Excited- and ground-state versions of the tri-π-methane rearrangement: Mechanistic and exploratory organic photochemistry

Article abstract of DOI:10.1021/jo001601b

The di-π-methane rearrangement with two π-groups bonded to a single carbon leading to π-substituted cyclopropanes is now well established. The present research had as its goal the exploration of molecular systems having three π-moieties attached to an sp³-hybridized atom in a search for a tri-π-methane rearrangement. Indeed, it was found that such systems do rearrange photochemically to afford cyclopentenes. However, it was also established that vinylcyclopropanes ring-expand to cyclopentenes on direct irradiation. Since both three-ring and five-ring photoproducts often are found to be produced, it was important to establish that the observed photochemistry was really the result of a true single-step tri-π-methane rearrangement and not the consequence of two sequential rearrangements, first to form a vinyl cyclopropane which subsequently ring expanded to the cyclopentene. The general situation has three species - A, B, and C - corresponding to tri-π-methane reactant A, vinylcyclopropane photoproduct B, and cyclopentene photoproduct C. Three rate constants are involved, k₁ for A → B, k₂ for A → C, and k₃ for B → C. The kinetics were applied to two examples with provision to avoid differential light absorption; this utilized singlet sensitization. It was determined that direct formation of the cyclopentene photoproduct proceeds more rapidly than the ring-expansion route. In contrast to the di-π-methane rearrangement, the tri-π-methane reaction was found to be preferred by the singlet, while in these sterically congested systems; the triplet led to di-π-methane reactivity. Finally, a ground-state counterpart of the reaction was obtained.

Full text of DOI:10.1021/jo001601b

J . Org. Chem. 2001, 66, 1839-1851
1839
Excited - a n d Gr ou n d -Sta te Ver sion s of th e Tr i-π-m eth a n e
Rea r r a n gem en t: Mech a n istic a n d Exp lor a tor y Or ga n ic
P h otoch em istr y1
Howard E. Zimmerman* and Vladim´ır C´ırkva
Chemistry Department, University of Wisconsin, Madison, Wisconsin 53706
zimmerman@chem.wisc.edu
Received November 10, 2000
The di-π-methane rearrangement with two π-groups bonded to a single carbon leading to
π-substituted cyclopropanes is now well established. The present research had as its goal the
exploration of molecular systems having three π-moieties attached to an sp3-hybridized atom in a
search for a tri-π-methane rearrangement. Indeed, it was found that such systems do rearrange
photochemically to afford cyclopentenes. However, it was also established that vinylcyclopropanes
ring-expand to cyclopentenes on direct irradiation. Since both three-ring and five-ring photoproducts
often are found to be produced, it was important to establish that the observed photochemistry
was really the result of a true single-step tri-π-methane rearrangement and not the consequence
of two sequential rearrangements, first to form a vinyl cyclopropane which subsequently ring
expanded to the cyclopentene. The general situation has three speciessA, B, and Cscorresponding
to tri-π-methane reactant A, vinylcyclopropane photoproduct B, and cyclopentene photoproduct C.
Three rate constants are involved, k1 for A f B, k2 for A f C, and k3 for B f C. The kinetics were
applied to two examples with provision to avoid differential light absorption; this utilized singlet
sensitization. It was determined that direct formation of the cyclopentene photoproduct proceeds
more rapidly than the ring-expansion route. In contrast to the di-π-methane rearrangement, the
tri-π-methane reaction was found to be preferred by the singlet, while in these sterically congested
systems, the triplet led to di-π-methane reactivity. Finally, a ground-state counterpart of the reaction
was obtained.
In tr od u ction
Resu lts
Syn th etic Asp ects. Our investigation began with the
synthesis of a number of tri-π-methane reactants. Scheme
1 presents a convenient route to tris-diphenylvinyl-
methanes. There were several known syntheses7 of the
parent tris-diphenylvinylmethane 3, but we devised the
one in Scheme 1, which proved simplest. This combined
two known types of reactions. Thus, the formation of 3
involves an initial Prins reaction of 1 and 2, anticipated
to lead first to carbinol 7 (Scheme 2). This is in analogy
with the reaction of benzaldehyde with diphenylethyl-
ene.8 Under the acidic conditions, this carbinol was
known9 to react with diphenylethylene to afford the
desired 3.
Organic photochemistry has two main directions. One
is research aimed at discovering new photochemical
reactions, mechanisms, and theory, while the other
involves the study of the photophysics of known pro-
cesses. The present study was initiated with the first
direction in mind. It began with the knowledge that the
di-π-methane rearrangement had been rather thoroughly
studied and was well understood.2 This posed the ques-
tion of whether a counterpart tri-π-methane process was
attainable. Previously, we had observed one example in
a solid-state process,5 but a failure of a tri-π-methane
process in the case of solution photochemistry.6 Thus, the
search for a tri-π-methane rearrangement reaction in
solution presented a special challenge.
(4) (a) See ref 3c. (b) Zimmerman, H. E.; Iwamura, H. J . Am. Chem.
Soc. 1968, 90, 4763-4764. (c) Zimmerman, H. E.; Binkley, R. W.;
Givens, R. S.; Sherwin, M. A.; Grunewald, G. L. J . Am. Chem. Soc.
1969, 91, 3316-3323. (d) Zimmerman, H. E.; Robbins, J . D.; Schantl,
J . J . Am. Chem. Soc. 1969, 91, 5878-5879. (e) Zimmerman, H. E.;
Iwamura, H. J . Am. Chem. Soc. 1970, 92, 2015-2022.
(5) (a) Zimmerman, H. E.; Zuraw, M. J . J . Am. Chem. Soc. 1989,
111, 7974-7989. (b) For a reaction which may be termed a tri-π-
methane rearrangement in utilizing three π-bonds in a different way,
see: Pokkuluri, P. R.; Scheffer, J . R.; Trotter, J . J . Am. Chem. Soc.
1990, 112, 3676-3677.
(6) (a) Mong, G. M.S. Thesis, University of WisconsinsMadison,
1979. (b) Modification of the procedure of Mong, G.6a
(7) (a) Wittig, G.; Kosack, H. J ustus Liebigs Ann. Chem. 1937, 529,
167-184. (b) Ho¨ft, E.; Gru¨ndemann, E.; Gross, H. Liebigs Ann. Chem.
1969, 722, 225-227.
(8) (a) J ones, D. W. J . Chem. Soc. C 1966, 1026-1028. (b) McEwen,
W. E.; Yee, T. T.; Liao, T.-K.; Wolf, A. P. J . Org. Chem. 1967, 32, 1947-
1954.
(1) This is paper 260 of our general series. For paper 259, see:
Zimmerman, H. E.; C´ırkva, V.; J iang, L. Tetrahedron Lett. 2000, 41,
9595-9597.
(2) The mechanism of the rearrangement was first reported in 1967
in the transformation of barrelene3a to semi-bullvalene.4 Although
barrelene had been synthesized earlier3a,b and the rearrangement
observed,3b the first mechanism given was not correct. The correct
mechanism was elucidated in 1967.3c Additionally, we note that in the
correct mechanism, one can construe fifty percent of the semibullvalene
product as arriving from
a
Tri-π-methane mechanism. The case,
however, is somewhat artificial since the two ends of the allylic system
of ”diradical II” are symmetrically disposed to the remaining one-
electron center.
(3) (a) Zimmerman, H. E.; Paufler, R. J . Am. Chem. Soc. 1960, 82,
1514-1515. (b) Zimmerman, H. E.; Grunewald, G. L. J . Am. Chem.
Soc. 1966, 88, 183-184. (c) Zimmerman, H. E.; Binkley, R. W.; Givens,
R. S.; Sherwin, M. A. J . Am. Chem. Soc. 1967, 89, 3932-3933. For a
recent review see Zimmerman, H. E.; Armesto, D. Chem. Rev. 1996,
96, 3065-3112.
(9) Cheminat, B.; Guillaumet, G.; Rambaud, R. Bull. Soc. Chim. Fr.
1972, 3422-3426.
10.1021/jo001601b CCC: $20.00 © 2001 American Chemical Society
Published on Web 02/10/2001

1840 J . Org. Chem., Vol. 66, No. 5, 2001
Zimmerman and C´ırkva
Sch em e 1. Syn th esis of th e Tr i-π-m eth a n es (R-X for 5a Me-I, for 5b P h CH2Br )
Sch em e 2. Rea ction Mech a n ism of th e
trans, di-π-methane rearrangement products. These were
first identified by their characteristic NMR spectra with
an AB quartet deriving from a cyclopropyl methine and
a diphenylvinyl hydrogen and also an unsplit diphenyl-
vinyl hydrogen. The structure of the cis stereoisomer 15a
was established from permanganate oxidation of the
diphenylvinyl side chain to afford the known6 cis-1-
methyl-3,3-diphenylcyclopropane-1,2-dicarboxylic acid 16.
The trans stereoisomer 15b similarly had an NMR
spectrum exhibiting two vinyl hydrogens and one me-
thine coupling with the adjacent vinyl hydrogen. Note
the Experimental Section. The third photoproduct proved
to be more interesting. The NMR spectrum suggested a
substituted five-ring structure, and this was confirmed
by X-ray as 1-methyl-3,3,4,4-tetraphenyl-5-(2,2-diphenyl-
vinyl)-1-cyclopentene (17). This is termed a tri-π-methane
product. Its ratio to the di-π-methane photoproducts
ranged from 1:1 to 1:2 depending on extent of conversion
(vide infra).
Tr i-π-m eth a n e Syn th esis
Sch em e 3. Syn th esis of Diester s 14a a n d 14b
In contrast, acetophenone-sensitized irradiation of the
tri-π-methane reactant 5a led primarily (10:1) to the
stereoisomeric three-ring di-π-methane products 15.
Thus, initially it appeared that, at least in the direct
irradiation, a tri-π-methane rearrangement had been
uncovered. This turns out to be correct. However, as
discussed below, there is evidence that some of the tri-
π-methane product results from a secondary rearrange-
ment of the less dramatic di-π-methane product (i.e., 15).
The tri-π-methane reaction is shown in eq 1.
The tris-diphenylvinylmethane 3 reacted with the
dimsyl anion in DMSO to afford a deep blue10 solution of
the delocalized carbanion 4. This reacted smoothly with
alkyl and benzyl halides to afford the centrally substi-
tuted tri-π-methanes 5a (R ) Me) and 5b (R ) CH2Ph).
Finally, the tri-π-methanes 14a and 14b were desired,
and the synthesis is outlined in Scheme 3.11
Rea r r a n gem en t P h otoch em istr y. Direct irradiation
of tri-π-methane 5a led smoothly to three photoproducts
in a ratio depending on the extent of conversion. Two,
15a and 15b, were easily recognized as ordinary, cis and
(10) Kuhn, R.; Rewicki, D. J ustus Liebigs Ann. Chem. 1965, 690,
50-78.
(11) (a) Central protonation as
a general phenomenon has a
quantum mechanical basis due to maximal electron density.11b,c (b)
Base Catalyzed Rearrangements. In Molecular Rearrangements; Zim-
merman, H. E., DeMayo, P., Eds.; Interscience: New York, 1963;
Chapter 6, pp 345-406 (see especially pp 345-347). (c) Quantum
Mechanics for Organic Chemists; Zimmerman, H. E., Ed.; Academic
Press: New York, 1975; pp 154-155.
In similar fashion, the 3-benzyl tri-π-methane reactant
5b led to both di-π-methane 18 and tri-π-methane 19

Tri-π-methane Rearrangement
J . Org. Chem., Vol. 66, No. 5, 2001 1841
Ta ble 1. P h otop r od u cts Obta in ed on Dir ect Ir r a d ia tion .
Distr ibu tion a t Com p lete Rea ction
Sch em e 4. P h otor ea r r a n gem en t of th e
Dica r bom eth oxy Tr i-π-m eth a n e Rea cta n ts 14a
di-π-methane product
reactant
cis
49
trans
19
tri-π-methane product
methyl
tri-π 5a
benzyl
tri-π 5b
32
31
17
52
photoproducts on direct irradiation; however, in this case
the tri-π-methane product 19 predominated more heavily;
note Table 1. It was also observed that the cis- and trans-
di-π-methane stereoisomers were photochemically inter-
converted approximately 25 times as rapidly as they were
formed. Again as in the methyl example, the aceto-
phenone-sensitized reaction of the tri-π-methane reactant
5b led predominately (75:20) to di-π-methane photoprod-
uct (i.e., 18).
At this point, one would have concluded that in the
direct irradiation there were two reactions proceeding in
parallel, the ordinary di-π-methane rearrangement and
the sought after tri-π-methane rearrangement. However,
it was observed that direct photolysis of the di-π-methane
photoproducts 15 and 18 led to the tri-π-methane photo-
products 17 and 19 as well as undergoing the rapid cis-
trans interconversion (vide supra). Furthermore, the
relative amount of tri-π-methane photoproducts in-
creased with the extent of conversion until at very high
conversions these predominated (eq 2).
a
Cyclopentene 26 is formed only on sensitization.
Also studied were the dicarbomethoxy trienes 14a (R
) Me) and 14b (R ) PhCH2) (Scheme 4). Interestingly,
on direct irradiation only di-π-methane photoproducts
23-25 were formed, while on sensitized irradiation, a
cyclopentene photoproduct 26 was also formed. The ratio
of the three- to five-ring photoproducts was initially in
favor of the di-π-methane photoproduct 24 but at higher
conversions favoring the five-ring photoproduct 26. With
further comment to follow in the Discussion, we merely
note that this five-membered ring does not have a
structure anticipated from a tri-π-methane rearrange-
ment (Scheme 4). Also of interest was the case of the
dicyano tri-π-methane 27, which we studied earlier.5 In
addition to the di-π-methane photoproduct 28 which was
previously observed, on extended sensitized photolysis,
the five-ring photoproduct 29 was obtained; eq 4. The
The parent tri-π-methane 3, lacking a central methyl
or benzyl group, exhibited similar photochemistry but
with the di-π-methane product 21 being formed at low
conversions and with very minor five-ring product 22
being seen only at high conversions. The structure of 21
was established by permanganate oxidation. Equation 3
describes the rearrangement.
mode of formation of this compound along with the
dicarbomethoxy product 26 is considered in the Discus-
sion but as in the case of the dicarbomethoxy series, for
the present, it is sufficient to note, as in the case of the
dicarbomethoxy product 26, that this product is not a tri-
π-methane rearrangement photoproduct.
Kin etic Asp ects. The question has been posed above
whether the cyclopentene photoproducts arise directly via
a tri-π-methane rearrangement or only as a consequence
of a secondary reaction of the di-π-methane (i.e., vinyl-
cyclopropane) photoproducts; see Scheme 5. The situation
is complicated somewhat by the presence of cis and trans
stereoisomers of the cyclopropanes. However, these are
rapidly equilibrated and can be treated kinetically as a
single species. One example of the product variation with
time is given in Scheme 6. The remainder of such kinetic
plots are given in the Supporting Information. We note
differential light absorption by the reacting species due
to three diphenylvinyl groups being present in A and only

1842 J . Org. Chem., Vol. 66, No. 5, 2001
Zimmerman and C´ırkva
Sch em e 5. Alter n a tive Rea ction P a th w a ys
expressions involve k1, k2, and k3, and therefore, it is
necessary to employ an initial guess (e.g., 0.5, 0.5, 0.5)
for these. Then eq 6d in the computer program affords a
better approximation of the k’s. For fitting the theoretical
expression to the experimental data an iterative com-
puter solution was utilized employing our program
ABC_Kinetics.12c At convergence, the rate constants prove
nicely independent of the choice for initial guess values.
The results are given in Table 2.
Lea d in g to Tr i-π-m eth a n e P r od u cts
Gr ou n d -St a t e Tr i-π-m et h a n e R ea r r a n gem en t s.
Although this study primarily focused on excited-state
chemistry, serendipitously two examples of a ground-
state counterpart were encountered in the course of our
synthetic efforts. It was found that boron trifluoride
etherate catalyzed the rearrangement of the tri-π-
methane systems 14a ,b to afford five-membered ring
products 30a ,b. Actually, the rearrangement to 30a was
detected originally in very minor (ca. 3%) yield as a
byproduct of the synthesis of tri-π-methane reactant 14a .
Although these products did not arise in excited-state
processes, they were independently intriguing. This
rearrangement is shown in eq 7, and the reaction
mechanisms are considered in the Discussion. However,
at this point it is sufficient to state that the nature of
the molecular rearrangements in this ground-state chem-
istry is quite different from that encountered in the
photochemical processes.
two in B. Thus, it was of interest to make use of
naphthalene singlet sensitization with the objective of
having a single chromophore absorbing. However, there
is the possibility of differential singlet energy transfer
efficiencies, again giving rise to differential excitation.
Of the two approaches, the direct light absorption seems
preferable since only a known factor of 2:3 is involved.
Kinetics of the type shown in Scheme 5 seem not to have
been solved analytically previously.12a Equation 5 gives
the analytical solution, and the details are given in
Supporting Information.
B ) (k1A0)[e-(k +k )t - e-k t]/(k3 - k1 - k2)
∆Bt ) (∂Bt/∂k1)∆k1 + (∂Bt/∂k2)∆k2 + (∂Bt/∂k3)∆k3
(6a)
(5)
1
2
3
In ter p r eta tive Discu ssion
∆B ) F ∆k
(6c)
(6d)
Th e Tr i-π-m eth a n e Rea r r a n gem en t. The first item
requiring mention is the observation of the desired but
elusive tri-π-methane photoproduct. But as noted in eq
2, there exists a mechanism for conversion of the di-π-
methane photoproducts, e.g., 15 and 18, to afford the tri-
π-methane structures 17 and 19. If this is the only source
of tri-π-methane product, then there would be no real tri-
π-methane rearrangement.
However, the kinetic treatment dissects the indirect
and the direct routes to the tri-π-methane product; see
Scheme 5 where k1 leads to the di-π-methane photoprod-
uct (B in Scheme 5), k2 leads to the tri-π-methane
photoproduct C, and k3 corresponds to the conversion of
initially formed di-π-methane to tri-π-methane product.
Reference to Table 2 shows that k2 heavily predominates
in all cases over k3, demonstrating that most of the five-
membered-ring product truly comes from a direct tri-π-
methane reaction and that the isomerization process
(B f C) proceeds rather slowly.13
∆k ) (F tF )-1F t∆B
Here the ∆Bt term in eq 6a is just the deviation, at a
single time t, of the experimental concentration of B from
the theoretical value, as given by eq 5. Equation 6b
merely gives this variation at all of the reaction times of
interest, and this equation is written more simply as eq
6c. The partial derivatives in eqs 6a and 6b are also
derived in the Supporting Information. Corresponding to
each deviation ∆Bt of a concentration of B at time t, there
is an error in the rate constants k1, k2, and k3. A solution
for the column vector ∆k gives the corrections in the
three rate constants needed to reduce the errors in the
B concentrations over the observation period as given in
the column vector ∆B. The solution for the ∆k vector is
given by eq 6d where F is the matrix of partial derivatives
in eq 6b and F t is the tranpose. However, all of these
One point of interest is the mechanism of conversion
of the di-π-methane to the tri-π-methane products. In this
context, we see that there are two diradicals available
from three-ring opening. Opening of bond a leads to 20,
(12) (a) The solution of these kinetics was not found in a search of
physical chemistry textbooks and the literature. However, elegant
general theory for complex kinetics using an eigenvalue method is
described in ref 12b. and applied to a less complex case. In our hands,
this approach affords the same result as in eq 5 but is cumbersome
and requires special linear combinations of the eigenvectors. Thus, the
method described here seems worthwhile to have in the literature. (b)
Moore, J . W.; Pearson, R. G. Kinetics and Mechanism; Wiley: New
York, 1981. (c) Zimmerman, H. E. Unpublished results. The Supporting
Information gives a flow diagram.
(13) We recognize that the rate constants k1, k2, and k3 may be
treated as relative rates but actually represent the product of quantum
yield and the amount of excitation delivered to each compound.

Tri-π-methane Rearrangement
J . Org. Chem., Vol. 66, No. 5, 2001 1843
Sch em e 6. Va r ia tion of A-C w ith Tim ea
a
Diamonds are for the tri-π-methane reactant, triangles are for di-π-methane, and squares are for tri-π-methane photoproducts: left,
R ) methyl; right, R ) benzyl. Both with naphthalene sensitizer.
Ta ble 2. Rep r esen ta tive Rela tive Ra te Con sta n ts
Sch em e 8. Mech a n ism of th e Tr i-π-m eth a n e
Rea r r a n gem en t in Com p etition w ith th e
observed relative rate
Di-π-m eth a n e P r ocess
constants
tri-π-methane reactant
4-methyl tri-π-methane
sensitizer
none
naphthalene 0.163 0.053 0.004
none 0.223 0.143 0.024
naphthalene 0.099 0.028 0.014
0.018 0.003 0.001
k1
k2
k3
0.102 0.045 0.001
4-benzyl tri-π-methane
4-hydrogen tri-π-methane none
naphthalene 0.102 0.001 0.001
Sch em e 7. Tw o Alter n a tive Dir a d ica ls Ava ila ble
fr om Th r ee-Rin g Op en in g
20 tr a n s) are capable of closing 1,3 to afford the di-π-
methane products (15 and 18).14
Interestingly, the triplet of the tri-π-methane reactants
generated by sensitization exhibit primarily the di-π-
methane rearrangement. This seems likely to result from
selective opening with transoid allylic stereochemistry.
One might anticipate that the transoid diradical would
be preferred by the triplet as a consequence of the greater
odd-electron separation compared with cisoid geometry.
This is an example of exchange integral singlet-triplet
control.15 See Figure 1. Thus, it has been noted that,
where there is multiplicity dependence of photochemical
reaction course, one can consider two types of reactionss
“small K” reactions and “large K” reactions where “K” is
the quantum mechanical exchange integral controlling
the S1-T1 energy gap on the reaction hypersurface. A
number of different reaction types have been empirically
categorized as “small K” or “large K” varieties.15 Reac-
tions involving diradical species lacking polar groups are
of the “large K” type. The generalization has been stated
that triplets prefer large K reactions and singlets prefer
the less delocalized of two diradicals. Alternatively,
scission of bond c affords the more delocalized diradical
31. This diradical (see Scheme 7) is the intermediate in
the rapid cis-trans interconversion but is irrelevant to
the tri-π-methane rearrangement.
The preferred stereochemistry of three-ring opening
leads to the trans-trans diallylic diradical 31, which
cannot close to a five-membered ring. Of the remaining
bonds a and b, breakage of a does lead to the next most
stable diradical with diphenylvinyl and benzhydryl de-
localization as well as having an alkyl group R at a
diradical center. Thus, conversion of the three-membered
ring isomer 15 (or 18) to the tri-π-methane five-ring
product 17 (or 19) product is understood as arising from
fission of bond a followed by bond formation between the
two benzhydryl centers of diradical 20.
In the mechanism for the tri-π-methane rearrangement
we see (see Scheme 8) that there is a conformational
effect. The opening of cyclopropyldicarbinyl diradical 32
can lead to either of two allylic conformations (Scheme
8), with only the cisoid conformer 20 cis (see Scheme 8,
cisoid bond a-b) being able to close to afford the five-
membered ring. The transoid diradical 20 tr a n s (Scheme
8, bond a-b) on such closure would have a trans double
bond in the five-membered ring. Both isomers (20 cis and
(14) The stereochemistry of cyclopropyldicarbinyl diradical 32 is not
presently defined, but as a consequence of free rotation about single
bonds, this is not relevant here.
(15) (a) Zimmerman, H. E.; Armesto, D.; Amezua, M. G.; Gannett,
T. P.; J ohnson, R. P. J . Am. Chem. Soc. 1979, 101, 6367-6383. (b)
Zimmerman, H. E.; Factor, R. E. Tetrahedron 1981, 37, Suppl. 1, 125-
141. (c) Zimmerman, H. E.; Penn, J . H.; J ohnson, M. R. Proc. Natl.
Acad. Sci. U.S.A. 1981, 78, 2021-2025.

1844 J . Org. Chem., Vol. 66, No. 5, 2001
Zimmerman and C´ırkva
Sch em e 9. Mech a n ism of th e BF 3-Ca ta lyzed
Tr i-π-m eth a n e Rea r r a n gem en t
F igu r e 1. Exchange integral control of reactions by multiplic-
ity.
Gr ou n d -Sta te Tr i-π-m eth a n e Rea r r a n gem en t. In-
terestingly, the ground-state counterpart tri-π-methane
rearrangement proceeded by a different mechanism: that
outlined in Scheme 9. The boron trifluoride coordination
with the carbomethoxy carbonyl oxygen is unexceptional.
The bonding to form the cyclopropylcarbinyl cationic
zwitterion 34 as an intermediate merely provides a
mechanism for the 1,2-diphenylvinyl shift leading to the
five-membered ring products 30; aryl and vinyl 1,2-
migrations normally proceed via such bridged species.
This mechanism, however, is a different one than that
involved in the tri-π-methane rearrangement.
small K reactions. Figure 1 makes clear that this is just
a matter of the reacting species selecting the lower energy
of two pathways. Of course, other factors, such as steric
effects, may override the generalization in cases.
Also, an interesting observation is that the tri-π-
methane systems proved perfectly reactive despite the
presence of potential “free-rotors”16 (i.e., the diphenylvinyl
groups). The normal rapid triplet decay due to free-rotor
effects generally seems to diminish with increased steric
congestion as in the present systems where the diphenyl-
vinyl groups have inhibited rotation.
One further observation is that the ratio k2/k3 (see
Scheme 5) diminishes as the group R becomes larger,
thus forcing the benzhydryl odd-electron center trans.
The initial thought is that as R become larger, ring
opening of the cyclopropyldicarbinyl diradical would
afford more of the cisoid allylic moiety, thus favoring k2
and the tri-π-methane route. This clearly is the case
where the “methane carbon” bears only a hydrogen as
in reactant 3 (see eq 3) and where almost exclusively di-
π-methane rearrangement occurs. Referring to Scheme
8, we can see that if R is hydrogen, opening of the
cyclopropyldicarbinyl diradical 32 should prefer the route
leading to the transoid allylic diradical 20 tr a n s for steric
reasons. Also, closure to the three-ring product 15 and
18 does not place four large groups on adjacent carbons.
Con clu sion
The di-π-methane rearrangement has become one of
the useful and widely employed organic reactions to
generate three-membered rings. Now there is a counter-
part tri-π-methane reaction leading to five-membered
ring compounds. The present study has dealt with the
problems of multiplicity control, the presence of two
pathways to the tri-π-methane products, a ground-state
tri-π-methane analogue, and the solution to an interest-
ing kinetic problem.
Exp er im en ta l Section
Gen er a l P r oced u r es. All reactions were performed under
an atmosphere of dry nitrogen. Melting points were deter-
mined in open capillaries with a Meltemp heating block.
Column chromatography was performed on silica gel (Aldrich,
60 Å, 200-400 mesh) mixed with 1% (v/v) of fluorescent
indicator (Sylvania 2282 green phosphor, UV254) and slurry
packed into quartz columns to allow monitoring with a hand-
held UV lamp. Preparative thick-layer chromatography was
carried out with silica gel coated on glass (Sigma, type H, 10-
40 µm, mixed with fluorescent indicator (1%) and gypsum
binder (10%), 50 g of silica gel, and 105 mL of water per plate,
20 × 20 cm). Plates were dried 24 h after preparation at room
temperature. Neutral workup refers to dilution with the
indicated solvent, successive washing with distilled water and
brine, drying over anhydrous magnesium sulfate, and filtering.
Basic workup added an initial saturated NaHCO3 wash after
dilution with water. Acidic workup added an initial 5% HCl
wash after dilution with water. Tetrahydrofuran, diethyl ether
and 1,4-dioxane were purified by storage over potassium
hydroxide, followed by successive distillation under a nitrogen
atmosphere from calcium hydride and sodium benzophenone
ketyl. Dimethyl sulfoxide was distilled from calcium hydride
A final observation is that for the dicarbomethoxy and
dicyano di-π-methane conversions to five-ring products
(i.e., 26 and 29; eq 8), the five-ring products are not those
which arise from a tri-π-methane rearrangement. The
diradical intermediates 36a -c are counterparts of the
diradical 31 (see Scheme 7) utilized in the cis-trans
isomerization discussed for the all hydrocarbon cases.
However, in this instance, the diradical closes to form
the observed five-membered ring products 26a , 26b, and
29, a closure not encountered in absense of the electron-
withdrawing carbomethoxy and cyano groups. One ra-
tionale is that in the hydrocarbon examples it is the
transoid diradical which is formed as a result of lesser
steric interactions while the carbomethoxy and cyano
diradicals are cisoid due to the polar groups and charge
separation being minimized in the cisoid conformation.
(16) (a) Zimmerman, H. E.; Schissel, D. N. J . Org. Chem. 1986, 51,
196-207. (b) Zimmerman, H. E.; Pratt, A. C. J . Am. Chem. Soc. 1970,
92, 1409-1411. (c) Zimmerman, H. E.; Kamm, K. S.; Werthemann, D.
P. J . Am. Chem. Soc. 1975, 97, 3718-3725. (d) Zimmerman, H. E.;
Albrecht, F. X.; Haire, J . J . J . Am. Chem. Soc. 1975, 97, 3726-3740.

Tri-π-methane Rearrangement
J . Org. Chem., Vol. 66, No. 5, 2001 1845
1
prior to use. H NMR spectra were recorded at 300 MHz and
The spectral characteristics were the following: 1H NMR
(CDCl3, 300 MHz) δ 7.40-7.05 (m, 18H, arom), 6.91 (t, 6H, J
) 8 Hz, arom), 6.70 (dd, 6H, J ) 7.5, 1.5 Hz, arom), 6.05 (d,
are reported in ppm downfield from tetramethylsilane. UV
spectra were measured at 25 °C in hexane. The elemental
analyses were performed by the Chemisar Laboratories, Inc.
(Guelph, ON, Canada). The high-resolution electron impact
mass spectra (MS) were run at 150 °C source temperature on
a MS50TC ultrahigh-resolution mass spectrometer manufac-
tured by Kratos, Inc. (Manchester, England). The samples
were run via direct insertion probe and the data collected via
a Kratos DS-55 data acquisition system at the University of
Wisconsin, Biochemistry Department.
1
3H, J ) 10 Hz, 3 × CHd), 4.33 (q, 1H, J ) 10 Hz, CH); H
NMR (benzene-d6, 300 MHz) δ 7.31-6.78 (m, 30H, arom), 6.07
(d, 3H, J ) 10 Hz, CHd), 4.61 (q, 1H, J ) 10 Hz, CH); UV
(hexane) λ(max) ) 268 nm (ꢀ ) 34 560), λ(shoulder) ) 236 nm
(ꢀ ) 33 160), λ ) 300 nm (ꢀ ) 7062); MS m/e 550.2674 (calcd
for C43H34, 550.2661). The structure assignment was confirmed
by X-ray crystallography (see the Supporting Information).
3-Meth yl-3-(2,2-d ip h en ylvin yl)-1,1,5,5-tetr a p h en yl-1,4-
p en ta d ien e (5a ). To a mixture of 0.48 g (20 mmol) of sodium
hydride in 100 mL of anhyd DMSO at 0 °C was added 5.51 g
(10 mmol) of 3-(2,2-diphenylvinyl)-1,1,5,5-tetraphenyl-1,4-pen-
tadiene (3) in 50 mL of anhyd DMSO. After the deep blue
solution was stirred for 6 h at room temperature, 5.68 g (40
mol, 2.49 mL) of methyl iodide was added quickly. The DMSO
solution was diluted with water and then ether extracted.
Concentration of the extracts in vacuo afforded a brown oil
which was filtered through a 5 × 10 cm plug of Florisil and
then through a 5 × 10 cm plug of alumina with dichloro-
methane as eluent. Concentration in vacuo afforded a yellow
oil which was crystallized from cold methanol/ethyl acetate/
ether (2:1:1) to give 2.26 g (40%) of 3-(2,2-diphenylvinyl)-
1,1,5,5-tetraphenyl-1,3-hexadiene (6a ) as colorless plates, mp
80-82 °C (at 60 °C solvated diethyl ether was lost). The
filtrate, on concentration and crystallization from methanol/
dichloromethane (2:1), yielded 2.49 g (44%) of 3-methyl-3-(2,2-
diphenylvinyl)-1,1,5,5-tetraphenyl-1,4-pentadiene (5a ) as col-
orless prisms, mp 115-117 °C.
The spectral characteristics of 3-methyl-3-(2,2-diphenyl-
vinyl)-1,1,5,5-tetraphenyl-1,4-pentadiene (5a ) were the follow-
ing: 1H NMR (CDCl3, 300 MHz) δ 7.30-7.08 (m, 24H, arom),
6.83-6.73 (m, 6H, arom), 5.97 (s, 3H, CHd), 1.13 (s, 3H, CH3);
1H NMR (benzene-d6, 300 MHz) δ 7.26-7.20 (m, 6H, arom),
7.12-6.92 (m, 24H, arom), 6.17 (s, 3H, CHd), 1.28 (s, 3H, CH3);
UV (hexane) λ(max) ) 260 nm (ꢀ ) 31 430), λ ) 300 nm (ꢀ )
3530); MS m/e 564.2805 (calcd for C44H36, 564.2817). Anal.
Calcd for C44H36: C, 93.57; H, 6.43. Found: C, 93.52; H, 6.47.
The structure assignment was confirmed by X-ray crystal-
lography (see the Supporting Information).
Gen er a l P r oced u r e for Kin etic P h otolyses. Kinetic
solution photolyses were carried out in sealed NMR tubes (17
cm of length and 0.5 cm o.d.) in benzene-d6 under nitrogen.
The tube was irradiated in the black-box apparatus.17 Three
filter cells were used (2.0 M NiSO4 in 5% H2SO4, 0.004 M SnCl2
in 15% HCl, and 0.8 M CoSO4 in 5% H2SO4) allowing a 300-
350 nm band-pass. Preparative photolyses were carried out
with an immersion well apparatus and a Hanovia 450 W
medium-pressure mercury lamp equipped with a 5-mm recir-
culating filter solution of 0.020 M copper sulfate. The solution
was purged with deoxygenated and dried nitrogen for 1 h prior
to and during photolysis. Photograde benzene (1 L) was
prepared by washing two 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, and distilling from calcium hydride.
Gen er a l P r oced u r e for Solid -Sta te P h otolyses. Solid-
state photolyses were carried out with a thin layer of crystals
between two quartz plates. The plates were placed to the
cooling wall of the photochemical reactor, and the edges were
tied up with Parafilm tape. The cooling wall was placed into
the reactor flask filled with water-ice mixture. The tempera-
ture of the filter solution and water in the photoreactor was
kept between 15 and 20 °C. Most of the irradiated crystals
was recovered mechanically, and the rest was obtained by
quick washing of the plates with a small amount of appropriate
solvent.
Gen er a l P r oced u r e for X-r a y Cr ysta llogr a p h y An a ly-
sis. X-ray diffraction data were collected on a Bruker-AXS P4
diffractometer with a Smart 1000 CCD area detector for single
crystals of each compound. Lorentz and polarization correc-
tions were applied, and each structure was solved with the
appropriate space group symmetry by direct methods using
SHELXTL18a and SHELXS.18b Hydrogen atom positions were
calculated at idealized positions and included in the structure
factor calculation with fixed isotropic displacement param-
eters. Full-matrix least-squares refinement on F2 was carried
out employing anisotropic displacement parameters for all non-
hydrogen atoms. The coordinates and the Crystallographic
Information Files (cif-files) for all compounds studied by X-ray
crystallography were deposited with the Cambridge Crystal-
lographic Data Centre, 12 Union Rd., Cambridge, CB2 1EZ,
U.K.
The spectral characteristics of 3-(2,2-diphenylvinyl)-1,1,5,5-
tetraphenyl-1,3-hexadiene (6a ) were the following: 1H NMR
(CDCl3, 300 MHz) δ 7.31-6.96 (m, 26H, arom), 6.63-6.55 (m,
2H, arom), 6.42 (t, 1H, J ) 1.47 Hz, dCHCMe), 6.40-6.33 (m,
2H, arom), 6.13 (d, 1H, J ) 1.47 Hz, CHd), 5.79 (d, 1H, J )
1
1.47 Hz, CHd), 1.89 (s, 3H, CH3); H NMR (benzene-d6, 300
MHz) δ 7.25-6.87 (m, 26H, arom), 6.85-6.75 (m, 2H, arom),
6.67-6.57 (m, 2H, arom), 6.47 (t, 1H, J ) 1.5 Hz, CHdCMe),
6.26 (d, 1H, J ) 1.5 Hz, CHd), 6.05 (d, 1H, J ) 1.5 Hz, CH),
1.85 (s, 3H, CH3); UV (hexane) λ(max) ) 302 nm (ꢀ ) 25 629),
λ(shoulder) ) 236 nm (ꢀ ) 26 750), λ ) 325 nm (ꢀ ) 14 120);
MS m/e 564.2852 (calcd for C44H36, 564.2817). The structure
assignment was confirmed by X-ray crystallography (see the
Supporting Information).
3-(2,2-Dip h en ylvin yl)-1,1,5,5-tetr a p h en yl-1,4-p en ta d i-
en e (3). To a solution of 7.22 g (40 mmol) of 1,1-diphenyleth-
ylene and 4.16 g (20 mmol) of 3,3-diphenyl-2-propenal19-20 in
50 mL of anhyd dioxane was added 0.50 mL of concd sulfuric
acid. The solution turned deep blue and then brown and was
heated to reflux for 6 h and then stirred for 12 h at room
temperature. The dioxane was removed in vacuo to afford a
violet oil which was filtered through a 5 × 10 cm plug of Florisil
and then through a 5 × 10 cm plug of Alumina with dichlo-
romethane as eluent. Concentration in vacuo afforded a yellow
oil which was crystallized from dichloromethane/methanol (1:
2) to yield 9.41 g (85%) of 3-(2,2-diphenylvinyl)-1,1,5,5-tet-
raphenyl-1,4-pentadiene (3) as colorless plates, mp 226-228
°C (lit.7b mp 228-230 °C (n-BuOH)).
3-Ben zyl-3-(2,2-d ip h en ylvin yl)-1,1,5,5-tetr a p h en yl-1,4-
p en ta d ien e (5b). To a suspension of 0.24 g (10 mmol) of
sodium hydride in 50 mL of anhyd DMSO was added 2.75 g
(5.0 mmol) of 3-(2,2-diphenylvinyl)-1,1,5,5-tetraphenyl-1,4-
pentadiene (3) in 25 mL of anhyd DMSO. After the deep blue
solution was stirred for 12 h at room temperature, 3.42 g (20
mmol, 2.38 mL) of benzyl bromide was added quickly. The
DMSO was diluted with water and ether extracted. Concen-
tration of the extracts in vacuo afforded a brown oil which was
filtered through a 5 × 10 cm plug of silica gel with dichloro-
methane as eluent. Concentration in vacuo and crystallization
from methanol/dichloromethane (2:1) yielded 2.55 g (80%) of
3-benzyl-3-(2,2-diphenylvinyl)-1,1,5,5-tetraphenyl-1,4-pentadi-
ene (5b) as colorless prisms, mp 182-183 °C (at 90-95 °C
solvated methanol was lost).
(17) Zimmerman, H. E. Mol. Photochem. 1971, 3, 281-292.
(18) (a) Sheldrick, G. M. SHELXTL, Version 5.1, 1997. Bruker AXS,
Inc., Madison, WI 53719. (b) Obtained from Prof. G. Sheldrick,
Go¨ttingen.
(19) Schmidle, C. J .; Barnett, P. G. J . Am. Chem. Soc. 1956, 78, 8,
3209-3210.
(20) Bellassoued, M.; Majidi, A. J . Org. Chem. 1993, 58, 2517-2522.
The spectral characteristics were the following: 1H NMR
(CDCl3, 300 MHz) δ 7.26-6.98 (m, 29H, arom), 6.70-6.62 (m,
1
6H, arom) 5.92 (s, 3H, CHd), 3.00 (s, 2H, CH2Ph); H NMR
(benzene-d6, 300 MHz) δ 7.30-7.24 (m, 2H, arom), 7.19-6.94
(m, 27H, arom), 6.91-6.82 (m, 6H, arom) 6.19 (s, 3H, CHd),

1846 J . Org. Chem., Vol. 66, No. 5, 2001
Zimmerman and C´ırkva
4.26 (s, 3H, CH3OH), 3.17 (s, 2H, CH2Ph); UV (hexane) λ(max)
) 263 nm (ꢀ ) 32 720), λ ) 300 nm (ꢀ ) 3740); MS m/e
organic phases were washed with 1.0 M NaOH (3 × 150 mL),
5% HCl (3 × 150 mL), water (3 × 150 mL) and 150 mL of
saturated NaHCO3. The extracts were dried and filtered
through a 4 × 10 cm plug of Florisil. Concentration in vacuo
and crystallization from hexane (ca. 200 mL) yielded 10.45 g
(84%) of 2-methyl-2-(2,2-diphenylvinyl)-4,4-diphenyl-3-butenal
(13a ) as colorless plates, mp 108-109 °C.
640.3139 (calcd for
51H44O: C, 91.03; H, 6.59. Found: C, 91.41; H, 6.24.
Eth yl 2-(2,2-Dip h en ylvin yl)-4,4-d ip h en yl-3-bu ten oa te
C50H40, 640.3130). Anal. Calcd for
C
(10).6b A solution of 18.63 g (50 mmol) of 1,1,5,5-tetraphenyl-
1,4-pentadiene (9)21,22 in 100 mL of anhyd THF was cooled to
0 °C, and 30 mL (60 mmol) of 2.0 M n-butyllithium in pentane
was added dropwise. After the deep blue solution was stirred
for 30 min at 0 °C, 7.05 g (65 mmol, 6.22 mL) of ethyl
chloroformate was added. The reaction was allowed to stir and
warm to ambient temperature, during which time the color
changed to red violet. Basic workup and concentration in vacuo
afforded a brown-yellow solid. Recrystallization from ethanol
yielded 18.45 g (83%) of ethyl 2-(2,2-diphenylvinyl)-4,4-di-
phenyl-3-butenoate (10) as colorless crystals, mp 94-95 °C.
The spectral characteristics were the following: 1H NMR
(CDCl3, 300 MHz) δ 7.35-7.05 (m, 16H, arom), 7.00-6.91 (m,
4H, arom), 6.19 (d, 2H, J ) 10.2 Hz, CHd), 4.19 (t, 1H, J )
10.2 Hz, CH), 4.15 (q, 2H, J ) 7.3 Hz, CH2OCO), 1.27 (t, 3H,
The spectral characteristics23 were the following: 1H NMR
(CDCl3, 300 MHz) δ 9.02 (s, 1H, CHdO), 7.35-7.03 (m, 20H,
arom), 6.06 (s, 2H, CHd), 1.30 (s, 3H, CH3); UV (hexane) λ-
(max) ) 258 nm (ꢀ ) 26 615), λ ) 300 nm (ꢀ ) 2083); MS m/e
414.1975 (calcd for C31H26O, 414.1984).
Met h yl 2-Ca r bom et h oxy-4-m et h yl-4-(2,2-d ip h en ylvi-
n yl)-6,6-d ip h en yl-2,5-h exa d ien oa te (14a ). To a solution of
50 mL of anhyd THF at 0 °C was added 2.85 g (15 mmol, 1.65
mL) of titanium tetrachloride15b,24 in 4.0 mL of tetrachloro-
methane. To this yellow mixture was added 0.87 g (6.6 mmol,
0.75 mL) of dimethyl malonate and 2.49 g (6.0 mmol) of
2-methyl-2-(2,2-diphenylvinyl)-4,4-diphenyl-3-butenal (13a ) in
10 mL of anhyd THF. The mixture was allowed to stir at 0 °C
for 20 min followed by addition of 2.37 g (30 mmol, 2.42 mL)
of anhyd pyridine. The brown solution was allowed to warm
to room temperature, stirred an additional 13 h, diluted with
30 mL of water, and poured into 100 mL of ether. The aqueous
layer was ether extracted, and the combined organic phases
were washed with water, sodium bicarbonate, and brine, dried,
and concentrated in vacuo leaving 3.20 g of yellow oil.
Chromatography of the crude product on a 3 × 120 cm silica
gel column eluted with 20% ethyl acetate in hexane gave 2.61
g (82%, Rf ) 0.61) of methyl 2-carbomethoxy-4-methyl-4-(2,2-
diphenylvinyl)-6,6-diphenyl-2,5-hexadienoate (14a ) as a vis-
cous oil and 95 mg (3%, Rf ) 0.69) of 1-methyl-3,3-diphenyl-
4,4-dicarbomethoxy-5-(2,2-diphenylvinyl)-1-cyclopentene (30a )
as white crystals, mp 175-177 °C.
The spectral characteristics of methyl 2-carbomethoxy-4-
methyl-4-(2,2-diphenylvinyl)-6,6-diphenyl-2,5-hexadienoate (14a)
were the following: 1H NMR (CDCl3, 300 MHz) δ 7.40-7.12
(m, 16H, arom), 7.08-6.96 (m, 4H, arom), 6.83 (s, 1H, CHd
CCO), 6.00 (s, 2H, CHdCPh), 3.62 (s, 3H, CH3OCO), 3.50 (s,
3H, CH3OCO), 1.25 (s, 3H, CH3); 1H NMR (benzene-d6, 300
MHz) δ 7.28-7.22 (m, 4H, arom), 7.18-6.99 (m, 16H, arom),
7.03 (s, 1H, CHdCCO), 6.19 (s, 2H, CHdCPh), 3.29 (s, 3H,
CH3OCO), 3.25 (s, 3H, CH3OCO), 1.30 (s, 3H, CH3); UV
(hexane) λ(max) ) 256 nm (ꢀ ) 22 150); MS m/e 528.2303
(calcd for C36H32O4, 528.2301).
J
) 7.3 Hz, CH3); MS m/e 444.2102 (calcd for C32H28O2,
444.2089).
E t h yl 2-Met h yl-2-(2,2-d ip h en ylvin yl)-4,4-d ip h en yl-3-
bu ten oa te (11a ).6b To a solution of 8.10 g (80 mmol, 11.21
mL) of diisopropylamine in 300 mL of anhyd THF at -10 °C
(ice-MeOH) was added dropwise 24 mL (48 mmol) of 2.0 M
n-butyllithium in pentane. After the mixture was stirred for
20 min, a solution of 17.78 g (40 mmol) of ethyl 2-(2,2-
diphenylvinyl)-4,4-diphenyl-3-butenoate (10) in 100 mL of
anhyd THF was added dropwise via cannula. The solution
turned brown and was allowed to warm to 10 °C, when 22.71
g (160 mmol, 9.96 mL) of methyl iodide was added. The
resulting solution was stirred 1 h at room temperature before
being quenched with addition of 10% hydrochloric acid. Basic
workup and concentration in vacuo afforded a brown-yellow
solid. Recrystallization from ethanol yielded 15.62 g (85%) of
ethyl 2-methyl-2-(2,2-diphenylvinyl)-4,4-diphenyl-3-butenoate
(11a ) as colorless needles, mp 89-90 °C.
The spectral characteristics were the following: 1H NMR
(CDCl3, 300 MHz) δ 7.28-7.13 (m, 16H, arom), 7.08-7.02 (m,
4H, arom), 6.22 (s, 2H, CHd), 3.67 (q, 2H, J ) 7.3 Hz, CH2-
OCO), 1.40 (s, 3H, CH3), 1.11 (t, 3H, J ) 7.3 Hz, CH3); MS
m/e 458.2254 (calcd for C33H30O2, 458.2246.
2-Met h yl-2-(2,2-d ip h en ylvin yl)-4,4-d ip h en yl-3-b u t en -
ol (12a ).6b To a suspension of 6.08 g (160 mmol) of lithium
aluminum hydride in 200 mL of anhyd THF at 0 °C was added
18.34 g (40 mmol) of ethyl 2-methyl-2-(2,2-diphenylvinyl)-4,4-
diphenyl-3-butenoate (11a ) in 100 mL of anhyd THF. The
reaction mixture immediately turned blue-green and was
allowed to stir for 2 h. The excess of lithium aluminum hydride
was quenched by cautious addition of 3.0 mL of water and then
4.0 mL of 1.0 M NaOH via syringe. The gray solid was filtered
and washed with 200 mL of ether. The filtrate was dried and
concentrated in vacuo afforded a clear oil which was crystal-
lized from ethanol (ca. 50 mL), yielding 14.0 g (84%) of
2-methyl-2-(2,2-diphenylvinyl)-4,4-diphenyl-3-butenol (12a ) as
colorless crystals, mp 120-122 °C.
The spectral characteristics of 1-methyl-3,3-diphenyl-4,4-
dicarbomethoxy-5-(2,2-diphenylvinyl)-1-cyclopentene (30a) were
the following: 1H NMR (CDCl3, 300 MHz) δ 7.80-7.65 (d, 2H,
J ) 8 Hz, arom), 7.50-7.00 (m, 16H, arom), 6.87-6.75 (m,
2H, arom), 5.97 (bs, 1H, CHdCMe), 5.88 (d, 1H, J ) 11 Hz,
CHdCPh), 4.81 (d, 1H, J ) 11 Hz, CH), 3.32 and 3.15 (2 × s,
6H, CH3OCO), 1.91 (s, 3H, CH3); MS m/e 528.2315 (calcd for
C
36H32O4, 528.2301). Anal. Calcd for C36H32O4: C, 81.79; H,
6.10. Found: C, 82.16; H, 6.12. The structure assignment was
confirmed by X-ray crystallography (see the Supporting In-
formation).
The spectral characteristics were the following: 1H NMR
(CDCl3, 300 MHz) δ 7.31-7.11 (m, 16H, arom), 7.07-6.97 (m,
4H, arom), 5.88 (s, 2H, CHd), 3.37 (s, 2H, CH2O), 1.52 (bs,
1H, OH), 0.99 (s, 3H, CH3); MS m/e 416.2130 (calcd for
E t h yl 2-Ben zyl-2-(2,2-d ip h en ylvin yl)-4,4-d ip h en yl-3-
bu ten oa te (11b). To a solution of 12.14 g (120 mmol, 16.82
mL) of diisopropylamine in 400 mL of anhyd THF at -10 °C
(ice-MeOH) was added dropwise 42 mL (84 mmol) of 2.0 M
n-butyllithium in pentane. After the mixture was stirred for
20 min, a solution of 26.68 g (60 mmol) of ethyl 2-(2,2-
diphenylvinyl)-4,4-diphenyl-3-butenoate (10) in 150 mL of
anhyd THF was added dropwise via cannula. The solution
turned brown and was allowed to warm to 10 °C, when 12.0 g
(70 mmol, 8.34 mL) of benzyl bromide was added. The resulting
solution was stirred for 1 h at room temperature before being
quenched with addition of 10% hydrochloric acid. Basic workup
and concentration in vacuo afforded a brown-yellow oil.
Crystallization from ethanol yielded 26.74 g (83%) of ethyl
C
31H28O, 416.2140.
2-Met h yl-2-(2,2-d ip h en ylvin yl)-4,4-d ip h en yl-3-b u t en -
a l (13a ).6b To a solution of 47.5 g (0.60 mol, 48.6 mL) of
pyridine in 300 mL of dichloromethane at 0 °C was added 30.0
g (0.30 mol) of chromium trioxide. After the mixture was
stirred for 45 min, a solution of 12.51 g (0.03 mol) of 2-methyl-
2-(2,2-diphenylvinyl)-4,4-diphenyl-3-butenol (12a ) in 60 mL of
dichloromethane was added dropwise and allowed to stir for
2.5 h. The liquid was decanted and the black residue was
thoroughly washed with 200 mL of dichloromethane. The
(21) Zimmerman, H. E.; Pincock, J . A. J . Am. Chem. Soc. 1973, 95,
2957-2963.
(22) Wittig, G.; Obermann, B. Chem. Ber. 1935, 68, 2214-2218.
(23) Armesto, D.; Ortiz, M. J .; Ramos, A.; Horspool, W. M.; Mayoral,
E. P. J . Org. Chem. 1994, 59, 8115-8124.
(24) Lehnert, W. Tetrahedron 1973, 29, 635-638.

Tri-π-methane Rearrangement
J . Org. Chem., Vol. 66, No. 5, 2001 1847
2-benzyl-2-(2,2-diphenylvinyl)-4,4-diphenyl-3-butenoate (11b)
as colorless needles, mp 117-119 °C.
CHdCCO), 5.94 (s, 2H, CHdCPh), 3.58 (s, 3H, CH3OCO), 3.38
(s, 3H, CH3OCO), 3.08 (s, 2H, CH2Ph); H NMR (benzene-d6,
1
The spectral characteristics were the following: 1H NMR
(CDCl3, 300 MHz) δ 7.27-7.03 (m, 25H, arom), 6.18 (s, 2H,
CHd), 3.42 (q, 2H, J ) 7.1 Hz, CH2OCO), 3.23 (s, 2H, CH2-
Ph), 0.96 (t, 3H, J ) 7.1 Hz, CH3); MS m/e 534.2557 (calcd for
300 MHz) δ 7.28-7.22 (m, 2H, arom), 7.18-6.95 (m, 23H,
arom), 6.98 (s, 1H, CHdCCO), 6.17 (s, 2H, CHdCPh), 3.23 (s,
3H, CH3OCO), 3.22 (s, 3H, CH3OCO), 3.19 (s, 2H, CH2Ph); UV
(hexane) λ(max) ) 254 nm (ꢀ ) 25 400); MS m/e 604.2609
(calcd for C42H36O4, 604.2614). Anal. Calcd for C42H36O4: C,
83.42; H, 6.00. Found: C, 83.49; H, 5.90.
C
39H34O2, 534.2559). Anal. Calcd for C39H34O2: C, 87.61; H,
6.41. Found: C, 87.96; H, 6.34.
2-Ben zyl-2-(2,2-d ip h en ylvin yl)-4,4-d ip h en yl-3-b u t en -
ol (12b). To a suspension of 5.32 g (140 mmol) of lithium
aluminum hydride in 200 mL of anhyd THF at 0 °C was added
17.8 g (33.2 mmol) of ethyl 2-benzyl-2-(2,2-diphenylvinyl)-4,4-
diphenyl-3-butenoate (11b) in 100 mL of anhyd THF. The
reaction mixture immediately turned blue-green and was
stirred for 2 h. The excess lithium aluminum hydride was
quenched by cautious addition of 3.0 mL of water and 5.0 mL
of 1.0 M NaOH via syringe. The gray solid was filtered and
washed with 200 mL of ether. The filtrate was dried, and
concentration in vacuo afforded a clear oil which was crystal-
lized from ethanol (50 mL), yielding 14.61 g (89%) of 2-benzyl-
2-(2,2-diphenylvinyl)-4,4-diphenyl-3-butenol (12b) as a color-
less solid, mp 137-139 °C.
Dir ect Solu tion P h otolysis of 3-Meth yl-3-(2,2-d ip h en -
ylvin yl)-1,1,5,5-tetr a p h en yl-1,4-p en ta d ien e (5a ). A solu-
tion of 150 mg (0.266 mmol) of 3-methyl-3-(2,2-diphenylvinyl)-
1,1,5,5-tetraphenyl-1,4-pentadiene (5a ) in 200 mL of benzene
was irradiated for 15 min. Concentration in vacuo yielded 160
1
mg of yellow oil. H NMR spectroscopic analysis showed 93%
conversion and the composition of the reaction mixture was
52% of cis-cyclopropane 15a , 11% of trans-cyclopropane 15b
and 30% of cyclopentene 17. The mixture was crystallized from
ethyl acetate/diethyl ether and yielded 82 mg of a mixture of
cis-trans isomers 15. Fractional crystallization from methanol/
diethyl ether afforded 55 mg (71%) of cis-1-methyl-3,3-diphen-
yl-1,2-bis(2,2-diphenylvinyl)cyclopropane (15a ) as colorless
thin needles, mp 180-181 °C, and 10 mg (61%) of trans-1-
methyl-3,3-diphenyl-1,2-bis(2,2-diphenylvinyl)cyclopropane (15b)
as colorless prisms, mp 165-166 °C.
The spectral characteristics of cis-1-methyl-3,3-diphenyl-1,2-
bis(2,2-diphenylvinyl)cyclopropane (15a ) were the following:
1H NMR (CDCl3, 300 MHz) δ 7.60-6.90 (m, 30H, arom), 6.30
(s, 1H, CHd), 5.80 (d, 1H, J ) 10.7 Hz, CHd), 2.35 (d, 1H, J
) 10.7 Hz, CH), 0.66 (s, 3H, CH3); UV (hexane) λ(max) ) 262
nm (ꢀ ) 14 167), λ(shoulder) ) 228 nm (ꢀ ) 17 510), λ ) 300
nm (ꢀ ) 5650); MS m/e 564.2810 (calcd for C44H36, 564.2817).
Anal. Calcd for C44H36: C, 93.57; H, 6.43. Found: C, 94.00; H,
6.75.
The spectral characteristics of trans-1-methyl-3,3-diphenyl-
1,2-bis(2,2-diphenylvinyl)cyclopropane (15b) were the follow-
ing: 1H NMR (CDCl3, 300 MHz) δ 7.50-6.80 (m, 30H, arom),
5.81 (s, 1H, CHd), 5.51 (d, 1H, J ) 9.9 Hz, CHd), 2.51 (d, 1H,
J ) 9.9 Hz, CH), 1.42 (s, 3H, CH3); UV (hexane) λ(max) ) 265
nm (ꢀ ) 14850), λ(shoulder) ) 229 nm (ꢀ ) 23 120), λ ) 300
nm (ꢀ ) 5870); MS m/e 564.2808 (calcd for C44H36, 564.2817).
Dir ect Solu tion P h otolysis of 3-Meth yl-3-(2,2-d ip h en -
yl)vin yl-1,1,5,5-tetr a p h en yl-1,4-p en ta d ien e (5a ). A solu-
tion of 150 mg (0.266 mmol) of 3-methyl-3-(2,2-diphenylvinyl)-
1,1,5,5-tetraphenyl-1,4-pentadiene (5a ) in 200 mL of benzene
was irradiated for 1.5 h. Concentration in vacuo yielded 185
mg of yellow oil. 1H NMR spectroscopic analysis showed 100%
conversion and the composition of the reaction mixture was
21% of cis-cyclopropane 15a , 4% of trans-cyclopropane 15b and
75% of cyclopentene 17. The mixture was crystallized from
ethyl acetate/diethyl ether and yielded 32 mg of a mixture of
cis-trans isomers 15. The rest was fractionally crystallized
from methanol/diethyl ether to yield 85 mg (76%) of 1-methyl-
3,3,4,4-tetraphenyl-5-(2,2-diphenylvinyl)-1-cyclopentene (17)
as colorless plates, mp 170-171 °C.
The spectral characteristics were the following: 1H NMR
(CDCl3, 300 MHz) δ 7.28-7.13 (m, 17H, arom), 7.05-6.96 (m,
8H, arom), 5.79 (s, 2H, CHd), 3.12 (d, 2H, J ) 6 Hz, CH2O),
2.98 (s, 2H, CH2Ph), 1.31 (t, 1H, J ) 6 Hz, OH); MS m/e
492.2475 (calcd for
37H32O: C, 90.21; H, 6.55. Found: C, 90.02; H, 6.59.
2-Ben zyl-2-(2,2-d ip h en ylvin yl)-4,4-d ip h en yl-3-b u t en -
C37H32O, 492.2453). Anal. Calcd for
C
a l (13b). To a solution of 44.3 g (0.560 mol, 43.3 mL) of
pyridine in 300 mL of dichloromethane at 0 °C was added 28.0
g (0.280 mol) of chromium trioxide. After the mixture was
stirred for 45 min, a solution of 13.8 g (0.028 mol) of 2-benzyl-
2-(2,2-diphenylvinyl)-4,4-diphenyl-3-butenol (12b) in 100 mL
of dichloromethane was added dropwise and stirred for 2.5 h.
The liquid was then decanted and the black residue was
thoroughly washed with 200 mL of dichloromethane. The
organic phases were then washed with 1.0 M NaOH (3 × 150
mL), 5% HCl (3 × 150 mL), water (3 × 150 mL), and 150 mL
of saturated NaHCO3. The extracts were dried and filtered
through a 4 × 10 cm plug of Florisil. Concentration in vacuo
and crystallization from hexane (ca. 150 mL) yielded 11.6 g
(84%) of 2-benzyl-2-(2,2-diphenylvinyl)-4,4-diphenyl-3-butenal
(13b) as colorless plates, mp 139-141 °C.
The spectral characteristics were the following: 1H NMR
(CDCl3, 300 MHz) δ 8.98 (s, 1H, CHdO), 7.37-6.90 (m, 25H,
arom), 6.03 (s, 2H, CHd), 3.15 (s, 2H, CH2Ph); MS m/e
490.2286 (calcd for
C37H30O, 490.2297). Anal. Calcd for
C
37H30O: C, 90.58; H, 6.16. Found: C, 90.96; H, 6.17. The
structure assignment was confirmed by X-ray crystallography
(see the Supporting Information).
Meth yl 2-Car bom eth oxy-4-ben zyl-4-(2,2-diph en ylvin yl)-
6,6-d ip h en yl-2,5-h exa d ien oa te (14b). To a solution of 80 mL
of anhyd THF at 0 °C was added 2.85 g (15 mmol, 1.65 mL) of
titanium tetrachloride15b,24 in 4.0 mL of tetrachloromethane.
To this yellow mixture was added 0.87 g (6.6 mmol, 0.75 mL)
of dimethyl malonate and 2.94 g (6 mmol) of 2-benzyl-2-(2,2-
diphenylvinyl)-4,4-diphenyl-3-butenal (13b) in 20 mL of anhyd
THF. The mixture was allowed to stir at 0 °C for 20 min
followed by addition of 2.37 g (30 mmol, 2.42 mL) of anhyd
pyridine. The brown solution was allowed to warm to room
temperature, stirred an additional 40 h, diluted with 30 mL
of water and poured into 150 mL of ether. The aqueous layer
was ether extracted and the combined organic phases were
washed with water, sodium bicarbonate, brine, dried and
concentrated in vacuo leaving 3.7 g of yellow oil. Chromatog-
raphy of the crude product on a 5 × 60 cm silica gel column
eluted with 10% diethyl ether in hexane gave 0.29 g (10%, Rf
) 0.45) of starting aldehyde 13b and 2.92 g (Rf ) 0.58) of crude
product as an oil which was crystallized from methanol/acetone
(3:1) to afford 2.72 g (83% at 90% conversion) of methyl
2-carbomethoxy-4-benzyl-4-(2,2-diphenylvinyl)-6,6-diphenyl-
2,5-hexadienoate (14b) as colorless crystals, mp 102-103 °C.
The spectral characteristics were the following: 1H NMR
(CDCl3, 300 MHz) δ 7.51-6.91 (m, 25H, arom), 6.68 (s, 1H,
The spectral characteristics of 1-methyl-3,3,4,4-tetraphenyl-
5-(2,2-diphenylvinyl)-1-cyclopentene (17) were the following:
1H NMR (CDCl3, 300 MHz) δ 7.45-7.02 (m, 20H, arom), 6.91-
6.60 (m, 8H, arom), 6.50 (d, 2H, J ) 8 Hz, arom), 6.38 (m, 1H,
CHdCMe), 5.07 (d, 1H, J ) 11.4 Hz, CHd), 4.68 (dm, 1H, J )
11.4 Hz, CH), 1.98 (t, 3H, J ) 1.1 Hz, CH3); UV (hexane) λ-
(max) ) 258 nm (ꢀ ) 14 972), λ(shoulder) ) 226 nm (ꢀ )
22 320); MS m/e 564.2808 (calcd for C44H36, 564.2817). Anal.
Calcd for C44H36: C, 93.57; H, 6.43. Found: C, 93.38; H, 6.73.
The structure assignment was confirmed by X-ray crystal-
lography (see the Supporting Information).
Kin etics: Dir ect Solu tion P h otolysis of 3-Meth yl-3-(2,2-
d ip h en ylvin yl)-1,1,5,5-tetr a p h en yl-1,4-p en ta d ien e (5a ). A
solution of 10 mg (0.0177 mmol) of 3-methyl-3-(2,2-diphenyl-
vinyl)-1,1,5,5-tetraphenyl-1,4-pentadiene (5a ) in 2.5 mL of
benzene-d6 in a NMR tube was irradiated for varying times
(see the Supporting Information). The course of the reaction
1
was monitored by H NMR spectroscopy.
The spectral characteristics of cis-1-methyl-3,3-diphenyl-1,2-
bis(2,2-diphenylvinyl)cyclopropane (15a ) were the following:

1848 J . Org. Chem., Vol. 66, No. 5, 2001
Zimmerman and C´ırkva
1H NMR (benzene-d6, 300 MHz) δ 7.77-7.69 (m, 2H, arom),
7.56-7.43 (m, 4H, arom), 7.35-7.24 (m, 8H, arom), 7.20-6.80
(m, 16H, arom), 6.68 (s, 1H, CHd), 6.17 (d, 1H, J ) 10.7 Hz,
CHd), 2.69 (d, 1H, J ) 10.7 Hz, CH), 0.90 (s, 3H, CH3).
The spectral characteristics of trans-1-methyl-3,3-diphenyl-
1,2-bis(2,2-diphenylvinyl)cyclopropane (15b) were the follow-
ing: 1H NMR (benzene-d6, 300 MHz) δ 7.50-6.80 (m, 30H,
arom), 5.99 (s, 1H, CHd), 5.79 (d, 1H, J ) 9.9 Hz, CHd), 2.77
(d, 1H, J ) 9.9 Hz, CH), 1.55 (s, 3H, CH3).
The spectral characteristics of 1-methyl-3,3,4,4-tetraphenyl-
5-(2,2-diphenylvinyl)-1-cyclopentene (17) were the following:
1H NMR (benzene-d6, 300 MHz) δ 7.48-7.39 (m, 2H, arom),
7.28-6.65 (m, 28H, arom), 6.31 (dq, 1H, J ) 1.5, 1.1 Hz, CHd
CMe), 5.34 (d, 1H, J ) 11.3 Hz, CHd), 4.92 (ddq, 1H, J ) 11.3,
1.5, 1.1 Hz, CH), 1.82 (t, 3H, J ) 1.1 Hz, CH3).
temperature for 80 h and then filtered through Celite. The
precipitate was washed with 10% HCl and ether. The filtrate
was diluted with ether and after basic workup and concentra-
tion in vacuo afforded 115 mg of yellow oil. The oil was
chromatographed on a 2 × 50 cm silica gel column eluted with
20% ether in hexane to give 12 mg (75%) of colorless oil which
was spectroscopically identical with benzophenone and 27 mg
of colorless oil which crystallized from acetone/hexane (1:3)
yielding 9.4 mg (72%) of cis-1-methyl-3,3-diphenylcyclopro-
pane-1,2-dicarboxylic acid (16) as colorless crystals, mp 170-
172 °C dec (lit.6 mp 168-172 °C dec).
The spectral characteristics of cis-1-methyl-3,3-diphenylcy-
clopropane-1,2-dicarboxylic acid (16) were the following: 1H
NMR (acetone-d6, 300 MHz) δ 12.5 (bs, 2H, CO2H), 7.54-7.44
(m, 4H, arom), 7.39-7.30 (m, 2H, arom), 7.28-7.13 (m, 4H,
arom), 2.83 (s, 1H, CH), 1.28 (s, 3H, CH3).
Dir ect Solu tion P h otolysis of 3-Ben zyl-3-(2,2-d ip h en -
ylvin yl)-1,1,5,5-tetr a p h en yl-1,4-p en ta d ien e (5b). A solu-
tion of 150 mg (0.234 mmol) of 3-benzyl-3-(2,2-diphenylvinyl)-
1,1,5,5-tetraphenyl-1,4-pentadiene (5b) in 200 mL of benzene
was irradiated for 40 min. Concentration in vacuo yielded 160
mg of yellow oil. 1H NMR showed 100% conversion, and the
composition of the reaction mixture was 12% of cis-cyclopro-
pane 18a , 6% of trans-cyclopropane 18b, and 82% of cyclo-
pentene 19. The mixture was crystallized from ethyl acetate/
diethyl ether to give 17 mg of a mixture of cis-trans isomers
18. The rest was fractionally crystallized from acetone/diethyl
ether/methanol (1:1:2) to give 96 mg (78%) of 1-benzyl-3,3,4,4-
tetraphenyl-5-(2,2-diphenylvinyl)-1-cyclopentene (19) as color-
less crystals, mp 228-229 °C (at 95-97 °C solvated methanol
was lost).
Kin etics: Sen sitized (Na p h th a len e) Solu tion P h otoly-
sis of 3-Meth yl-3-(2,2-d ip h en ylvin yl)-1,1,5,5-tetr a p h en yl-
1,4-p en ta d ien e (5a ). A solution of 10 mg (0.0177 mmol) of
3-methyl-3-(2,2-diphenylvinyl)-1,1,5,5-tetraphenyl-1,4-penta-
diene (5a ) and 90 mg (0.71 mmol) of naphthalene in 2.5 mL of
benzene-d6 in a NMR tube was irradiated for varying times
(see the Supporting Information). The course of the reaction
1
was monitored by H NMR spectroscopy.
The spectral characteristics of cis- and trans-cyclopropanes
15 and cyclopentene 17 were the same as in kinetics direct
solution photolysis.
Sen sitized (Acetop h en on e) Solu tion P h otolysis of
3-Met h yl-3-(2,2-d ip h en ylvin yl)-1,1,5,5-t et r a p h en yl-1,4-
p en ta d ien e (5a ). A solution of 150 mg (0.266 mmol) of
3-methyl-3-(2,2-diphenylvinyl)-1,1,5,5-tetraphenyl-1,4-penta-
diene (5a ) and 5.12 g (42.6 mmol, 4.97 mL) of acetophenone
in 200 mL of benzene was irradiated for 10 min. Concentration
The spectral characteristics of 1-benzyl-3,3,4,4-tetraphenyl-
5-(2,2-diphenylvinyl)-1-cyclopentene (19) were the following:
1H NMR (CDCl3, 300 MHz) δ 7.41-6.92 (m, 29H, arom), 6.80-
6.44 (m, 6H, arom), 6.17 (m, 1H, CHdCBz), 5.02 (d, 1H, J )
11.4 Hz, CHd), 4.75 (dm, 1H, J ) 11.4 Hz, CH), 3.55 (s, 2H,
CH2Ph); MS m/e 640.3139 (calcd for C50H40, 640.3130). Anal.
Calcd for C51H44O: C, 91.03; H, 6.59. Found: C, 91.48; H, 6.37.
Kin etics: Dir ect Solu tion P h otolysis of 3-Ben zyl-3-
(2,2-diph en ylvin yl)-1,1,5,5-tetr aph en yl-1,4-pen tadien e (5b).
A solution of 10 mg (0.0156 mmol) of 3-benzyl-3-(2,2-diphen-
ylvinyl)-1,1,5,5-tetraphenyl-1,4-pentadiene (5b) in 2.5 mL of
benzene-d6 in a NMR tube was irradiated for varying times
(see the Supporting Information). The course of the reaction
1
in vacuo yielded 225 mg of yellow oil. H NMR spectroscopic
analysis showed 97% conversion and the composition of the
reaction mixture was 57% of cis-cyclopropane 15a , 26% of
trans-cyclopropane 15b and 14% of cyclopentene 17. The
products were separated by the same way as is described for
direct photolysis.
The spectral characteristics of cis- and trans-cyclopropanes
15 and cyclopentene 17 were the same as in direct solution
photolysis.
Kin etics: Sen sitized (Acetoph en on e) Solu tion P h otoly-
sis of 3-Meth yl-3-(2,2-d ip h en ylvin yl)-1,1,5,5-tetr a p h en yl-
1,4-p en ta d ien e (5a ). A solution of 10 mg (0.0177 mmol) of
3-methyl-3-(2,2-diphenylvinyl)-1,1,5,5-tetraphenyl-1,4-penta-
diene (5a ) and 170 mg (1.42 mmol, 165 µL) of acetophenone
in 2.5 mL of benzene-d6 in a NMR tube was irradiated for
varying times (see the Supporting Information). The course
1
was monitored by H NMR spectroscopy.
The spectral characteristics of cis-1-benzyl-3,3-diphenyl-1,2-
bis(2,2-diphenylvinyl)cyclopropane (18a ) were the following:
1H NMR (benzene-d6, 300 MHz) δ 7.60-6.65 (m, 35H, arom),
6.84 (s, 1H, CHd), 6.23 (d, 1H, J ) 11 Hz, CHd), 3.02 (d, 1H,
J ) 11 Hz, CH), 2.50, 2.42 (2 × d, 2H, J ) 16.5 Hz, CHAHB-
Ph).
The spectral characteristics of trans-1-benzyl-3,3-diphenyl-
1,2-bis(2,2-diphenylvinyl)cyclopropane (18b) were the follow-
ing: 1H NMR (benzene-d6, 300 MHz) δ 7.58-6.66 (m, 35H,
arom), 6.10 (d, 1H, J ) 10.3 Hz, CHd), 5.95 (s, 1H, CHd),
3.47, 3.39 (2 × d, 2H, J ) 15.4 Hz, CHAHBPh), 3.01 (d, 1H, J
) 10.3 Hz, CH).
The spectral characteristics of 1-benzyl-3,3,4,4-tetraphenyl-
5-(2,2-diphenylvinyl)-1-cyclopentene (19) were the following:
1H NMR (benzene-d6, 300 MHz) δ 7.53-7.49 (m, 2H, arom),
7.32-6.64 (m, 33H, arom), 6.32 (m, 1H, CHdCBz), 5.24 (d,
1H, J ) 11.4 Hz, CHd), 5.02 (dm, 1H, J ) 11.4 Hz, CH), 3.42
(s, 2H, CH2Ph).
1
of the reaction was monitored by H NMR spectroscopy.
The spectral characteristics of cis- and trans-cyclopropanes
15 and cyclopentene 17 were the same as in exploratory direct
solution photolysis.
Solid -Sta te P h otolysis of 3-Meth yl-3-(2,2-d ip h en ylvi-
n yl)-1,1,5,5-tetr aph en yl-1,4-pen tadien e (5a). A 50 mg (0.088
mmol) portion of crystals of 3-methyl-3-(2,2-diphenylvinyl)-
1,1,5,5-tetraphenyl-1,4-pentadiene (5a ) was irradiated under
conditions described in the General Procedures for 12 h with
a Hanovia 450 W medium-pressure mercury lamp. Conversion
was 12% and the mixture contained only (as determined by
1H NMR) cyclopropanes 15a /15b in ratio 5:7. The products
were separated by the same way as is described for direct
photolysis.
The spectral characteristics of cis- and trans-cyclopropanes
15 were the same as in direct solution photolysis.
Kin etics: Sen sitized (Na p h th a len e) Solu tion P h otoly-
sis of 3-Ben zyl-3-(2,2-d ip h en ylvin yl)-1,1,5,5-tetr a p h en yl-
1,4-p en ta d ien e (5b). A solution of 10 mg (0.0156 mmol) of
3-benzyl-3-(2,2-diphenylvinyl)-1,1,5,5-tetraphenyl-1,4-pentadi-
ene (5b) and 90 mg (0.71 mmol) of naphthalene in 2.5 mL of
benzene-d6 in a NMR tube was irradiated for varying times
(see the Supporting Information). The course of the reaction
Ch a r a cter iza tion of cis-1-Meth yl-3,3-d ip h en yl-1,2-bis-
(2,2-d ip h en ylvin yl)cyclop r op a n e (15a ).6,25 A solution of 25
mg (0.044 mmol) of cis-1-methyl-3,3-diphenyl-1,2-bis(2,2-
diphenylvinyl)cyclopropane (15a ) in 1.0 mL of benzene was
treated with a solution of 100 mg (0.268 mmol) of dicyclohex-
ano-18-crown-6 and 40.2 mg (0.254 mmol) of potassium per-
manganate in 5.0 mL of benzene and was stirred at room
1
was monitored by H NMR spectroscopy.
The spectral characteristics of cis- and trans-cyclopropanes
18 and cyclopentene 19 were the same as in exploratory direct
solution photolysis.
(25) Zimmerman, H. E.; Welter, T. R. J . Am. Chem. Soc. 1978, 100,
4131-4145.

Tri-π-methane Rearrangement
J . Org. Chem., Vol. 66, No. 5, 2001 1849
Sen sitized (Acetop h en on e) Solu tion P h otolysis of
3-Ben zyl-3-(2,2-d ip h en ylvin yl)-1,1,5,5-t et r a p h en yl-1,4-
p en ta d ien e (5b). A solution of 150 mg (0.234 mmol) of
3-benzyl-3-(2,2-diphenylvinyl)-1,1,5,5-tetraphenyl-1,4-pentadi-
ene (5b) and 5.12 g (42.6 mmol, 4.97 mL) of acetophenone in
200 mL of benzene was irradiated for 5 min. Concentration in
vacuo yielded 200 mg of yellow oil. 1H NMR spectroscopic
analysis showed 95% conversion, and the composition of the
reaction mixture was 52% of cis-cyclopropane 18a , 23% of
trans-cyclopropane 18b, and 20% of cyclopentene 19. The
mixture was crystallized from ethyl acetate/ether to give 95
mg of a mixture of cis-trans isomers 18, then fractional
crystallization from acetone/diethyl ether/methanol (1:1:2)
afforded 53 mg (68%) of cis-1-benzyl-3,3-diphenyl-1,2-bis(2,2-
diphenylvinyl)cyclopropane (18a ) as colorless thin needles, mp
234-235 °C (at 92-93 °C solvated methanol was lost), and
22 mg (63%) of trans-1-benzyl-3,3-diphenyl-1,2-bis(2,2-diphe-
nylvinyl)cyclopropane (18b) as colorless crystals, mp 220-221
°C (at 91-92 °C solvated methanol was lost).
of 10 mg (0.018 mmol) of 3-(2,2-diphenylvinyl)-1,1,5,5-tet-
raphenyl-1,4-pentadiene (3) in 2.5 mL of benzene-d6 in a NMR
tube was irradiated for varying times. The course of the
reaction was monitored by H NMR spectroscopy. At the high
conversion the secondary photoproduct 22 was spectroscopi-
cally observed.
The spectral characteristics of cis-3,3-diphenyl-1,2-bis(2,2-
diphenylvinyl)cyclopropane (21a ) were the following: 1H NMR
(benzene-d6, 300 MHz) δ 7.72 (m, 2H, arom), 7.53-6.75 (m,
28H, arom), 6.34 (6 signals27 of AA′XX′ system, 2H, CHd), 2.87
(6 signals of AA′XX′ system, 2H, CH).
The spectral characteristics of trans-3,3-diphenyl-1,2-bis-
(2,2-diphenylvinyl)cyclopropane (21b) were the following: 1H
NMR (benzene-d6, 300 MHz) δ 7.51-6.73 (m, 30H, arom), 5.53
(6 signals27 of AA′XX′ system, 2H, CHd), 2.99 (6 signals of
AA′XX′ system, 2H, CH).
1
Kin etics: Sen sitized (Na p h th a len e) Solu tion P h otoly-
sis of 3-(2,2-Dip h en ylvin yl)-1,1,5,5-tetr a p h en yl-1,4-p en -
ta d ien e (3). A solution of 10 mg (0.018 mmol) of 3-(2,2-
diphenylvinyl)-1,1,5,5-tetraphenyl-1,4-pentadiene (3) and 90
mg (0.71 mmol) of naphthalene in 2.5 mL of benzene-d6 in a
NMR tube was irradiated for varying times. The course of the
The spectral characteristics of cis-1-benzyl-3,3-diphenyl-1,2-
bis(2,2-diphenylvinyl)cyclopropane (18a ) were the following:
1H NMR (CDCl3, 300 MHz) δ 7.57-6.83 (m, 35H, arom), 6.46
(s, 1H, CHd), 5.86 (d, 1H, J ) 11 Hz, CHd), 2.68 (d, 1H, J )
11 Hz, CH), 2.27, 2.20 (2 × d, 2H, J ) 16.5 Hz, CHAHBPh);
MS m/e 640.3139 (calcd for C50H40, 640.3130). Anal. Calcd for
1
reaction was monitored by H NMR spectroscopy.
The spectral characteristics of cis- and trans-cyclopropanes
21 were the same as in exploratory direct solution photolysis.
Sen sitized (Acetop h en on e) Solu tion P h otolysis of
3-(2,2-Dip h en ylvin yl)-1,1,5,5-t et r a p h en yl-1,4-p en t a d i-
en e (3). A solution of 150 mg (0.272 mmol) of 3-(2,2-diphen-
ylvinyl)-1,1,5,5-tetraphenyl-1,4-pentadiene (3) and 5.12 g (42.6
mmol, 4.97 mL) of acetophenone in 200 mL of benzene was
irradiated for 8 min. Concentration in vacuo yielded 200 mg
of yellow oil. 1H NMR spectroscopic analysis showed 100%
conversion and the composition of the reaction mixture was
55% of cis-cyclopropane 21a and 45% of trans-cyclopropane
21b. Fractional crystallization from methanol/dichloromethane
gave 54 mg (65%) of cis-3,3-diphenyl-1,2-bis(2,2-diphenylvinyl)-
cyclopropane (21a ) as colorless thin needles, mp 228-229 °C,
and 37 mg (55%) of trans-3,3-diphenyl-1,2-bis(2,2-diphenylvi-
nyl)cyclopropane (21b) as colorless crystals, mp 215-216 °C.
The spectral characteristics of cis- and trans-cyclopropanes
21 were the same as in direct solution photolysis.
C
51H44O: C, 91.03; H, 6.59. Found: C, 91.50; H, 6.35.
The spectral characteristics of trans-1-benzyl-3,3-diphenyl-
1,2-bis(2,2-diphenylvinyl)cyclopropane (18b) were the follow-
ing: 1H NMR (CDCl3, 300 MHz) δ 7.46-6.79 (m, 35H, arom),
5.72 (s, 1H, CHd), 5.71 (d, 1H, J ) 10.3 Hz, CHd), 3.25, 2.79
(2 × d, 2H, J ) 15.4 Hz, CHAHBPh), 2.75 (d, 1H, J ) 10.3 Hz,
CH); MS m/e 640.3139 (calcd for C50H40, 640.3130).
Kin etics: Sen sitized (Acetop h en on e) Solu tion P h o-
tolysis of 3-Ben zyl-3-(2,2-d ip h en ylvin yl)-1,1,5,5-tetr a p h e-
n yl-1,4-p en ta d ien e (5b). A solution of 10 mg (0.0156 mmol)
of 3-benzyl-3-(2,2-diphenylvinyl)-1,1,5,5-tetraphenyl-1,4-pen-
tadiene (5b) and 170 mg (1.42 mmol, 165 µL) of acetophenone
in 2.5 mL of benzene-d6 in a NMR tube was irradiated for
varying times (see the Supporting Information). The course
1
of the reaction was monitored by H NMR spectroscopy.
The spectral characteristics of cis- and trans-cyclopropanes
18 and cyclopentene 19 were the same as in exploratory direct
solution photolysis.
Kin etics: Sen sitized (Acetop h en on e) Solu tion P h o-
tolysis of 3-(2,2-Dip h en ylvin yl)-1,1,5,5-tetr a p h en yl-1,4-
p en ta d ien e (3). A solution of 10 mg (0.018 mmol) of 3-(2,2-
diphenylvinyl)-1,1,5,5-tetraphenyl-1,4-pentadiene (3) and 170
mg (1.42 mmol, 165 µL) of acetophenone in 2.5 mL of benzene-
d6 in a NMR tube was irradiated for varying times. The course
Dir ect Solu tion P h otolysis of 3-(2,2-Dip h en ylvin yl)-
1,1,5,5-tetr a p h en yl-1,4-p en ta d ien e (3). A solution of 150 mg
(0.272 mmol) of 3-(2,2-diphenylvinyl)-1,1,5,5-tetraphenyl-1,4-
pentadiene (3) in 200 mL of benzene was irradiated for 15 min.
1
1
of the reaction was monitored by H NMR spectroscopy.
Concentration in vacuo yielded 165 mg of yellow oil. H NMR
The spectral characteristics of cis- and trans-cyclopropanes
21 were the same as in exploratory direct solution photolysis.
Solid -Sta te P h otolysis of 3-(2,2-Dip h en ylvin yl)-1,1,5,5-
tetr a p h en yl-1,4-p en ta d ien e (3). A 50 mg (0.091 mmol)
portion of crystals of 3-(2,2-diphenylvinyl)-1,1,5,5-tetraphenyl-
1,4-pentadiene (3) was irradiated under conditions described
in the General Procedures for 12 h with a Hanovia 450 W
medium-pressure mercury lamp. Conversion was 8% and the
mixture contained (as determined by 1H NMR) cyclopropanes
21a /21b in ratio 5/6. The products were separated by the same
way as is described for direct photolysis.
spectroscopic analysis showed 80% conversion and the com-
position of the reaction mixture was 59% of cis-cyclopropane
21a and 21% of trans-cyclopropane 21b. The starting com-
pound 3 (28 mg) was removed by crystallization of the reaction
mixture from benzene/methanol. The filtrate was fractionally
crystallized from methanol/dichloromethane to give 64 mg
(72%) of cis-3,3-diphenyl-1,2-bis(2,2-diphenylvinyl)cyclopro-
pane (21a ) as colorless thin needles, mp 228-229 °C, and 21
mg (68%) of trans-3,3-diphenyl-1,2-bis(2,2-diphenylvinyl)cy-
clopropane (21b) as colorless needles, mp 215-216 °C.
The spectral characteristics of cis-3,3-diphenyl-1,2-bis(2,2-
diphenylvinyl)cyclopropane (21a ) were the following: 1H NMR
(CDCl3, 300 MHz) δ 7.59-6.95 (m, 30H, arom), 5.90 (6 signals27
of AA′XX′ system, 2H, CHd), 2.57 (6 signals of AA′XX′ system,
2H, CH); MS m/e 550.2646 (calcd for C43H34, 550.2661). Anal.
Calcd for C43H34: C, 93.78; H, 6.22. Found: C, 93.81; H, 6.44.
The spectral characteristics of trans-3,3-diphenyl-1,2-bis-
(2,2-diphenylvinyl)cyclopropane (21b) were the following: 1H
NMR (CDCl3, 300 MHz) δ 7.49-6.95 (m, 30H, arom), 5.22 (6
signals27 of AA′XX′ system, 2H, CHd), 2.59 (6 signals of AA′XX′
system, 2H, CH); MS m/e 550.2646 (calcd for C43H34, 550.2661).
Kin etics: Dir ect Solu tion P h otolysis of 3-(2,2-Dip h en -
ylvin yl)-1,1,5,5-tetr a p h en yl-1,4-p en ta d ien e (3). A solution
The spectral characteristics of cis- and trans-cyclopropanes
21 were the same as in direct solution photolysis.
Ch ar acter ization of cis-3,3-Diph en yl-1,2-bis(2,2-diph en -
ylvin yl)cyclop r op a n e (21a ).25,26 A solution of 25 mg (0.045
mmol) of cis-3,3-diphenyl-1,2-bis(2,2-diphenylvinyl)cyclopro-
pane (21a ) in 1.0 mL of benzene was treated with a solution
of 100 mg (0.268 mmol) of dicyclohexano-18-crown-6 and 40.2
mg (0.254 mmol) of potassium permanganate in 5.0 mL of
benzene, stirred at room temperature for 70 h, and then
filtered through Celite. The precipitate was washed with 10%
HCl and ether. The filtrate was diluted with ether and after
basic workup and concentration in vacuo was obtained 123
mg of yellow oil. The oil was chromatographed on a 2 × 50 cm
silica gel column eluted with 15% ether in hexane and gave
11 mg (67%) of colorless oil which was spectroscopically
identical with benzophenone and 22 mg of colorless oil which
(26) Weber, E.; Hecker, M.; Cso¨regh, I.; Czugler, M. J . Am. Chem.
Soc. 1989, 111, 7866-7872.
(27) Gu¨nther, H. Angew. Chem., Int. Ed. Engl. 1972, 11, 861-874.

1850 J . Org. Chem., Vol. 66, No. 5, 2001
Zimmerman and C´ırkva
crystallized from acetone/water (3:1) yielding 8.3 mg (65%) of
cis-3,3-diphenylcyclopropane-1,2-dicarboxylic acid as colorless
crystals, mp 203-205 °C dec (lit.26 mp 204-206 °C dec).
The spectral characteristics of cis-3,3-diphenylcyclopropane-
1,2-dicarboxylic acid were the following: 1H NMR (acetone-
d6, 300 MHz) δ 11.3 (bs, 2H, CO2H), 7.51-7.43 (m, 4H, arom),
7.36-7.19 (m, 6H, arom), 2.94 (s, 2H, CH).
of cyclopropanes 23a -25a , and band 4 included 45 mg of the
rest of sensitizer.
The spectral characteristics of 1-methyl-3,3,5,5-tetraphenyl-
4-(2,2-dicarbomethoxyvinyl)-1-cyclopentene (26a ) were the fol-
lowing: 1H NMR (CDCl3, 300 MHz) δ 7.52-7.00 (m, 20H,
arom), 6.25 (q, 1H, J ) 1.5 Hz, CHdCMe), 5.88 (d, 1H, J ) 12
Hz, CHdCCO), 5.11 (d, 1H, J ) 12 Hz, CH), 3.54 and 3.38 (2
1
× s, 6H, CH3OCO), 1.57 (d, 3H, J ) 1.5 Hz, CH3); H NMR
Dir ect Solu tion P h otolysis of Meth yl 2-Ca r bom eth oxy-
4-m eth yl-4-(2,2-d ip h en ylvin yl)-6,6-d ip h en yl-2,5-h exa d i-
en oa te (14a ). A solution of 200 mg (0.378 mmol) of methyl
2-carbomethoxy-4-methyl-4-(2,2-diphenylvinyl)-6,6-diphenyl-
2,5-hexadienoate (14a ) in 200 mL of benzene was irradiated
for 10 min. Concentration in vacuo yielded 215 mg of an orange
(benzene-d6, 300 MHz) δ 7.78-7.72 (m, 2H, arom), 7.42-6.82
(m, 18H, arom), 6.25 (d, 1H, J ) 11.8 Hz, CHdCCO), 6.10 (q,
1H, J ) 1.1 Hz, CHdCMe), 5.51 (d, 1H, J ) 11.8 Hz, CH),
3.18, 3.12 (2 × s, 6H, CH3OCO), 1.49 (d, 3H, J ) 1.1 Hz, CH3);
MS m/e 528.2327 (calcd for C36H32O4, 528.2301). Anal. Calcd
for C36H32O4: C, 81.79; H, 6.10. Found: C, 81.47; H, 6.22. The
structure assignment was confirmed by X-ray crystallography
(see the Supporting Information).
1
oil. H NMR spectroscopic analysis showed 100% conversion
and suggested four compounds, 34% of 25a , 20% of 24a , 23%
of 23a tr a n s, and 23% of 23a cis. The mixture was separated
on a preparative silica gel TLC plate eluted with 25% of diethyl
ether in hexane. Band 1 contained 65 mg of 1,1,4,4-tetraphen-
yl-1,3-butadiene as white crystals, mp 201-203 °C (lit.28 mp
203 °C). Band 2 gave 25 mg (54%) of cis-1,1-diphenyl-2-methyl-
2-(2,2-dicarbomethoxyvinyl)-3-(2,2-diphenylvinyl)cyclopro-
pane (23a cis) as a viscous oil, band 3 gave 22 mg (48%) of
trans-1,1-diphenyl-2-methyl-2-(2,2-dicarbomethoxyvinyl)-3-
(2,2-diphenylvinyl)cyclopropane (23a tr a n s) as a viscous oil,
band 4 gave 20 mg (50%) of 1,1-diphenyl-2-methyl-2-(2,2-
diphenylvinyl)-3-(2,2-dicarbomethoxyvinyl)cyclopropane (24a )
as an oil and band 5 contained 42 mg (62%) of 1,1-dicarbo-
methoxy-2-methyl-2,3-bis(2,2-diphenylvinyl)cyclopropane (25a )
as a yellow viscous oil.
The spectral characteristics of 1,1-dicarbomethoxy-2-methyl-
2,3-bis(2,2-diphenylvinyl)cyclopropane (25a ) were the follow-
ing: 1H NMR (CDCl3, 300 MHz) δ 7.52-6.82 (m, 20H, arom),
6.32 (s, 1H, CHdCPh), 5.73 (d, 1H, J ) 8 Hz, CHdCPh), 3.88
and 3.64 (2 × s, 6H, CH3OCO), 2.75 (d, 1H, J ) 8 Hz, CH),
1.37 (s, 3H, CH3); MS m/e 528.2305 (calcd for C36H32O4,
528.2301).
The spectral characteristics of 1,1-diphenyl-2-methyl-2-(2,2-
diphenylvinyl)-3-(2,2-dicarbomethoxyvinyl)cyclopropane (24a )
were the following: 1H NMR (CDCl3, 300 MHz) δ 7.53-6.85
(m, 21H, arom and CHdCCO), 5.89 (s, 1H, CHdCPh), 3.71,
3.70 (2 × s, 6H, CH3OCO), 2.42 (d, 1H, J ) 8 Hz, CH), 1.26 (s,
3H, CH3); MS m/e 528.2303 (calcd for C36H32O4, 528.2301).
The spectral characteristics of trans-1,1-diphenyl-2-methyl-
2-(2,2-dicarbomethoxyvinyl)-3-(2,2-diphenylvinyl)cyclopro-
pane (23a -tr a n s) were the following: 1H NMR (CDCl3, 300
MHz) δ 7.55-6.90 (m, 20H, arom), 6.42 (s, 1H, CHdCCO), 5.97
(d, 1H, J ) 9.5 Hz, CHdCPh), 3.76 and 3.67 (2 × s, 6H, CH3-
OCO), 2.53 (d, 1H, J ) 9.5 Hz, CH), 0.99 (s, 3H, CH3); MS m/e
528.2305 (calcd for C36H32O4, 528.2301).
The spectral characteristics of cis-1,1-diphenyl-2-methyl-2-
(2,2-dicarbomethoxyvinyl)-3-(2,2-diphenylvinyl)cyclopropane
(23a -cis) were the following: 1H NMR (CDCl3, 300 MHz) δ
7.54-6.83 (m, 21H, arom and CHdCCO), 6.02 (d, 1H, J ) 9.5
Hz, CHdCPh), 3.89 and 3.71 (2 × s, 6H, CH3OCO), 2.54 (d,
1H, J ) 9.5 Hz, CH), 0.98 (s, 3H, CH3); MS m/e 528.2303 (calcd
for C36H32O4, 528.2301).
Dir ect Solu tion P h otolysis of Meth yl 2-Ca r bom eth oxy-
4-b en zyl-4-(2,2-d ip h en ylvin yl)-6,6-d ip h en yl-2,5-h exa d i-
en oa te (14b). A solution of 200 mg (0.331 mmol) of methyl
2-carbomethoxy-4-benzyl-4-(2,2-diphenylvinyl)-6,6-diphenyl-
2,5-hexadienoate (14b) in 200 mL of benzene was irradiated
for 8 min. Concentration in vacuo yielded 220 mg of an orange
1
oil. H NMR spectroscopic analysis showed 100% conversion
and suggested four components, 44% of 25b, 18% of 24b, 18%
of 23b-tr a n s, and 20% of 23b-cis. The mixture was separated
on a preparative silica gel TLC plate eluted with 20% of diethyl
ether in hexane. Band 1 contained 45 mg of 1,1,4,4-tetraphen-
yl-1,3-butadiene as white crystals, mp 201-203 °C (lit.28 mp
203 °C). Band 2 gave 27 mg (67%) of cis-1,1-diphenyl-2-benzyl-
2-(2,2-dicarbomethoxyvinyl)-3-(2,2-diphenylvinyl)cyclopro-
pane (23b-cis) as a viscous oil, band 3 gave 23 mg (64%) of
trans-1,1-diphenyl-2-benzyl-2-(2,2-dicarbomethoxyvinyl)-3-(2,2-
diphenylvinyl)cyclopropane (23b-tr a n s) as a viscous oil, band
4 gave 18 mg (50%) of 1,1-diphenyl-2-benzyl-2-(2,2-diphenylvi-
nyl)-3-(2,2-dicarbomethoxyvinyl)cyclopropane (24b) as an oil,
and band 5 contained 56 mg (64%) of 1,1-dicarbomethoxy-2-
benzyl-2,3-bis(2,2-diphenylvinyl)cyclopropane (25b) as a vis-
cous oil.
The spectral characteristics of 1,1-dicarbomethoxy-2-benzyl-
2,3-bis(2,2-diphenylvinyl)cyclopropane (25b) were the follow-
ing: 1H NMR (CDCl3, 300 MHz) δ 7.48-6.81 (m, 25H, arom),
5.92 (s, 1H, CHdCPh), 5.78 (d, 1H, J ) 10 Hz, CHdCPh), 3.31
and 3.08 (2 × s, 6H, CH3OCO), 3.07 (m, 2H, CH2Ph), 2.77 (d,
1H, J ) 10 Hz, CH); MS m/e 604.2610 (calcd for C42H36O4,
604.2614). Anal. Calcd for
Found: C, 83.61; H, 6.09.
C42H36O4: C, 83.42; H, 6.00.
The spectral characteristics of 1,1-diphenyl-2-benzyl-2-(2,2-
diphenylvinyl)-3-(2,2-dicarbomethoxyvinyl)cyclopropane (24b)
were the following: 1H NMR (CDCl3, 300 MHz) δ 7.42-6.85
(m, 26H, arom and CHdCCO), 5.87 (s, 1H, CHdCPh), 3.78
and 3.72 (2 × s, 6H, CH3OCO), 3.48 (m, 2H, CH2Ph), 2.46 (d,
1H, J ) 9 Hz, CH); MS m/e 604.2609 (calcd for C42H36O4,
604.2614). Anal. Calcd for
Found: C, 83.25; H, 5.99.
C42H36O4: C, 83.42; H, 6.00.
The spectral characteristics of trans-1,1-diphenyl-2-benzyl-
2-(2,2-dicarbomethoxyvinyl)-3-(2,2-diphenylvinyl)cyclopro-
pane (23b-tr a n s) were the following: 1H NMR (CDCl3, 300
MHz) δ 7.54-6.89 (m, 25H, arom), 6.27 (s, 1H, CHdCCO), 5.88
(d, 1H, J ) 10 Hz, CHdCPh), 3.81 and 3.63 (2 × s, 6H, CH3-
OCO), 3.17 (m, 2H, CH2Ph), 2.59 (d, 1H, J ) 10 Hz, CH); MS
m/e 604.2610 (calcd for C42H36O4, 604.2614).
The spectral characteristics of cis-1,1-diphenyl-2-benzyl-2-
(2,2-dicarbomethoxyvinyl)-3-(2,2-diphenylvinyl)cyclopropane
(23b-cis) were the following: 1H NMR (CDCl3, 300 MHz) δ
7.55-6.88 (m, 26H, arom and CHdCCO), 5.95 (d, 1H, J ) 11
Hz, CHdCPh), 3.88 and 3.73 (2 × s, 6H, CH3OCO), 3.31 (m,
2H, CH2Ph), 2.51 (d, 1H, J ) 11 Hz, CH); MS m/e 604.2609
(calcd for C42H36O4, 604.2614). Anal. Calcd for C42H36O4: C,
83.42; H, 6.00. Found: C, 83.49; H, 5.91.
Sen sitized Solu tion P h otolysis of Meth yl 2-Ca r bo-
m eth oxy-4-m eth yl-4-(2,2-d ip h en ylvin yl)-6,6-d ip h en yl-2,5-
h exa d ien oa te (14a ). A solution of 100 mg (0.189 mmol) of
methyl 2-carbomethoxy-4-methyl-4-(2,2-diphenylvinyl)-6,6-
diphenyl-2,5-hexadienoate (14a ) and 3.44 g (28.6 mmol) of
acetophenone in 200 mL of benzene was irradiated for 15 min.
Concentration in vacuo yielded 150 mg of an orange-brown
oil. The mixture was separated on a preparative silica gel TLC
plate eluted with 15% diethyl ether in hexane. Band 1 afforded
15 mg of 1,1,4,4-tetraphenyl-1,3-butadiene. Band 2 gave 55
mg (55%) of a viscous oil. 1H NMR analysis suggested a
cyclopentene product. Crystallization from methanol/ether (2:
1) yielded 33 mg (33%) of 1-methyl-3,3,5,5-tetraphenyl-4-(2,2-
dicarbomethoxyvinyl)-1-cyclopentene (26a ) as white crystals,
mp 152-157 °C. Band 3 contained 10 mg (10%) of the mixture
Sen sitized Solu tion P h otolysis of Meth yl 2-Ca r bo-
m eth oxy-4-ben zyl-4-(2,2-d ip h en ylvin yl)-6,6-d ip h en yl-2,5-
h exa d ien oa te (14b). A solution of 100 mg (0.165 mmol) of
methyl 2-carbomethoxy-4-benzyl-4-(2,2-diphenylvinyl)-6,6-
diphenyl-2,5-hexadienoate (14b) and 3.44 g (28.6 mmol) of
acetophenone in 200 mL of benzene was irradiated for 15 min.
(28) Sasaki, K.; Nakao, K.; Kobayashi, Y.; Sakai, M.; Uchino, N.;
Sakakibara, Y.; Takagi, K. Bull. Chem. Soc. J pn. 1993, 66, 2446-2448.

Tri-π-methane Rearrangement
J . Org. Chem., Vol. 66, No. 5, 2001 1851
Concentration in vacuo yielded 185 mg of an orange oil. The
mixture was separated on a preparative silica gel TLC plate
eluted with 10% diethyl ether in hexane. Band 1 contained
13 mg of 1,1,4,4-tetraphenyl-1,3-butadiene. Band 2 gave 66
mg (66%) of a yellow oil. 1H NMR analysis suggested a
cyclopentene product. Crystallization from acetone/ether/
methanol (1:1:2) yielded 43 mg (43%) of-1-benzyl-3,3,5,5,-
tetraphenyl-4-(2,2-dicarbomethoxyvinyl-1-cyclopentene (26b)
as white crystals, mp 203-204 °C. Band 3 contained 14 mg
(14%) of the mixture of cyclopropanes 23b-25b, and band 4
included 55 mg of the rest of sensitizer.
The spectral characteristics of 1-benzyl-3,3,5,5-tetraphenyl-
4-(2,2-dicarbomethoxyvinyl)-1-cyclopentene (26b) were the
following: 1H NMR (CDCl3, 300 MHz) δ 7.40-6.82 (m, 25H,
arom), 5.90 (d, 1H, J ) 11.4 Hz, CHdCCO), 5.87 (m, 1H, CHd
CBz), 5.15 (d, 1H, J ) 11.4 Hz, CH), 3.53, 3.37 (2 × s, 6H,
CH3OCO), 3.33, 2.69 (2 × dd, 2H, J ) 16.9, 1.5 Hz, CHAHB-
Ph); 1H NMR (benzene-d6, 300 MHz) δ 7.67-7.54 (m, 4H,
arom), 7.52-7.45 (m, 2H, arom), 7.30-6.76 (m, 19H, arom),
6.29 (d, 1H, J ) 11.8 Hz, CHdCCO), 6.10 (dd, 1H, J ) 1.5,
1.1 Hz, CHdCBz), 5.60 (d, 1H, J ) 11.8 Hz, CH), 3.28 (dd,
1H, J ) 17, 1.5 Hz, CH2Ph), 3.20, 3.13 (2 × s, 6H, CH3OCO),
2.80 (dd, 1H, J ) 17, 1.1 Hz, CH2Ph); MS m/e 604.2609 (calcd
for C42H36O4, 604.2614). Anal. Calcd for C42H36O4: C, 83.42;
H, 6.00. Found: C, 83.53; H, 6.02.
Solid -Sta te P h otolysis of Meth yl 2-Ca r bom eth oxy-4-
b e n zyl-4-(2,2-d ip h e n ylvin yl)-6,6-d ip h e n yl-2,5-h e xa d i-
en oa t e (14b). A 50 mg (0.083 mmol) portion of crystals of
methyl 2-carbomethoxy-4-benzyl-4-(2,2-diphenylvinyl)-6,6-
diphenyl-2,5-hexadienoate (14b) was irradiated under condi-
tions described in the General Procedures for 10 h with a
Hanovia 450 W medium-pressure mercury lamp. The reaction
mixture contained only starting compound (after the analysis
with 1H NMR).
Sen sitized Solu tion P h otolysis of 2-Cya n o-4-m eth yl-
4-(2,2-d ip h en ylvin yl)-6,6-d ip h en yl-2,5-h exa d ien en it r ile
(27).5a A solution of 100 mg (0.216 mmol) of 2-cyano-4-methyl-
4-(2,2-diphenylvinyl)-6,6-diphenyl-2,5-hexadienenitrile (27) and
3.4 g (28.6 mmol) of acetophenone in 200 mL of benzene was
irradiated for 2 h. Concentration in vacuo yielded 155 mg of
pale yellow oil. Chromatography of the crude material on a 3
× 15 cm silica gel column eluted with 20% ether in hexane
gave 50 mg of yellow oil which was crystallized from methanol/
dichloromethane (3:1) to give 45 mg (45%) of 1-methyl-3,3,5,5-
tetraphenyl-4-(2,2-dicyanovinyl)-1-cyclopentene (29) as white
needles, mp 206-208 °C.
yellow oil which was crystallized from ether/methanol (1:2) to
afford 85 mg (81%) of 1-methyl-3,3-diphenyl-4,4-dicarbomethoxy-
5-(2,2-diphenylvinyl)-1-cyclopentene (30a ) as colorless crystals,
mp 175-177 °C.
The spectral characteristics were the following: 1H NMR
(benzene-d6, 300 MHz) δ 7.98-7.85 (m, 2H, arom), 7.51-6.75
(m, 18H, arom), 6.21 (d, 1H, J ) 10.6 Hz, CHdCPh), 5.88 (m,
1H, CHdCMe), 5.14 (dm, 1H, J ) 10.6 Hz, CH), 3.05 and 2.99
(2 × s, 6H, CH3OCO), 1.85 (bs, 3H, CH3); UV (hexane) λ(max)
) 254 nm (ꢀ ) 17 140), λ(shoulder) ) 226 nm (ꢀ ) 18 090), λ
) 300 nm (ꢀ ) 2); MS m/e 528.2315 (calcd for C36H32O4,
528.2301). Anal. Calcd for
C36H32O4: C, 81.79; H, 6.10.
Found: C, 82.16; H, 6.12. The structure assignment was
confirmed by X-ray crystallography (see the Supporting In-
formation).
1-Methyl-3,3-diphenyl-4,4-dicarbomethoxy-5-(2,2-diphen-
ylvin yl)-1-cyclop en ten e (30a ) (BF 3‚Et2O Meth od ). To 3.0
mL of anhyd diethyl ether was added 28 mg (0.20 mmol) of
boron trifluoride etherate and then 106 mg (0.20 mmol) of
methyl 2-carbomethoxy-4-methyl-4-(2,2-diphenylvinyl)-6,6-
diphenyl-2,5-hexadienoate (14a ) in 1.0 mL of anhyd ether. The
mixture was stirred at room temperature for 24 h. The crude
reaction mixture was filtered through a 0.5 × 2 cm plug of
silica gel eluted with ether, dried and concentrated in vacuo
leaving 95 mg of yellow oil. Chromatography of the crude
product on a 3 × 15 cm silica gel column eluted with 30% ether
in hexane gave 90 mg of yellow oil which was crystallized from
ether/methanol (1:2) to afford 80 mg (76%) of 1-methyl-3,3-
diphenyl-4,4-dicarbomethoxy-5-(2,2-diphenylvinyl)-1-cyclopen-
tene (30a ) as colorless crystals, mp 175-177 °C, identical with
material obtained from the TiCl4 method (vide supra).
1-Benzyl-3,3-diphenyl-4,4-dicarbomethoxy-5-(2,2-diphen-
ylvin yl)-1-cyclop en ten e (30b). To 3.0 mL of anhyd diethyl
ether was added 28 mg (0.20 mmol) of boron trifluoride
etherate and then 121 mg (0.20 mmol) of methyl 2-carbo-
methoxy-4-benzyl-4-(2,2-diphenylvinyl)-6,6-diphenyl-2,5-hexadi-
enoate (14b) in 1.0 mL of anhyd ether. The mixture was stirred
at room temperature for 24 h. The crude reaction mixture was
filtered through a 0.5 × 2 cm plug of silica gel eluted with
ether, dried and concentrated in vacuo leaving 110 mg of oil.
Chromatography of the crude product on a 3 × 15 cm silica
gel column eluted with 30% ether in hexane gave 105 mg of
yellow oil which was crystallized from ether/methanol (1:2) to
afford 98 mg (81%) of 1-benzyl-3,3-diphenyl-4,4-dicarbomethoxy-
5-(2,2-diphenylvinyl)-1-cyclopentene (30b) as colorless crystals,
mp 226-228 °C.
The spectral characteristics were the following: 1H NMR
(CDCl3, 300 MHz) δ 7.70-7.55 (d, 2H, J ) 7 Hz, arom), 7.53-
7.15 (m, 18H, arom), 7.05-6.93 (m, 3H, arom), 6.90-6.73 (m,
2H, arom), 6.50 (dt, 1H, J ) 2.6, 2.0 Hz, CHdCBz), 5.62 (d,
1H, J ) 10 Hz, CHdCPh), 4.81 (ddt, 1H, J ) 10, 2.6, 2.0 Hz,
CH), 3.95 (m, 2H, CH2Ph), 3.77 and 2.89 (2 × s, 6H, CH3OCO);
MS m/e 604.2609 (calcd for C42H36O4, 604.2614). Anal. Calcd
for C42H36O4: C, 83.42; H, 6.00. Found: C, 83.76; H, 6.09.
The spectral characteristics of 1-methyl-3,3,5,5-tetraphenyl-
4-(2,2-dicyanovinyl)-1-cyclopentene (29) were the following: 1H
NMR (CDCl3, 300 MHz) δ 7.51-7.38 (m, 4H, arom), 7.37-
7.03 (m, 16H, arom), 6.21 (q, 1H, J ) 1.5 Hz, CHdCMe), 6.01
(d, 1H, J ) 12 Hz, CHdCCN), 5.33 (d, 1H, J ) 12 Hz, CH),
1.65 (d, 3H, J ) 1.5 Hz, CH3); 1H NMR (benzene-d6, 300 MHz)
δ 7.51 (m, 4H, arom), 7.35-6.74 (m, 16H, arom), 5.92 (d, 1H,
J ) 12.1 Hz, CHdCCN), 5.86 (q, 1H, J ) 1.5 Hz, CHdCMe),
5.61 (d, 1H, J ) 12.1 Hz, CH), 1.40 (d, 3H, J ) 1.5 Hz, CH3);
MS m/e 462.2103 (calcd for C34H26N2, 462.2095).
1-Methyl-3,3-diphenyl-4,4-dicarbomethoxy-5-(2,2-diphen-
ylvin yl)-1-cyclop en ten e (30a ). (TiCl4 method) To 3.0 mL of
anhyd THF at 0 °C was added 89 mg (0.47 mmol, 52 µL) of
titanium tetrachloride24 in 0.125 mL of tetrachloromethane.
To this yellow mixture was added 100 mg (0.189 mmol) of
methyl 2-carbomethoxy-4-methyl-4-(2,2-diphenylvinyl)-6,6-
diphenyl-2,5-hexadienoate (14a ) in 0.50 mL of anhyd THF. The
mixture was stirred at 0 °C for 20 min followed by addition of
79 mg (1.0 mmol, 81 µL) of anhyd pyridine. The yellow solution
was allowed to warm to room temperature, followed by
addition of 3.4 mg (0.189 mmol, 3.4 µL) of water and stirred
an additional 24 h. The crude reaction mixture was filtered
through a 0.5 × 2 cm silica gel column eluted with ether, dried
and concentrated in vacuo leaving 0.11 g of yellow oil.
Chromatography of the crude product on a 3 × 20 cm silica
gel column eluted with 30% ether in hexane gave 100 mg of
Ack n ow led gm en t. Support of this research by the
National Science Foundation is gratefully acknowledged
with special appreciation for its support of basic re-
search. Also, we wish to acknowledge helpful discussions
with and advice from Drs. Douglas Powell and Igor V.
Alabugin regarding X-ray diffractometry. We are also
pleased to acknowledge Departmental NSF grants CHE-
9310428 and CHE-9709005 supporting X-ray facilities
and NSF CHE-9208463, NIH 1 510 RRO 8391-01
supporting NMR.
Su p p or tin g In for m a tion Ava ila ble: Programming de-
tails and further kinetic results are given. This material is
available free of charge via the Internet at http://pubs.acs.org.
J O001601B