Photocycloaddition of Cyanonaphthalenes to 1,3-Cyclohexadiene

Article abstract of DOI:10.1021/jo971748b

To prevent secondary processes due to facile thermal reaction, low-temperature irradiations of cyanonaphthalenes and 1,3-cyclohexadiene through a Pyrex filter were conducted. Along with the identification of the products, the results of the triplet-sensitized photoreaction of the irradiated mixture, low-temperature ¹H NMR study of the irradiated mixture, and the Cope rearrangement reaction of some products suggested that the primary major products are the corresponding exo-[4 + 4] adducts fused at 1,4 position of the naphthalene skeleton and the syn-[2 + 2] adducts fused at 1,2 position. The formations of the primary products in these singlet-state photocycloaddition reactions were interpreted by primary and secondary orbital interactions. A rationalization for the previous results on the photoreactions at room temperature was also provided.

Full text of DOI:10.1021/jo971748b

1
212
J . Org. Chem. 1998, 63, 1212-1216
P h otocycloa d d ition of Cya n on a p h th a len es to 1,3-Cycloh exa d ien e
Taehee Noh,* Daekyun Kim, and Yong-J ae Kim
Department of Chemistry Education, Seoul National University, Seoul, 151-742, Korea
Received September 18, 1997
To prevent secondary processes due to facile thermal reaction, low-temperature irradiations of
cyanonaphthalenes and 1,3-cyclohexadiene through a Pyrex filter were conducted. Along with the
identification of the products, the results of the triplet-sensitized photoreaction of the irradiated
1
mixture, low-temperature H NMR study of the irradiated mixture, and the Cope rearrangement
reaction of some products suggested that the primary major products are the corresponding exo-[4
+
4] adducts fused at 1,4 position of the naphthalene skeleton and the syn-[2 + 2] adducts fused
at 1,2 position. The formations of the primary products in these singlet-state photocycloaddition
reactions were interpreted by primary and secondary orbital interactions. A rationalization for
the previous results on the photoreactions at room temperature was also provided.
In tr od u ction
The stereoselectivity in many Diels-Alder reactions
Sch em e 1. Dir ect Ir r a d ia tion s of
Cya n on a p h th a len es a n d CHD
has been explained reasonably by the secondary orbital
interaction between the HOMO and the LUMO of sub-
strates.1 Although the consideration of the frontier
molecular orbitals does not establish the magnitude of
stabilizing interaction, it has been shown to be quite
useful and predictable in many circumstances. On the
other hand, there have been relatively few examples of
the photoreactions that exhibit stereoselectivity due to
the secondary orbital interaction between the LUMO’s.2
Moreover, several photocycloaddition reactions exhibit
the stereoselectivity which contradicts the prediction
based on the LUMO-LUMO interaction between the
substrates. These include the ambient-temperature pho-
toreactions of 1-cyanonaphthalene (1-CN) with furan3
and of 1-CN and 2-cyanonaphthalene (2-CN) with 1,3-
cyclohexadiene (CHD).4 In the latter cases, the explana-
tion provided for this consequence was that the cyano
group lowers the energy of the naphthalene orbitals and
the interaction between the HOMO of CHD and the
LUMO of cyanonaphthalenes becomes significant. On
the other hand, the photocycloaddition of 1-CN to furan
has been reinvestigated at low temperature in order to
Resu lts a n d Discu ssion
A dichloromethane solution of 1-CN and CHD at -78
C was irradiated through a Pyrex filter for 4 h, and two
2 + 2] adducts (1 and 2) were isolated from the reaction
°
[
5
prevent secondary processes, in which the stereoselec-
mixture in 13% and 58% yields, respectively (Scheme 1).
The mass spectrum (CI) of 1 exhibits the molecular ion
peak at 234 (M + 1), indicating a 1:1 adduct of 1-CN and
CHD. The structural assignment for 1 was made par-
ticularly by the analysis of its NMR spectra. Four
aromatic protons, four olefinic protons (δ 5.6-6.3), and
tivity is consistent with the prediction based on the
secondary orbital interaction. We have therefore rein-
vestigated the photocycloaddition reactions of 1-CN and
2
-CN with CHD at low temperature.
1
three cyclobutyl protons (δ 3.2-3.9) in its H NMR
(1) (a) Gilchrist, T. L.; Storr, R. C. Organic reactions and orbital
symmetry, 2nd ed.; Cambridge University Press: Cambridge, 1979. (b)
Machiguchi, T.; Hasegawa, T.; Ishii, Y.; Yamabe, S.; Minato, T. J . Am.
Chem. Soc. 1993, 115, 11536. (c) Chiacchio, U.; Casuscelli, F.; Corsaro,
A.; Rescifina, A.; Romeo, G.; Uccella, N. Tetrahedron 1994, 50, 6671.
spectrum indicated that the cyclohexadiene ring was
fused to the 1,2 position of 1-CN. Strong coupling
between the peaks at δ 3.62 (H-7) and 5.60 (H-6) in its
COSY spectrum (Figure 1) indicated that the double bond
in cyclohexene ring was not at the 3,4 position but at the
5,6 position. The strong 1,2 coupling (J ) 9.4 Hz)
between H-7 and H-8 in decoupling experiment, the
NOE’s with the cyclobutyl protons in its NOESY spec-
trum, and the singlet mechanism of the photocycloaddi-
(
d) Apeloig, Y.; Matzner, E. J . Am. Chem. Soc. 1995, 117, 5375. (e)
J ursic, B. S. J . Org. Chem. 1997, 62, 3046.
2) (a) Yang, N. C.; Masnovi, J .; Chiang, W.; Wang, T.; Shou, H.;
(
Yang, D.-D. H. Tetrahedron 1981, 37, 3285. (b) Yang, N. C.; Gan, H.;
Kim, S. S.; Masnovi, J . M.; Rafalko, P. W.; Ezell, E. F.; Lenz, G. R.
Tetrahedron Lett. 1990, 31, 3825.
(
3) (a) Pac, C.; Sugioka, T.; Sakurai, H. Chem. Lett. 1972, 39 and
6
67. (b) Kan, K.; Kai, Y.; Yasuoka, N.; Kasai, N. Bull. Chem. Soc.
J pn. 1979, 52, 2, 1634. (c) Sakurai, H.; Pac, C. Mem. Inst. Sci. Ind.
Res. Osaka Univ. 1980, 37, 59.
4
tion suggested the product to be a syn-[2 + 2] adduct.
Similar spectroscopic data analyses of 2 showed that
CHD was fused to the 3,4 position of 1-CN.
(
(
4) Albini, A.; Fasani, E.; Giavarini, F. J . Org. Chem. 1988, 53, 5601.
5) Noh, T.; Kim, D. Tetrahedron Lett. 1996, 37, 9329.
S0022-3263(97)01748-9 CCC: $15.00 © 1998 American Chemical Society
Published on Web 01/27/1998

Photocycloaddition of Cyanonaphthalenes
J . Org. Chem., Vol. 63, No. 4, 1998 1213
3
F igu r e 1. COSY spectrum of 1 in CDCl .
F igu r e 2. Orbital interactions between naphthalenes and
CHD.
Sch em e 2. Tr ip let-Sen sitized Rea ction s of th e
Ir r a d ia ted Mixtu r es of Cya n on a p h th a len es a n d
CHD
The products in the irradiation at -78 °C seem to be
different from those at 17 °C. It was reported by Albini
and co-workers that the products identified in the room-
temperature irradiation of 1-CN and CHD were 7, 8, and
9
in 53%, 6%, and 7% yields, respectively.4 The product
distribution was also reported to be the same in the
irradiation at 0 °C. However, their structural assignment
for the major product (7), which was based on the absence
of a cage adduct in the irradiation of the adduct in the
presence of xanthone, turned out to be wrong, and its
correct structure was assigned to be 1 (Figure 1). The
products in the case of 2-CN and CHD in cyclohexane at
1
7 °C were reported to be 10 and 11 in 53% and 12%
4
yields. However, the products of the photoreaction at
78 °C in dichloromethane were found to be similar to
-
A dichloromethane solution of 2-CN and CHD at -78
those at room temperature in cyclohexane. The correct
assignment for their major product was again turned out
to be 3.
°
C was irradiated through a Pyrex filter for 5 h to give a
complex mixture, from which three products were par-
tially separated (Scheme 1). Two of these were 1:1
adducts of 2-CN and CHD as revealed by their MS
spectra. The other product was a 1:2 adduct of 2-CN and
1
CHD. Its H NMR, COSY, and NOESY spectra allowed
the assignment for 5. Analysis of the spectroscopic data
of the 1:1 adducts indicated that the major product was
the exo-[4 + 4] adduct (4) and the minor product was
the syn-[2 + 2] adduct (3) fused to the 1,2 position of the
naphthalene skeleton. Strong coupling between the
peaks at δ 3.69 and 5.68 in the COSY spectrum of 3
allowed the assignment for the position of the double
1
bonds. From the H NMR spectrum of the direct irradi-
ated mixture of 2-CN and CHD, the ratio of 3, 4, and 5
was estimated to be 21:68:11. The isolated yield of 3 was
1
6% on the basis of the consumed 2-CN. The structure
of the major product (4) was further confirmed by the
The product distribution in the singlet-state reaction
was previously explained by the dominant interaction
between the HOMO of CHD and the LUMO of 1-CN due
triplet sensitization of the irradiated mixture of 2-CN and
6
CHD (Scheme 2). These consecutive photoreactions gave
the corresponding cage adduct (6) in 39% yield as well
as 3 (16%), 4 (22%), and 5 (23%). Interestingly, the yield
of 5 was increased probably by the triplet-sensitized
photocycloaddition. In the triplet sensitization of the
purified 4, the isolated yield of 6 was 79%.
4
to the lowering of the 1-CN orbitals by the cyano group.
However, a simple calculation showed that the lowering
of the LUMO of 1-CN was not significant to change the
7
components of the primary interaction (Figure 2). Con-
(
6) Kimura, M.; Kura, H.; Nukada, K.; Okamoto, H.; Satake, K.;
(7) The energies and the coefficients were calculated by the Extended
HMO after geometry optimization.
Morosawa, S. J . Chem. Soc., Perkin Trans. 1 1988, 3307.

1
214 J . Org. Chem., Vol. 63, No. 4, 1998
Noh et al.
sidering the primary and secondary orbital interactions
between the LUMO’s of 1-CN and CHD, the major
product is still expected to be the exo-[4 + 4] intermediate
(12). By considering the primary orbital interaction, the
formation of [2 + 2] adduct (e.g., 1) is expected to be more
favorable than the formation of 9. Since the products in
the irradiations of 1-CN and CHD at -78 °C and room
temperature are different and the analysis of orbital
interaction predicts the more favorable formation of 12
and 1 than 9 and 8, we suspected that secondary
processes occurred in the room-temperature irradiation.
Compounds 1 and 2 can be also formed from the Cope
rearrangement of 12. To explore the existence of 12, a
further irradiation to the photoreaction mixture in the
presence of xanthone at -50 to -40 °C was conducted
for an additional 4 h (Scheme 2).6 Similar separatory
methods resolved a new product (13) in 35% yield, as well
as 1 and 2 in 18% and 39% yields. Seven proton peaks
1
at the region of δ 2.9-4.1 in the H NMR spectrum and
1
3
1
0 peaks at the region of δ 16-46 in the C NMR
F igu r e 3. Low-temperature NMR study for the photoreaction
1
spectrum are consistent with the structure of the cage
adduct (13).
of 1-CN and CHD. (a) H NMR spectrum at -50 °C for the
1
irradiated solution of 1-CN and CHD at -70 to -60 °C. (b) H
NMR spectrum at 25 °C for the resulting solution after
standing at room temperature.
Although the formation of 13 supports the existence
of 12 at the irradiation conditions and 12 is thought to
undergo the facile Cope rearrangement to the [2 + 2]
adducts at room temperature, the distribution of the
products seems to indicate another route for their forma-
tion. In other words, if the adducts 1 and 2 were
exclusively formed from the Cope rearrangement of 12,
the distribution of 1 and 2 (18% and 39%) after the
sensitized reaction should be similar to those (13% and
5
8%) in the direct irradiation. Compounds 1 and 2 may
also be photodissociated at different rates under the
irradiation conditions, and this can be established from
the accounts of the electronic absorption spectra of 1 and
2
. Adduct 1 has an absorption maximum at 271 nm and
a tail up to 310 nm. Adduct 2 has an absorption
maximum at 292 nm and a long tail that reaches beyond
3
70 nm. Considering the irradiation conditions with the
electronic absorptions of 1 and 2, the rate of photodisso-
ciation for 2 would be faster than that for 1, making the
yield of 1 higher.
F igu r e 4. 1H NMR spectrum at -50 °C for the irradiated
solution of 2-CN and CHD at -70 to -60 °C.
This was resolved by a low-temperature NMR study
for the photoreaction mixture of 1-CN and CHD. The
1
H NMR spectrum in CDCl , taken at -50 °C im-
3
Sch em e 3. Cop e Rea r r a n gem en t of Exo-[4 + 4]
mediately after irradiation at -70 to -60 °C for 30 min,
revealed that a novel product (12) was distinguishable
Ad d u ct of 2-CN a n d CHD
1
with a certain amount of 1 (Figure 3a). Another H NMR
spectrum was taken at -50 °C after the reaction mixture
was left at room temperature for 7 min (Figure 3b).
Comparison of the two spectra indicates the total conver-
sion of 12 into 2. In this NMR study, the ratio of 1 and
1
2 was estimated to be about 56:44 at 60% conversion,
which indicated that 1 was the major product. In another
run of 23% conversion, the ratio was 61:39. Upon
irradiation, 1 was formed, but was decomposed to the
starting compounds under the irradiation conditions
A low-temperature NMR study of the irradiated solu-
tion of 2-CN and CHD in CDCl also showed the existence
3
of 3 as well as 4 (Figure 4). The ratio of 3 and 4 was
estimated to be 1:4 at 30% conversion. The results
indicated that 3 was a primary product. The results of
heating a solution of 4 also suggested 3 to be a primary
product. Upon heating 4 at 100 °C for 30 min, both syn-
[2 + 2] adducts (3 and 14) were produced in 37% and
50% isolated yields (Scheme 3). If the Cope rearrange-
ment is a secondary process in the photoreaction of 2-CN
and CHD, the formation of 14 should have been observed
along with 3. The greater difficulty of the Cope rear-
rangement of 4 than that of 12 may be explained by the
(direct and/or sensitized), whereas 2 was formed when
it was left at room temperature through the facile Cope
rearrangement of 12. Among the two possible modes of
the rearrangement, only the conversion of 12 to 2 was
observed. The same mode of the rearrangement was
previously observed with the exo-[4 + 4] cyclodimer of
5
1
-CN and furan, which may be explained by the stabiliz-
ing effect of the cyano group on the C-1 bond breaking
for the rearrangement.

Photocycloaddition of Cyanonaphthalenes
J . Org. Chem., Vol. 63, No. 4, 1998 1215
effect of the cyano group, which had also been observed
(75 MHz) NMR spectra were recorded in CDCl
internal standard unless otherwise noted. IR spectra were
recorded in CHCl All the preparative irradiations were
3
with TMS as
in the thermolysis of cyclodimers of anthracenes and
benzene,8 and the isomerization of quadricyclane to
3
.
norbornadiene.9
performed with a 450-W Hanovia medium-pressure mercury
lamp irradiating through a Pyrex filter. Triple-walled quartz
immersion well with the outer two walls permanently sealed
together and dry ice/solvent baths were used in low-temper-
ature irradiations. The reaction solutions were purged with
nitrogen for more than 20 min before irradiation and during
irradiation. The reactions were followed with either TLC or
In both photocycloaddition reactions, the primary [4
+
4] adducts (12 and 4) are in the exo form. This can be
explained by the secondary orbital interaction of the
LUMO’s of cyanonaphthalenes and the LUMO of CHD
(Figure 2). The exo approach of CHD to cyanonaphtha-
1
H NMR spectrum analysis.
lenes makes the secondary orbital interaction more
favorable, while the endo approach makes the interaction
less favorable. Previous observation of 8, 9, and 11 is
probably due to the decomposition of the primary prod-
ucts and the accumulation of photostable minor products.
It is interesting to note that [2 + 2] and [4 + 4]
photocycloadditions occurred in the irradiations of cy-
anonaphthalenes and CHD, while [4 + 4] and [4 + 2]
Low -Tem p er a tu r e Ir r a d ia tion of 1-CN w ith CHD. A
-
2
solution of 1-CN (1.54 g, 1.00 × 10 mol) and CHD (3.75 g,
-
2
4
.68 × 10 mol) in dichloromethane (150 mL) was irradiated
at -78 °C for 4 h to produce a complex mixture, which was
separated by consecutive silica gel chromatographies eluting
with n-hexane/dichoromethane. In addition to the unreacted
1-CN (19.1 mg), 290 mg (13% based on the consumed 1-CN)
of 1 and 1.35 g of 2 (58% based on the consumed 1-CN) were
1
isolated. 1: mp 103-105 °C (dichloromethane/n-hexane); H
photocycloadditions were observed in the case of naph-
thalene and CHD.10 For both [2 + 2] adducts, the
NMR (200 MHz) δ 7.24 (3H, m, aromatic), 7.01 (1H, m,
aromatic), 6.32 (1H, dd, J ) 10.0, 1.7 Hz, Ar-CHdC), 5.90
cyclohexadiene ring was fused to the 1,2 position of
cyanonaphthalenes, which is consistent with the larger
coefficients at C-1 and C-2 of the LUMO’s than those at
C-3 and C-4 (Figure 2). Since the coefficients at C-1 and
C-4 for the LUMO’s of 1-CN and 2-CN are relatively
smaller compared to those of naphthalene, less favorable
orbital interaction in the [4 + 4] photocycloaddition of
cyanonaphthalenes to CHD is expected. However, the
(
5
1H, m, C-CHdC), 5.69 (1H, dd, J ) 10.0, 4.4 Hz, Ar-CdCH),
.60 (1H, m, CdCH-C-C ), 3.91 (1H, m, CdC-CH-C-CN),
2
3.62 (1H, m, CH-C-C-CN), 3.27 (1H, m, CH-C-CN), 1.84-
1.26 (4H, m, methylene); 13C NMR δ 132.32, 130.18, 128.68,
128.32, 127.74, 127.70, 127.41, 127.19, 125.97, 125.19, 124.44,
4
1
6.88, 43.79, 38.22, 37.69, 22.03, 21.31; IR 3050, 2920, 2205,
440 cm ; UV (cyclohexane) λnm (ꢀ) 271.4 (10300); MS (CI )
-
1
+
m/z 234 (M + 1), 207, 165, 154 (100), 141, 80; HRMS calcd for
C
7
+
1
17
H
16N (MH ) m/z 234.1283, found 234.1283. 2: H NMR δ
[4 + 4] adduct was the major product in the case of 2-CN,
.18 (4H, m), 6.64 (1H, d, J ) 4.3 Hz), 5.95 (1H, m), 5.63 (1H,
while the [2 + 2] adduct was the major product in the
case of 1-CN. Radical ion formation does not seem to
occur because the ∆G’s for electron transfer in the excited
states, disregarding the ion separation energy term, are
m), 3.96 (1H, t, J ) 9.8 Hz), 3.66 (1H, m), 3.48 (1H, m), 2.86
(1H, m), 1.78-1.32 (4H, m); 13C NMR δ 145.65, 132.06, 130.88,
129.47, 128.22, 127.93, 127.15, 125.28, 124.64, 117.42, 113.78,
4
1
2
0.60, 40.56, 39.15, 36.28, 22.69, 21.97; IR 3060, 3025, 2220,
-1
+
495 cm ; UV (acetonitrile) λnm (ꢀ) 291.6 (2930); MS (CI ) m/z
estimated to be -0.42 (1-CN, CHD), -0.20 (2-CN, CHD),
34 (M + 1), 182, 168, 154 (100), 80; HRMS calcd for C17
16
H N
and -0.33 (naphthalene, CHD) eV.1
1-14
Failure to result
+
(MH ) m/z 234.1283, found 234.1284.
in radical ion formation was also reported in the photo-
dimerization of 1-CN and norbornadiene in acetonitrile.15
Therefore, the different distribution of the [2 + 2] and [4
Low -Tem p er a tu r e Ir r a d ia tion of 2-CN w ith CHD. A
-2
solution of 2-CN (1.77 g, 1.16 × 10 mol) and CHD (4.56 g,
-
2
5.69 × 10 mol) in dichloromethane (150 mL) was irradiated
at -78 °C for 5 h. During the irradiation, all of 2-CN had
been consumed and the reaction mixture consisted of 3, 4, and
+
4] adducts may be due to increasing polar character of
4
,15
exciplex intermediacy
and/or steric repulsion of the
5
in the ratio of 21:68:11 by the 1H NMR analysis. Chro-
cyano group in the exo-[4 + 4] approach of CHD to
cyanonaphthalenes.
matographies in several solvent conditions did not resolve the
mixture completely, and some of the products were purified
by chromatographies and recrystallization for the purpose of
full characterization. The isolated yield of 3 was 16% (440.3
mg) on the basis of consumed 2-CN. 3: mp 122-123 °C
1
(
7
)
dichloromethane/n-hexane); H NMR δ 7.19 (2H, m, aromatic),
.03 (1H, m, aromatic), 6.95 (1H, m, aromatic), 6.50 (1H, d, J
9.8 Hz, Ar-CHdC), 6.04 (1H, m, C-CHdC), 5.68 (1H, m,
CdCH-C ), 5.62 (1H, d, J ) 9.8 Hz, Ar-CdCH), 4.26 (1H, d,
J ) 9.4 Hz, Ar-CH-C ), 3.69 (1H, m, CH-C-CN), 2.85 (1H,
2
2
m, Ar-C-CH), 1.84 (2H, m, methylene), 1.50 (1H, m, meth-
ylene), 1.32 (1H, m, methylene); 13C NMR δ 132.49, 131.42,
130.90, 129.84, 128.91, 127.69, 127.59, 127.57, 122.24, 122.12,
45.41, 41.97, 38.04, 37.23, 21.93, 21.74; IR 3015, 2840, 2215,
Exp er im en ta l Section
Ma ter ia ls a n d Gen er a l P r oced u r es. Most reagents and
1
6
solvents were purified by the procedures in the literature.
1
13
-1
Melting points are uncorrected. H (300 MHz) NMR and
C
1640, 1490 cm ; UV (cyclohexane) λnm (ꢀ) 270.2 (7160); MS
+
(
CI ) m/z 234 (M + 1), 207, 182, 154 (100), 81. Anal. Calcd
for C17H15N: C, 87.52; H, 6.48; N, 6.00. Found: C, 87.31; H,
(
8) (a) Yang, N. C.; Yang, X. J . Am. Chem. Soc. 1987, 109, 3804.
b) Yang, X. Ph.D. Thesis, The University of Chicago, 1988. (c) Kimura,
M.; Okamoto, H.; Kashino, S. Bull. Chem. Soc. J pn. 1994, 67, 2203.
9) (a) Kabakoff, D. S.; B u¨ nzli, J .-C. G.; Oth, J . F. M.; Hammond,
W. B.; Berson, J . A. J . Am. Chem. Soc. 1975, 97, 1510. (b) Bellus, D.;
Rist, G. Helv. Chim. Acta 1974, 57, 194.
(
6.50; N, 5.66. 4: mp 95.5-96 °C (dichloromethane/n-hexane);
1
H NMR δ 7.23 (1H, m, CHdC-CN), 7.10 (4H, m, aromatic),
(
6
.17 (1H, m, olefinic), 6.06 (1H, m, olefinic), 3.83 (2H, m, Ar-
(
10) (a) Yang, N. C.; Libman, J . J . Am. Chem. Soc. 1972, 94, 9228.
(13) Ered(1-CN) ) -1.98 V, Ered(2-CN) ) -2.13 V, and Ered(naph-
(
(
b) Kimura, M.; Sagara, S.; Morosawa, S. J . Org. Chem. 1982, 47, 4344.
c) Kimura, M.; Nukada, K.; Satake, K.; Morosawa, S. J . Chem. Soc.,
3
thalene) ) -2.29 V in CH CN (vs SCE). Mattes, S. L., Farid, S. In
Organic Photochemistry; Padwa, A., Ed.; Marcel Dekker: Inc.: New
York, 1983; Vol. 6, Chapter 4. Gilbert, A., Baggot, J . Essentials of
Molecular Photochemistry; CRC Press: Boca Raton, 1991.
Perkin Trans. 1 1986, 885.
11) The free energy changes for electron transfer in the excited state
were estimated while disregarding the ion separation energy term:
ET ) Eox(diene) - Ered(aromatic) - Eexc(aromatic).
CN (vs SCE). Lewis, F. D. In
(
(14) Eexc(1-CN) ) 3.75 eV, Eexc(2-CN) ) 3.68 eV, and Eexc(naphtha-
1
3
∆
G
(
3
lene) ) 3.97 eV in CH CN.
12) Eox(CHD) ) 1.35 V in CH
3
(15) Weng, H.; Roth, H. D. Tetrahedron Lett. 1996, 37, 4895.
(16) Perrin, D. D., Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: Oxford, 1988.
Photoinduced electron transfer; Fox, M. A., Chanon, M., Eds.; Elsevi-
er: Amsterdam, 1988; Part C.

1
216 J . Org. Chem., Vol. 63, No. 4, 1998
Noh et al.
CH), 3.09 (2H, m, Ar-C-CH), 1.35 (4H, m, methylene); 13C
NMR δ 152.47, 142.26, 141.87, 134.83, 134.48, 127.96, 127.87,
mixture of 1-CN (1.53 g, 9.99 × 10 mol) and CHD (3.87 g,
-3
-
2
4.83 × 10 mol) was added xanthone (313 mg), and the
resulting solution was irradiated at -50 to -40 °C for 4 h.
The reaction mixture was separated by a silica gel chroma-
tography, eluting with n-hexane/dichloromethane. Compound
13 was isolated in 35% yield (565 mg) on the basis of consumed
1
2
λ
1
25.88, 125.64, 120.18, 119.41, 50.22, 47.43, 41.73, 41.39,
-
1
4.79, 24.56; IR 3020, 2875, 2205, 1485 cm ; UV (cyclohexane)
+
nm (ꢀ) 276.8 (430), 254.8 (860); MS (CI ) m/z 234 (M + 1), 207,
82, 154 (100), 81. Anal. Calcd for C17H15N: C, 87.52; H, 6.48;
N, 6.00. Found: C, 87.58; H, 6.52; N, 5.64. 5: mp 177-178
1-CN. 13: mp 71-72 °C;
dd, J ) 11.9, 8.3 Hz), 3.76 (1H, t, J ) 8.4 Hz), 3.41 (1H, dd, J
14.5, 7.0 Hz), 3.34 (1H, m), 3.23-3.09 (2H, m), 2.99 (1H,
1
H NMR δ 7.63 (4H, m), 4.03 (1H,
1
°
C (dichloromethane/n-hexane); H NMR δ 7.22 (2H, m,
aromatic), 7.10 (2H, m, aromatic), 6.63 (1H, t, J ) 8.4 Hz,
)
olefinic), 6.36 (1H, t, J ) 8.5 Hz, olefinic), 6.10 (1H, m, olefinic),
13
dd, J ) 14.6, 7.7 Hz), 1.46-1.06 (4H, m); C NMR δ 137.21,
32.11, 129.78, 127.94, 127.38, 127.10, 125.08, 45.94, 41.34,
0.07, 39.25, 37.64, 32.75, 31.92, 30.36, 16.66, 16.37; IR 3010,
5
.64 (1H, m, olefinic), 3.46 (1H, d, J ) 10.9 Hz, Ar-CH-C-
1
4
2
CN), 3.19 (1H, dd, J ) 11.2, 2.5 Hz, Ar-CH-C
td, J ) 9.2, 3.0 Hz, bridgehead), 2.96 (1H, m, cyclobutyl), 2.91
1H, td, J ) 9.2, 3.0 Hz, bridgehead), 2.04 (2H, m, cyclobutyl
and methylene), 1.77 (1H, m, cyclobutyl), 1.58 (3H, m, cyclobu-
2
), 3.05 (1H,
-1
890, 2225, 1455, 1224 cm ; UV (acetonitrile) λnm (ꢀ) 338.0
(
+
(
170), 292.6 (370), 274.0 (490); MS (CI ) m/z 234 (M + 1), 182,
+
1
54 (100), 80; HRMS calcd for C17
found 234.1276.
Cop e Rea r r a n gem en t of Exo-[4 + 4] Ad d u ct of 2-CN
H16N (MH ) m/z 234.1283,
1
3
tyl and methylene), 1.28 (4H, m, methylene); C NMR δ
1
1
3
2
41.45, 140.80, 137.91, 135.49, 131.84, 130.28, 126.93, 126.54,
25.76, 124.57, 53.14, 49.12, 46.94, 43.56, 37.88, 36.12, 35.98,
4.73, 26.64, 24.83, 24.64, 21.85; IR 3025, 2940, 2875, 2850,
-
4
a n d CHD. A solution of 195 mg (8.4 × 10 mol) of 4 in 2 mL
of toluene was stirred at 100 °C for 30 min. The reaction
mixture was separated by silica gel Chromatotron, eluting with
cyclohexane to give 5.7 mg of unreacted 4, 17.1 mg of 2-CN,
-
1
225 cm ; UV (cyclohexane) λnm (ꢀ) 275.4 (290), 267.2 (310);
+
MS (CI ) m/z 314 (M + 1, 100), 234, 154, 80; HRMS calcd for
+
C
23
H
24N (MH ) m/z 314.1909, found 314.1915.
Ir r a d ia tion of th e Ir r a d ia ted Mixtu r e of 2-CN a n d
CH D in t h e P r esen ce of Xa n t h on e. After dichlo-
9
°
5 mg (50%) of 3, and 70.3 mg (37%) of 14. 14: mp 120-122
1
C (dichloromethane/n-hexane); H NMR δ 7.23 (1H, m), 7.15
a
-3
(1H, m), 7.00 (3H, m), 6.00 (1H, m), 5.86 (1H, m), 4.05 (1H, t,
romethane (150 mL) solution of 2-CN (1.53 g, 9.98 × 10 mol)
-
2
J ) 9.9 Hz), 3.67 (1H, tt, J ) 9.9, 1.5 Hz), 3.47 (1H, m, J )
and CHD (3.52 g, 4.39 × 10 mol) was irradiated at -78 °C
8
.9, 1.9 Hz), 2.95 (1H, m), 1.79-1.29 (4H, m); 1 C NMR δ
3
for 4 h, xanthone (313 mg) was added. The resulting solution
1
141.59, 133.56, 131.02, 130.71, 130.62, 128.86, 128.20, 127.01,
124.70, 120.09, 111.34, 40.74, 39.88, 39.16, 36.64, 22.54, 21.92;
was irradiated at -50 to -40 °C for 4 h. As estimated by H
NMR, the relative yields of 3, 4, 5, and 6 based on the
consumed 2-CN were 16%, 22%, 23%, and 39%, respectively.
The reaction mixture was separated by a silica gel chroma-
tography eluting with cyclohexane/benzene for the purpose of
analysis. 6: mp 159.5-160.5 °C (dichloromethane/cyclohex-
-
1
IR 3020, 2925, 2200, 1212, 1205 cm ; UV (cyclohexane) λnm
+
(ꢀ) 299.8 (960), 289.8 (920); MS (CI ) m/z 234 (M + 1), 182,
+
154 (100), 80; HRMS calcd for C17
found 234.1276.
H
16N (MH ) m/z 234.1283,
1
ane); H NMR δ 7.25 (2H, m), 7.15 (2H, m), 4.18 (1H, d, J )
1
1.8 Hz), 4.08 (1H, dd, J ) 11.8, 8.3 Hz), 3.47 (2H, m), 3.33
Ack n ow led gm en t. This research was financially
supported by Lotte Fellowship of Lotte Scholarship
Foundation and Korean Ministry of Education through
Research Fund (BSRI-96-3448).
(
2H, m), 3.11 (1H, dd, J ) 14.9, 8.1 Hz), 1.29 (2H, m), 1.13
13
(2H, m); C NMR δ 137.48, 135.39, 129.46, 129.44, 127.44,
1
3
26.95, 122.60, 44.33, 41.05, 37.80, 37.48, 37.33, 36.05, 30.64,
0.60, 16.35, 16.25; IR 3010, 2890, 2220, 1455 cm-1; UV
+
(
cyclohexane) λnm (ꢀ) 273.8 (190), 265.0 (260); MS (CI ) m/z
+
2
34 (M + 1), 207, 154, 80 (100); HRMS calcd for C17
m/z 234.1283, found 234.1283.
P r ep a r a tion of Ca ge Ad d u ct of 2-CN a n d CHD.
dichloromethane solution (5 mL) of 4 (100 mg) and xanthone
30 mg) was irradiated for 2 h and separated by silica gel
H
16N (MH )
Su p p or tin g In for m a tion Ava ila ble: 1H NMR spectra of
, 2, 3, 4, and 5, NOESY spectrum of 1, COSY spectrum of 3,
and COSY and NOESY spectra of 5 (9 pages). This material
is contained in libraries on microfiche, immediately follows this
article in the microfilm version of the journal, and can be
ordered from the ACS; see any current masthead page for
ordering information.
1
A
(
Chromatotron, eluting with cyclohexane/benzene to afford 78.7
mg of 6 (79%) and 15 mg of 2-CN.
Ir r a d ia tion of th e Ir r a d ia ted Mixtu r e of 1-CN a n d
CHD in th e P r esen ce of Xa n th on e. To the photoreaction
J O971748B