H15O2Br, 356.0238);
IR (film) 1652, 1576 cm-1. Anal. Calcd for C19H15O2Br: C, 64.24;
H, 4.26; Br, 22.49. Found: C, 64.19; H, 4.42; Br, 22.44.
Exploratory Solution Photochemistry of 6-endo-(p-Bromophe-
nyl)-4-methoxy-6-exo-phenylbicyclo[3.1.0]hex-3-en-2-one (24b). A
200 mg (0.56 mmol) sample of 6-endo-(p-bromophenyl)-4-methoxy-
6-exo-phenylbicyclo[3.1.0]hex-3-en-2-one (24b) in 200 mL of benzene
was irradiated for 0.5 h. A second identical run was conducted, reaction
mixtures were combined, and solvent was removed in vacuo. The crude
mixture which contained 6-(p-bromophenyl)-3-methoxy-6-phenylcy-
clohexa-2,4-dienone (25), 5-(p-bromophenyl)-3-methoxy-6-phenylphe-
nol (26), and 6-(p-bromophenyl)-3-methoxy-5-phenylphenol (27) in a
ratio of 64:19:17 (by NMR) was chromatographed on two preparative
TLC plates eluted with 10% ether in hexane. Combined bands 1
afforded 13.2 mg (3.3%) of a mixture of phenol 26 and phenol 27 in
a ratio of 58:42 (by NMR; see the Supporting Information). Combined
bands 2 gave 28.0 mg (7.0%) of 6-(p-bromophenyl)-3-methoxy-6-
phenylcyclohexa-2,4-dienone (25) as an oil. Treatment with pentane
and crystallization from hexane-methylene chloride afforded 16.2 mg
(4.1%) of colorless crystals, mp 118-120 °C. Combined bands 3
yielded 324 mg (81.0%) of starting enone 24b.
Solid-State Photolysis of 6,6-Diphenylbicyclo[3.2.1]hex-3-en-2-
one (5a). A 100 mg (0.41 mmol) sample of 6,6-diphenylbicyclo[3.2.1]-
hex-3-en-2-one (5a) was irradiated under standard conditions (see the
General Procedures) for 20 min. The reaction mixture contained,
besides starting enone 5a, 2,3-diphenylphenol (20a) and 3,4-diphe-
nylphenol (13a) in a ratio of 58:42 (by NMR and comparison of NMR
spectra with those of independently prepared4b,8 samples; see the
Supporting Information).
Exploratory Solid-State Photolysis of 4-Methyl-6,6-diphenylbicyclo-
[3.1.0]hex-3-en-2-one (5b). A 40 mg (0.15 mmol) portion of 4-methyl-
6,6-diphenylbicyclo[3.1.0]hex-3-en-2-one (5b) was irradiated under
conditions described in the General Procedures for 10 min through a 5
mm filter solution of 10-3 M sodium metavanadate in 5% sodium
hydroxide. The mixture was chromatographed on preparative TLC plate
eluted with 7% ether in hexane. Band 1 (28.0 mg, 70%) contained
3-methyl-4,5-diphenylphenol (13b). Crystallization from hexane gave
14.1 mg (35%) of colorless crystals, mp 109-110 °C. Band 2 gave
7.0 (17.5%) of starting 4-methyl-6,6-diphenylbicyclo[3.1.0]hex-3-en-
2-one (5b).
Exploratory Solid-State Photolysis of 4-Methoxy-6,6-diphenyl-
bicyclo[3.1.0]hex-3-en-2-one (5c). A 100 mg (0.36 mmol) portion of
crystals of 4-methoxy-6,6-diphenylbicyclo[3.1.0]hex-3-en-2-one (5c)7
was irradiated under conditions described in the General Procedures
for 5 h. The crude mixture was chromatographed on a TLC plate eluted
with 15% ether in hexane. Band 1 (26.6 mg, 26.6%) contained
3-methoxy-5,6-diphenylphenol (20c). Crystallization from hexane gave
The spectral characteristics for 6-(p-cyanophenyl)-6-phenylcyclo-
hexa-2,4-dienone (22) were the following: 1H NMR (300 MHz, CD3-
CN) δ 7.58 (m, 2H), 7.36-7.26 (m, 5H), 7.20-7.10 (m, 3H), 6.68
(ddd, J ) 9.4, 1.7, 0.7 Hz, 1H), 6.45 (ddd, J ) 9.4, 5.9, 0.7 Hz, 1H),
6.11 (m, 1H); MS m/e 271.0987 (calcd for C19H13NO, 271.0997); IR
(film) 3086, 3059, 2919, 2232, 1664, 1631, 1602, 1562, 1493, 1446,
1412, 1369, 1246, 1190, 1134, 1020, 912, 838, 820 cm-1
.
Exploratory Solution Photolysis of 6-endo-(p-Cyanophenyl)-6-
exo-phenylbicyclo[3.1.0]hex-3-en-2-one (7e). A solution of 30 mg
(0.11 mmol) of 6-endo-(p-cyanophenyl)-6-exo-phenylbicyclo[3.1.0]hex-
3-en-2-one (7e) in 17 mL of benzene was irradiated for 35 min to give
a mixture of 6-(p-cyanophenyl)-6-phenylcyclohexa-2,4-dienone (22) and
3-(p-cyanophenyl)-2-phenylphenol (23). The presence of 3-(p-cy-
anophenyl)-2-phenylphenol (23) was confirmed by addition of a
standard sample of 3-(p-cyanophenyl)-2-phenylphenol (23)4d into the
reaction mixture analyzed by NMR. Solvent was removed in vacuo
and the mixture chromatographed on a preparative TLC plate (10 cm

Photochemistry in a Crystalline Cage
J. Am. Chem. Soc., Vol. 119, No. 16, 1997 3689
19.4 mg (19.4%) of colorless crystals, mp 114-116 °C (lit.7 mp 115.5-
117 °C). Band 2 afforded 60.2 mg (60.2%) of starting 4-methoxy-
6,6-diphenylbicyclo[3.1.0]hex-3-en-2-one (5c).
°C. Solvent was evaporated under vacuum. Chromatography on a TLC
preparative silica gel plate eluted with 5% ether in hexane afforded
2.6 mg of a mixture of unidentified compounds in band 1. Band 2
(4.8 mg, 4.3%) gave 5,5-diphenyl-3-(diphenylmethyl)pent-4-en-2-one
(21). Band 3 gave a mixture of 6,6-diphenyl-3-(diphenylmethoxy)-
cyclohexa-2,4-dienone (16e) and starting 6,6-diphenyl-4-(diphen-
ylmethoxy)bicyclo[3.1.0]hex-3-en-2-one (5e). Flash chromatography
on a 2 cm × 30 cm silica gel column eluted with 20% ether in hexane
gave 44.1 mg (37.1%) of 6,6-diphenyl-3-(diphenylmethoxy)cyclohexa-
2,4-dienone (16e) in fraction 1. Crystallization from heptane-
chloroform yielded 32.6 mg (27.4%) of colorless crystals, mp 178-
180 °C. Subsequent elution of the column with 40% ether in hexane
afforded 481 mg (80.2%) of bicyclic enone 5e in fraction 2.
The spectral data for 6,6-diphenyl-3-(diphenylmethoxy)cyclohexa-
2,4-dienone (16e) were the following: 1H NMR (CDCl3, 300 MHz) δ
7.40-7.14 (m, 20H), 6.78 (d, J ) 10.1 Hz, 1H), 6.41 (dd, J ) 10.1,
2.1 Hz, 1H), 6.22 (s, 1H), 5.50 (d, J ) 2.1 Hz, 1H); MS m/e 428.1773
(calcd for C31H24O2 428.1776); IR (film) 1647, 1569, 1226 cm-1. Anal.
Calcd for C31H24O2: C, 86.89; H, 5.65. Found: C, 86.90; H, 5.71.
Exploratory Solid-State Photolysis of 6,6-Diphenyl-4-(diphenyl-
methoxy)bicyclo[3.1.0]hex-3-en-2-one (5e). Final Isomerization by
Melting of Crystals. A 200 mg (0.47 mmol) sample of crystals of
6,6-diphenyl-4-(diphenylmethoxy)bicyclo[3.1.0]hex-3-en-2-one (5e) was
irradiated under conditions described in the General Procedures for 1.5
h with a 400 W Sylvania discharge lamp without external cooling with
water (conversion approximately 10% by NMR). Identical runs were
done 10 times. Individual portions were collected and put into 5 mL
round bottom flasks and heated under an argon atmosphere at 170 °C
until melted. The reaction mixture was quickly cooled in an ice-
water bath. Flash chromatography on a 2.5 cm × 30 cm column eluted
with 15% ether in hexane gave 26.0 mg (6.5%) of 5,5-diphenyl-3-
(diphenylmethyl)pent-4-en-2-one (21) together with minor impurities
in fraction 1. The second fraction afforded 131 mg (31.6%) of 6,6-
diphenyl-3-(diphenylmethoxy)cyclohexa-2,4-dienone (16e). Subsequent
elution of the column with 40% ether in hexane afforded 1.585 g
(79.3%) of starting 6,6-diphenyl-4-(diphenylmethoxy)bicyclo[3.1.0]hex-
3-en-2-one (5e). Fraction 2 was crystallized from heptane-chloroform
to give 99.9 mg (24.1%) of 6,6-diphenyl-3-(diphenylmethoxy)cyclo-
hexa-2,4-dienone (16e), mp 179-180 °C.
Exploratory Solid-State Photolysis of 6-endo(p-Cyanophenyl)-
6-exo-phenylbicyclo[3.1.0]hex-3-en-2-one (7e). Two separate runs of
irradiation of 200 mg (0.74 mmol) of 6-endo-(p-cyanophenyl)-6-exo-
phenylbicyclo[3.1.0]hex-3-en-2-one (7e)4d were conducted. Each sample
was irradiated for 1.5 h under conditions described in the General
Procedures. Both portions were combined and crystallized from
acetonitrile to give 246 mg (61.5%) of starting 6-endo-(p-cyanophenyl)-
6-exo-phenylbicyclo[3.1.0]hex-3-en-2-one (7e) with traces of phenol
30. The acetonitrile solution was evaporated in vacuo and the residue
chromatographed on two TLC silica gel plates eluted with 5% ether in
hexane. Bands 1, 61.6 mg (15.4%), contained a mixture of 2-(p-
cyanophenyl)-3-phenylphenol (30) and 4-(p-cyanophenyl)-3-phenylphe-
nol (31) in a ratio of 10:1 (by NMR). Combined bands 2 afforded
50.0 mg (13%) of starting enone 7e. Crystallization of fraction 1 from
acetonitrile gave 43.0 mg (10.8%) of 2-(p-cyanophenyl)-3-phenylphenol
(30) with traces of 4-(p-cyanophenyl)-3-phenylphenol (31). Evapora-
tion of the acetonitrile solution afforded 18.3 mg (4.6%) of a mixture
of 2-(p-cyanophenyl)-3-phenylphenol (30) and 4-(p-cyanophenyl)-3-
phenylphenol (31) in a ratio of approximately 1:1 (see the Supporting
Information). Crystallization of 2-(p-cyanophenyl)-3-phenylphenol (30)
from acetonitrile gave 34.0 mg (8.5%) of colorless crystals, mp 214-
215 °C.
Exploratory Solid-State Photolysis of 4-tert-Butyl-6,6-diphenyl-
bicyclo[3.2.1]hex-3-en-2-one (5d). A 50 mg (0.17 mmol) portion of
4-tert-butyl-6,6-diphenylbicyclo[3.2.1]hex-3-en-2-one (5d) was placed
in an NMR tube and irradiated for 1.5 h. The same procedure was
repeated 17 times. The overall amount taken into reaction was 850
mg, and conversion reached approximately 5%. Crystals in each NMR
tube were dissolved in 0.2 mL of dry benzene under a dry argon
atmosphere and kept for 2 h. Individual portions were collected, and
the solvent was removed in vacuo. Crude product was crystallized
from hexane. Crystals were filtered off, the filtrate was evaporated,
and the residue was crystallized again from hexane. The combined
crystalline portions gave 640 mg (75.2%) of starting enone 5d. The
filtrate was evaporated. The residue contained, besides starting enone
5d, phenol 20d, phenol 13d, and dienone 16d in a ratio of 42:8:50 (by
NMR). The mixture was separated on a preparative TLC silica gel
plate eluted with 5% ether in hexane. Band 1 (11.7 mg, 1.4%) gave
3-tert-butyl-5,6-diphenylphenol (20d), mp 149-150 °C, from hexane.
Band 2 (13.2 mg, 1.6%) contained 3-tert-butyl-6,6-diphenylcyclohexa-
2,4-dienone (16d) which solidified from pentane, mp 105-107 °C.
Band 3 gave 121 mg (14.2%) of a mixture of starting 4-tert-butyl-6,6-
diphenylbicyclo[3.2.1]hex-3-en-2-one (5d) and 3-tert-butyl-4,5-diphen-
ylphenol (13d) in a ratio of 100:2 (by NMR) with other minor
impurities.
Exploratory Solid-State Photolysis of 6,6-Diphenyl-4-(diphen-
ylmethoxy)bicyclo[3.1.0]hex-3-en-2-one (5e). Final Treatment with
Water. A 200 mg (0.47 mmol) portion of crystals of 6,6-diphenyl-
4-(diphenylmethoxy)bicyclo[3.1.0]hex-3-en-2-one (5e)7 was irradiated
under conditions described in the General Procedures for 1.5 h with a
Hanovia 450 W medium-pressure mercury lamp (conversion ap-
proximately 20% by NMR). The crystals were dissolved in a mixture
of 5 mL of THF and 0.5 mL of water. The mixture was kept for 12
h at 20 °C. Solvent was removed in vacuo. The procedure was
repeated four times. The mixture contained, besides starting enone
5e, 5,5-diphenyl-3-(diphenylmethyl)pent-4-en-2-one (21) and 2-(E)-6,6-
diphenyl-3-(diphenylmethoxy)hexa-2,5-dienoic acid (28) in a ratio of
20:80 (by NMR). The combined crude mixtures were chromatographed
on a 3 cm × 25 cm silica gel column. Elution with 10% ether in
hexane afforded 22.2 mg (10.3%) of 5,5-diphenyl-3-(diphenylmethyl)-
pent-4-en-2-one (21) in fraction 1. Crystallization of ketone 21 from
heptane gave 18.6 mg (8.6%) of colorless crystals, mp 119-121 °C.
Subsequent elution of the column with 30% of ether in hexane afforded
572.8 mg (71.6%) of starting 6,6-diphenyl-4-(diphenylmethoxy)bicyclo-
[3.1.0]hex-3-en-2-one (5e) in fraction 2. Fraction 3 gave 38.2 mg
(16.0%) of 2-(E)-6,6-diphenyl-3-(diphenylmethoxy)hexa-2,5-dienoic
acid (28). Crystallization from heptane-ether gave 25.5 mg (10.7%)
of colorless crystals, mp 151-152 °C.
The spectral data for 2-(E)-6,6-diphenyl-3-(diphenylmethoxy)hexa-
2,5-dienoic acid (28) were the following: 1H NMR (CDCl3, 300 MHz)
δ 7.33-7.18 (m, 20H), 6.16 (t, J ) 7.3 Hz, 1H), 6.06 (s, 1H), 5.04 (s,
1H), 3.69 (d, J ) 7.3 Hz, 2H); MS m/e 402.1985 (M+ - CO2, calcd
for C30H26O 402.1985); IR (film) 1685, 1600 cm-1. Anal. Calcd for
C31H26O3: C, 83.38; H, 5.87. Found: C, 82.99; H, 6.51. The structure
was assigned using X-ray crystallography (see the Supporting Informa-
tion).
Control Experiment of the Stability of 2-(E)-6,6-Diphenyl-3-
(diphenylmethoxy)hexa-2,5-dienoic Acid (28). A 2 mg (4.5 × 10-3
mmol) sample of 2-(E)-6,6-diphenyl-3-(diphenylmethoxy)hexa-2,5-
dienoic acid (28) was dissolved in a mixture of 100 µL of THF and 10
µL of water, and the solution was kept for 24 h in the dark at 20 °C.
Solvent was removed in vacuo, and the NMR spectrum showed no
presence of 5,5-diphenyl-3-(diphenylmethyl)pent-4-en-2-one (21).
Exploratory Solid-State Photolysis of 6,6-Diphenyl-4-(diphenyl-
methoxy)bicyclo[3.1.0]hex-3-en-2-one (5e). Final Isomerization in
Benzene. A 200 mg (0.47 mmol) portion of crystals of 6,6-diphenyl-
4-(diphenylmethoxy)bicyclo[3.1.0]hex-3-en-2-one (5e)7 was irradiated
under conditions described in the General Procedures with a 400 W
Sylvania discharge lamp for 1.5 h without external cooling with water
(conversion approximately 10% by NMR). The same procedure was
repeated three times. The crystals were dissolved in 600 mL of
photolysis grade benzene and kept under dry nitrogen for 1.5 h at 20
The spectral characteristics of 2-(p-cyanophenyl)-3-phenylphenol
(30) were the following: 1H NMR (300 MHz, CD3CN) δ 7.54 (m,
2H), 7.34-7.21 (m, 3H), 7.20-7.12 (m, 3H), 7.07-7.00 (m, 2H), 6.97
(dd, J ) 5.4, 1.2 Hz, 1H), 6.93 (dd, J ) 4.9, 1.1 Hz, 1H); MS m/e
271.0974 (calcd for C19H13NO, 271.0997). Anal. Calcd for C19H13-
NO: C, 84.11; H, 4.83; N, 5.16. Found: C, 84.10; H, 4.68; N, 5.26.
The structure assignment was confirmed by X-ray crystallography (see
the Supporting Information).
Solid-State Photolysis of 6-exo-(p-Cyanophenyl)-6-endo-phenyl-
bicyclo[3.1.0]hex-3-en-2-one (7f). A 100 mg (0.37 mmol) sample of
6-exo-(p-cyanophenyl)-6-endo-phenylbicyclo[3.1.0]hex-3-en-2-one (7f)4d
was divided in five NMR tubes and irradiated under a nitrogen

3690 J. Am. Chem. Soc., Vol. 119, No. 16, 1997
Zimmerman and Sebek
atmosphere in an ice-water bath for 9 h. The crystals were shaken
every 30 min. Reaction mixtures were connected and chromatographed
on a preparative TLC plate eluted with 10% ether in hexane. Band 1
(21.8 mg, 21.8%) contained 3-(p-cyanophenyl)-2-phenylphenol (23),
mp 189-190 °C, from hexane-methylene chloride (lit.4d mp 189.5-
190.5 °C). Band 2 (7.9 mg, 7.9%) contained 3-(p-cyanophenyl)-4-
phenylphenol (29), mp 227-229 °C, from acetonitrile (lit.4d mp 222.8-
225.4 °C). The structure assignment was supported by X-ray
crystallography (see the Supporting Information). Band 3 yielded
starting enone 7f (42.1 mg, 42.1%).
mixture of phenol 27 and phenol 26 in a ratio of 92:8 in fraction 1.
Fraction 2 contained 40.3 mg (2.7%) of a mixture of phenol 27 and
phenol 26 in a ratio of 97:3. Fraction 3 afforded 89.0 mg (5.9%) of
6-(p-bromophenyl)-3-methoxy-5-phenylphenol (27) with traces of
phenol 26. Double crystallization from heptane-chloroform gave 41.8
mg (2.8%) of colorless crystals, mp 130-131 °C. Fraction 4 gave 4.8
mg (0.3%) of an unknown phenol with molecular weight identical with
that of 6-(p-bromophenol)-3-methoxy-5-phenylphenol (27), mp 64-
65 °C, from hexane-ether. Subsequent elution of the column with
40% ether in hexane yielded 730 mg (48.7%) of starting enone 24b in
fraction 5.
The spectral characteristics of 6-(p-bromophenyl)-3-methoxy-5-
phenylphenol (27) were the following: 1H NMR (CDCl3, 250 MHz) δ
7.38 (m, 2H), 7.15-7.20 (m, 3H), 7.03-7.09 (m, 2H), 7.00 (m, 2H),
6.58 (m, 2H), 4.99 (s, 1H), 3.85 (s, 3H); MS m/e 356.0242 (calcd for
C19H15O2Br, 356.0238); IR (film) 2838, 1612, 1579, 1471, 1342, 1304,
1207, 1153, 1055 cm-1. Anal. Calcd for C19H15O2Br: C, 64.24; H,
4.26; Br, 22.49. Found: C, 63.86; H, 4.11; Br, 22.12. The structure
was confirmed by X-ray diffraction (see the Supporting Information).
The spectral characteristics for the unknown phenol were the
following: 1H NMR (CDCl3, 250 MHz) δ 7.29 (m, 2H), 7.19-7.13
(m, 3H), 7.06-6.98 (m, 2H), 6.92 (m, 2H), 6.52 (d, J ) 2.4 Hz, 1H),
6.49 (d, J ) 2.4 Hz, 1H), 5.02 (s, 1H), 3.75 (s, 3H); MS m/e 356.0223
(calcd for C19H15O2Br, 356.0238).
Crystal Packing from the X-ray Crystallography Results. Mini
crystal lattices composing 15-30 molecules were built using SmartPac.6b
MM3 Calculations. Molecular mechanics calculations were per-
formed with MM3(92).11d Reaction intermediates were included in the
“reaction cavity” using flexible or rigid superposition. The central
molecule was than optimized in fixed crystal lattice. Electron positive
and negative centers in zwitterionic intermediates were treated as sp2
carbons.
Flexible and Rigid Superpositions. Geometry analyses were
performed using Macromodel 4.033 and Flexit.34 RMS distances
between corresponding atoms of the starting material in its X-ray
conformation and the appropriate intermediate were evaluated. In
flexible superpositions all non-ring dihedral angles in the molecule of
the intermediate were allowed to alter.
Exploratory Solid-State Photolysis of 6-exo-(p-Bromophenyl)-4-
methoxy-6-endo-phenylbicyclo[3.1.0]hex-3-en-2-one (24a). A 300
mg (0.84 mmol) sample of 6-exo-(p-bromophenyl)-4-methoxy-6-endo-
phenylbicyclo[3.1.0]hex-3-en-2-one (24a) was irradiated under standard
conditions (see the General Procedures) for 7 h. Identical runs were
done five times, and individual portions were connected. The crude
reaction mixture contained 5-(p-bromophenyl)-3-methoxy-6-phenylphe-
nol (26), 6-(p-bromophenyl)-3-methoxy-5-phenylphenol (27), and 5-(p-
bromophenyl)-3-methoxy-4-phenylphenol (33) in a ratio of 72:3:24 (by
NMR). Chromatography on a 2.5 × 75 cm column of deactivated silica
gel eluted with 5% ether in hexane gave 66.0 mg (4.4%) of 5-(p-
bromophenyl)-3-methoxy-6-phenylphenol (26) with traces of phenol
27 in fraction 1. Fraction 2 contained 15.0 mg (1.0%) of a mixture of
phenol 26 and phenol 27 in a ratio of 98:2. Fraction 3 contained 15.0
mg (1.0%) of a mixture of phenol 26 and phenol 27 in a ratio of 91:9.
Subsequent elution of the column with 35% ether in hexane gave 42.8
mg (3.5%) of 5-(p-bromophenyl)-3-methoxy-4-phenylphenol (33) in
fraction 4. Fraction 5 afforded 860 mg (57.3%) of starting 6-exo-(p-
bromophenyl)-4-methoxy-6-endo-phenylbicyclo[3.1.0]hex-3-en-2-
one (24a). Fraction 1 was crystallized twice from heptane to give 47.8
mg (3.2%) of 6-(p-bromophenyl)-3-methoxy-5-phenylphenol (26) as
colorless crystals, mp 170-171 °C. Fraction 4 was crystallized twice
from hexane-methylene chloride to give 18.2 mg (1.2%) of 5-(p-
bromophenyl)-3-methoxy-4-phenylphenol (33) as colorless crystals, mp
144-145 °C.
The spectral characteristics of 5-(p-bromophenyl)-3-methoxy-6-
phenylphenol (26) were the following: 1H NMR (CDCl3, 300 MHz) δ
7.38-7.22 (m, 5H), 7.15-7.06 (m, 2H), 6.94 (m, 2H), 6.61 (d, J )
2.5 Hz, 1H), 6.55 (d, J ) 2.5 Hz, 1H), 5.16 (s, 1H), 3.85 (s, 3H); MS
m/e 356.0242 (calcd for C19H15O2Br, 356.0238); IR (CCl4) 2843, 1616,
1574, 1475, 1425, 1346, 1304, 1205, 1147, 1055 cm-1. Anal. Calcd
for C19H15O2Br: C, 64.24; H, 4.26; Br, 22.49. Found: C, 63.93; H,
4.16. The structure was confirmed by X-ray crystallography (see the
Supporting Information).
The spectral characteristics of 5-(p-bromophenyl)-3-methoxy-4-
phenylphenol (33) were the following: 1H NMR (CDCl3, 300 MHz) δ
7.29-7.12 (m, 5H), 7.00-7.08 (m, 2H), 6.90 (m, 2H), 6.53 (d, J )
2.5 Hz, 1H), 6.45 (d, J ) 2.5 Hz, 1H), 4.83 (s, 1H), 3.74 (s, 3H); MS
m/e 356.0242 (calcd for C19H15O2Br, 356.0238); IR (CCl4) 3575, 3356,
3059, 3016, 2940, 2839, 1598, 1464, 1429, 1346, 1246, 1167, 1136,
1049, 1009, 974 cm-1. Anal. Calcd for C19H15O2Br: C, 64.24; H,
4.26; Br, 22.49. Found: C, 63.84, H, 4.33.
Overlap Calculations of Reaction Intermediates in Their Crystal
Lattice. Intermediates optimized by MM3 were inserted into the
reaction cavity using rigid superposition. CrystLap6b was used to
evaluate their overlap with the surrounding crystal lattice.
Acknowledgment. Support of this research by the National
Science Foundation is acknowledged with appreciation espe-
cially for its concern in supporting basic studies. In addition
we express special appreciation to Dr. Douglas R. Powell for
diffractometry and consultation on X-ray studies.
Supporting Information Available: Summary of X-ray
determinations, tables giving detailed steric energies from MM3,
and a description of the programming used (9 pages). See any
current masthead page for ordering and Internet access
instructions.
Exploratory Solid-State Photolysis of 6-endo-(p-Bromophenyl)-
4-methoxy-6-exo-phenylbicyclo[3.1.0]hex-3-en-2-one (24b). A 250
mg (0.70 mmol) sample of 6-endo-(p-bromophenyl)-4-methoxy-6-exo-
phenylbicyclo[3.1.0]hex-3-en-2-one (24b) was irradiated under standard
conditions (see the General Procedures) for 8 h. The reaction mixture
contained, besides starting enone 24b, 6-(p-bromophenyl)-3-methoxy-
5-phenylphenol (27), 5-(p-bromophenyl)-3-methoxy-6-phenylphenol
(26), and an unknown isomeric phenol in a ratio of 93:2:5 (by NMR).
Identical runs were done six times, and individual portions were
connected. Chromatography on a 2.5 × 60 cm deactivated silica gel
column eluted with 5% ether in hexane gave 30.1 mg (2.0%) of a
JA9630396
(33) Still, W. C.; Mohamadi, F.; Richards, N. G. J.; Guida, W. C.; Lipton,
M.; Liskamp, R.; Chang, G.; Hendrickson, T.; Degunst, F.; Hasel, W.
MacroModel, V3.5; Department of Chemistry, Columbia University, New
York, NY 10027.
(34) Zimmerman, H. E.; St. Clair, J. Flexit. Program to do flexible
superposition and determine RMS variations and related geometric opera-
tions.