Reaction of vinylcarbenoids with benzaldehydes: Formation of vinylcarbonyl ylides followed by ring closure to oxiranes and dihydrofurans

Article abstract of DOI:10.1021/jo015618l

Rh₂(OAc)₄-catalyzed reaction of vinyldiazo compound 1a in the presence of p-methoxybenz- 2a, mesit- 2b, and p-chlorobenzaldehyde 2c gave a mixture of isomeric vinyloxiranes 3a-c and 4a-c, and sterically unstable (E)-dihydrofurans 5a-c, but not stable (Z)-dihydrofurans 6. However, the reactions with p-nitro-2d and 2,4-dinitrobenzaldehyde 2e gave (Z)-dihydrofurans 6d,e along with 3d, 4d, and 5d,e. The reaction in the presence of maleic anhydride and dimethyl fumarate gave single 1,3-dipolar cycloadducts 11 and 13, respectively, indicating that a single conformer, the sterically unstable endo-aryl-endo-cyanostyryl carbonyl ylide 14 (15), is initially formed in the reaction of 1 with 2. It was concluded that the endo-vinyl-exo-aryl vinylcarbonyl ylides 17a-c arising from 2a-c undergo disrotatory cylization to exlusively produce 5, whereas the ylides 17d,e arising from 2d,e undergo partly symmetry-forbidden conrotaory cyclization to sterically stable transdiaryldihydrofurans 6d,e as well as the symmetry-allowed process to 5d,e.

Full text of DOI:10.1021/jo015618l

J . Org. Chem. 2001, 66, 5395-5404
5395
Rea ction of Vin ylca r ben oid s w ith Ben za ld eh yd es: F or m a tion of
Vin ylca r bon yl Ylid es F ollow ed by Rin g Closu r e to Oxir a n es a n d
Dih yd r ofu r a n s
Masashi Hamaguchi,* Hiroshi Matsubara, and Toshikazu Nagai
Department of Materials Chemistry, Graduate School of Engineering, Osaka University,
Toyonaka 560-0043, J apan
hamaro@ch.wani.osaka-u.ac.jp
Received March 6, 2001
Rh2(OAc)4-catalyzed reaction of vinyldiazo compound 1a in the presence of p-methoxybenz- 2a ,
mesit- 2b, and p-chlorobenzaldehyde 2c gave a mixture of isomeric vinyloxiranes 3a -c and 4a -c,
and sterically unstable (E)-dihydrofurans 5a -c, but not stable (Z)-dihydrofurans 6. However, the
reactions with p-nitro- 2d and 2,4-dinitrobenzaldehyde 2e gave (Z)-dihydrofurans 6d ,e along with
3d , 4d , and 5d ,e. The reaction in the presence of maleic anhydride and dimethyl fumarate gave
single 1,3-dipolar cycloadducts 11 and 13, respectively, indicating that a single conformer, the
sterically unstable endo-aryl-endo-cyanostyryl carbonyl ylide 14 (15), is initially formed in the
reaction of 1 with 2. It was concluded that the endo-vinyl-exo-aryl vinylcarbonyl ylides 17a -c arising
from 2a -c undergo disrotatory cylization to exlusively produce 5, whereas the ylides 17d ,e arising
from 2d ,e undergo partly symmetry-forbidden conrotaory cyclization to sterically stable trans-
diaryldihydrofurans 6d ,e as well as the symmetry-allowed process to 5d ,e.
In tr od u ction
carbene/carbenoid onto the oxygen atom of a carbonyl
group4-7 have been known as traditional methods of
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10.1021/jo015618l CCC: $20.00 © 2001 American Chemical Society
Published on Web 07/11/2001

5396 J . Org. Chem., Vol. 66, No. 16, 2001
Hamaguchi et al.
generation of carbonyl ylides. Recently, intermolecular4
or intramolecular reaction5-7 of carbenes and metallo-
carbenoids with carbonyl compounds have been widely
studied, and intermolecular or intramolecular 1,3-dipolar
cycloaddition of the resultant carbonyl ylides have been
utilized as a synthetic method of a oxygenated five-
membered heterocycle or a complex polycyclic oxygen
heterocycle.4-7 Despite enormous studies of carbonyl
ylides, some studies on vinylcarbonyl ylides via thermal
ring opening of vinyloxiranes have been reported.8-13 The
thermal ring opening of oxiranes to carbonyl ylides
requires high temperature, whereas the generation of
carbonyl ylides via the carbenoid-carbonyl reaction can
be performed under very mild conditions. A few examples
of the generation of vinylcarbonyl ylides, which cyclized
to dihydrofurans, from the reaction of carbenes with R,â-
unsaturated ketones have been reported.14 Vinylcarbonyl
ylides can undergo electrocyclic ring closures to oxiranes
as a 4π electronic component and also to dihydrofurans
as a 6π electronic component.
Sch em e 1
Sch em e 2
Here we report the first example of the generation and
reactions of vinylcarbonyl ylides from the reaction of the
vinyl carbenoids with some substituted benzaldehydes.15
Resu lts
R h 2(OAc)4-Ca t a lyzed Decom p osit ion of 2-(p -
Ch lor op h e n yl)-4-d ia zo-4-p h e n yl-cis-2-b u t e n e n i-
tr ile (1a ) in th e P r esen ce of Su bstitu ted Ben za ld e-
h yd es. A benzene solution of 1a (1 mmol) was added
dropwise over 1 h to a substituted benzaldehyde 2 (5
mmol) and a catalytic amount of Rh2(OAc)4 in benzene
at 50 °C under an argon atmosphere. The reaction
(8) (a) Chou, W.-N.; White, J . B. Tetrahedron Lett. 1991, 32, 7637.
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chardt, B. Chem. Ber. 1978, 111, 3665. (g) Eberbach, W.; Burchardt,
B. Tetrahedron Lett. 1976, 3887. (h) Eberbach, W.; Carre, J . C. Chem.
Ber. 1981, 114, 1027. (i) Eberbach, W.; Seiler, W.; Fritz, F. Chem. Ber.
1980, 113, 875. (j) Eberbach, W.; Burchardt, B.; Trostmann, U.
Tetrahedron Lett. 1979, 4049. (k) Eberbach, W.; ko¨nig, G.; Trostmann,
U. Tetrahedron Lett. 1979, 4649. (l) Roser, J .; Eberbach, W. Tetrahe-
dron Lett. 1984, 25, 2455. (j) Eberbach, W.; Roser, J . Heterocycles 1985,
23, 2797.
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1980, 45, 428. (b) Bourelle-Wagnier, F.; Vincent, M.; Chuche, J .
Tetrahedron Lett. 1978, 283. (c) Medimagh, M. S.; Chuche, J . Tetra-
hedron Lett. 1977, 793. (d) Pommelet, J . C.; Manisse, N.; Chuche, J .
Tetrahedron 1972, 28, 3929. (e) Paladini, J . C.; Chuche, J . Tetrahedron
Lett. 1971, 4383.
Ta ble 1. P r od u ct Ra tios of th e Rea ction s of th e
Vin yld ia zo Com p ou n d 1a w ith Va r iou s Su bstitu ted
Ben za ld eh yd es a t 50 °Ca
ratio (%)
substituted
run
benzaldehyde
Ar
3
4
5
6
1
2
3
4
5
6
7
2a
2b
2c
2d
2e
2f
p-CH3O-C6H4
2,4,6-(CH3)3-C6H2
p-Cl-C6H4
37 29 34
29 64
22 58 20
13 21 61
0
7
0
0
5
p-NO2-C6H4
2,4-(NO2)2-C6H4
2,6-(NO2)2-C6H4
2,4,6-(NO2)3-C6H2
0
0
0
0
0
0
38 62
0
0
0
0
2g
The ratios were determined by the 1H NMR spectra of the
reaction mixtures.
a
(10) (a) Crawford, R. J .; Lutener, S. B.; Cockcroft, R. D. Can. J .
Chem. 1976, 54, 3364. (b) Crawford, R. J .; Vukov, V.; Tokunaga, H.
Can. J . Chem. 1973, 51, 3718.
mixtures were separated by column chromatography to
give (Z)- and (E)-vinyloxiranes (3 and 4) and dihydro-
furans (5 and 6) (Scheme 2 and Table 1). The reaction
with p-methoxybenz- 2a , mesit- 2b, and p-chlorobenz-
aldehyde 2c furnished sterically unstable cis-diaryldi-
hydrofurans 5a -c, but not stable trans-diaryldihydro-
furans 6a -c, along with the oxiranes 3a -c and 4a -c
in ratios shown in Table 1 (runs 1-3). A small amount
of trans-diaryldihydrofurans 6d were also obtained along
with other products in the reaction of p-nitrobenzalde-
hyde 2d (run 4). However, the reaction with 2e did not
afford any oxiranes but cis-diaryldihydrofuran 5e and
trans-diaryldihydrofuran 6e in a ratio of 2:3 (run 5). 2,6-
Dinitro- 2f and 2,4,6-trinitrobenzaldehyde 2g bearing two
nitro groups at ortho-positions did not react with the
carbenoid (runs 6 and 7).
(11) (a) Hudlicky, T.; Barbieri, G. J . Org. Chem. 1991, 56, 4598. (b)
Hudlicky, T.; Fleming, A.; Lovelace, T. C. Tetrahedron 1989, 45, 3021.
(c) Hudlicky, T.; Lovelace, T. C. Synth. Commun. 1990, 20, 1721. (d)
Hudlickly, T.; Reed, J . W. Rearrangements of vinylcyclopropanes and
related systems. In Comprehensive Organic Chemistry; Pergamon
Press: New York, 1991; Vol. 5, Chapter 8. (e) Hudlicky, T.; Fan, R.;
Reed, J . W.; Gadamsetti, K. G. Org. React. 1992, 41, Chapter 1.
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Acta 1985, 68, 1089.
(13) Paulson, D. R.; Tang, F. Y. N.; Sloan, R. B. J . Org. Chem. 1973,
38, 3967.
(14) (a) Anac, O.; Daut, A. Liebigs Ann./ Recl. 1997, 1249. (b)
Murayama, S. T.; Spencer, T. A. Tetrahedron Lett. 1969, 4479. (c)
Spencer, T. A.; Villarica, D. L.; Storm, D. L.; Weaver, T. D.; Friary, R.
J .; Posler, J .; Shafer, P. R. J . Am. Chem. Soc. 1967, 89, 5497. (d) Storm,
D. L.; Spencer, T. A. Tetrahedron Lett. 1967, 1865. (e) Hodge, P.;
Edwards, J . A.; Fried, J . H. Tetrahedron Lett. 1966, 5175.
(15) A preliminary report on some of the results was published;
see: Hamaguchi, M.; Matsubara, H.; Nagai, T. Tetrahedron Lett. 2000,
41, 1457.

Reaction of Vinylcarbenoids with Benzaldehydes
J . Org. Chem., Vol. 66, No. 16, 2001 5397
Ta ble 2. P r od u ct Ra tios of th e Rea ction s of th e
Vin yld ia zo Com p ou n d 1b w ith Su bstitu ted
Ben za ld eh yd es a t 50 °Ca
Sch em e 3
ratio (%)
substituted
run
benzaldehyde
Ar
7
8
9
10
1
2
3
2a
2c
2d
p-CH3O-C6H4
p-Cl-C6H4
p-NO2-C6H4
50
16
1
50
82
98
0
2
1
0
0
0
a
The ratios were determined by the 1H NMR spectra of the
reaction mixtures.
Ta ble 3. P r od u cts Ra tios in th e Rea ction s of th e
Vin yld ia zo Com p ou n d 1a ,b in th e P r esen ce of 5 Mola r
Equ iv of Su bstitu ted Ben za ld eh yd es a n d Ma leic
An h yd r id e in Ben zen e a t 50 °Ca
ratio (%)
It is worth noting that electron-donating substituents
of benzaldehydes increased the relative yields of (Z)-
vinyloxiranes 3, whereas electron-withdrawing substit-
uents increased the sum of the yields of 4 and dihydro-
furans and more electronegative groups favored formation
of dihydrofurans.
subst benz-
aldehydes
11 or
3(7) 4(8) 5(9) 6(10) 12
run
1
Ar
1
2
3
4
5
6
1a
1a
1a
1a
1b
1b
2a
2c
2d
2e
2a
2d
p-CH3O-C6H4
p-Cl-C6H4
p-NO2-C6H4
2,4-(NO2)2-C6H3
p-Cl-C6H4
0
8
11
0
0
0
2
8
18
0
12
23
22
8
0
0
4
76
76
16
0
88
77
51
39
0
61
0
IR spectra of all products showed the absence of
carbonyl groups. The structures of these products were
determined on the basis of 1H and 13C NMR. For example,
the oxirane carbons in 3c and 4c were observed at δ 65.6
(d), 66.6 (s) and at δ 67.6 (d), 65.3 (s), respectively, and
the dihydrofuran carbons of 5c were observed at δ 160.1
(s), 97.7 (d), 90.8 (d), and 55.7 (s). The proton signals of
phenyl and aryl groups on the oxirane ring of 3 appeared
at ca. 0.2 ppm higher fields compared to those of 4,
indicating vicinal cis-aryl groups in 3 and trans-aryl
groups in 4. Further supports for their structures were
obtained from the NOE difference analysis of 3 and 4.
The proton signals of 4-phenyl and 5-aryl groups of
dihydrofurans 5a -e appeared at higher fields, indicating
vicinal cis-aryl groups. Restriction of rotation of the
mesityl substituent was observed in the product 5b with
mesitaldehyde. Two ortho-methyl protons of 5b appeared
nonequivalent at δ 2.70 and 1.80 as broad singlets.
Elevation of the temperature to 50 °C caused the two
broad singlets to collapse to a sharp singlet. Structures
of 6d and 6e were determined by the NOE difference
analysis and appearance of 2-H protons of 6d and 6e at
ca. 0.7 ppm higher fields than the corresponding protons
of 5d and 5e.
p-NO2-C6H4
0
0
The ratios were determined by the 1H NMR spectra of the
a
reaction mixtures.
Sch em e 4
way as described above. The methyl singlet of 7 appeared
at ca. 0.45 ppm higher field than that of 8 due to the
shielding effect of the phenyl group cis to it.
Rea ction of 1 w ith Su bstitu ted Ben za ld eh yd es in
th e P r esen ce of Dip ola r op h iles. We attempted to trap
the carbonyl ylide intermediates using reactive dipolaro-
philes. The Rh2(OAc)4-catalyzed decompositions of the
vinyldiazo compounds 1a ,b in the presence of 5 molar
equiv of substituted benzaldehydes and dipolarophiles at
various temperatures were carried out and gave 1,3-
dipolar cycloadducts along with small amounts of 3, 4,
and 5 (and also with 6d in the case of 2d ).
The Rh2(OAc)4-catalyzed reaction of 1a with p-chloro-
benzaldehyde in the presence of maleic anhydride at 50
°C produced the single cycloadduct 11c (isolated yield
71%) along with small amounts of 3c, 4c, and 5c (Table
3). Careful inspection of the NMR spectrum of the
reaction mixture showed the absence of any other iso-
meric cycloadducts. The structure of 11c, in which the
p-chlorophenyl and the cyanostyryl group are syn to the
cyclic anhydride ring, was determined on the basis of
large coupling constants (J ) 8.3 Hz) among three
protons (3-H, 4-H, and 5-H) on the tetrahydrofuran ring
and NOE difference studies as shown in Scheme 4. On
irradiation of the proton (3-H) at δ 4.53 (d), distinctive
enhancement of the signals of the ortho protons (31%) of
2-phenyl group and 4-H on tetrahydrofuran ring (10%)
at δ 3.81 (t) was observed. The irradiation of the signal
at δ 3.81 (t) caused distinctive enhancement of the
doublets at δ 4.53 (10%) and 5.28 (14%).
Rea ction of 2-(p-Ch lor op h en yl)-4-d ia zo-cis-2-p en -
ten en itr ile (1b) w ith Su bstitu ted Ben za ld eh yd es.
Reactions of 1b with substituted benzaldehydes 2 (Scheme
3) under the same condition as described above gave a
mixture of (E)-vinyloxiranes 7, (Z)-vinyloxiranes 8, and
very small amounts of cis-diaryldihydrofurans 9 in ratios
shown in Table 2. Electron-withdrawing substituents of
benzaldehydes increased the relative yields of (Z)-vinyl-
oxiranes 8. The reaction with p-nitrobenzaldehyde 2d
predominantly gave 8d . Structures of these products
were determined on the basis of NMR spectra in a similar

5398 J . Org. Chem., Vol. 66, No. 16, 2001
Hamaguchi et al.
Sch em e 5
The Rh2(OAc)4-catalyzed reaction of 1b with 2c in the
presence of maleic anhydride also gave the single cyclo-
adduct 12c (isolated yield 68%) along with small amounts
of 7c, 8c, and 9c. The NMR spectrum of 12c was very
similar to that of 11c; large coupling constants (J ) 8.3
Hz) among three THF ring protons and the irradiation
of the methyl protons of 12c caused distinctive enhance-
ment of the signals of 3-H, 5-H, and the vinylic proton.
The Rh2(OAc)4-catalyzed decomposition of 1a in the
presence of 5 molar equiv of p-chlorobenzaldehyde and
dimethyl fumarate gave sole cycloadduct 13c along with
3c, 4c, and 5c. The structure of 13c was determined on
the basis of the NOE difference analysis. Irradiation of
the tetrahydrofuran ring proton at δ 4.31 (d) and the
doublet of doublets at δ 3.80 caused distinctive enhance-
ment of the signals of the ortho protons of the 5-phenyl
group and ortho protons of the 2-p-chlorophenyl group,
respectively, while irradiation of the proton at δ 5.07 (d)
caused distinctive enhancement of the proton at δ 4.31
(dd) and the ortho protons of the 2-p-chlorophenyl and
5-phenyl groups. These results are consistent with the
structural assignment shown.
Ta ble 4. P r od u cts Ra tios in th e Rea ction s of Vin yld ia zo
Com p ou n d 1a w ith p-Ch lor oben za ld eh yd e 2c in th e
P r esen ce of Ma leic An h yd r id e in Dich lor oeth a n e a t
Va r iou s Tem p er a tu r esa
product ratios (%)
temp (°C)
3c
4c
5c
11c
0
40
50
60
80
0
4
8
10
10
0
5
8
10
17
0
6
8
12
17
100
84
76
68
56
a
The ratios were determined by the 1H NMR spectra of the
reaction mixtures.
Sch em e 6
The reactions of 1a with several substituted benzalde-
hydes 2 in the presence of maleic anhydride were carried
out in benzene at 50 °C in order to study substituent
effects of benzaldehydes on the ratios of intermolecular
1,3-dipolar cycloaddition to intramolecular cyclization of
vinylcarbonyl ylides. The product ratios of the cycload-
duct 11 increased with the electron-donating ability of
substituents and decreased with increase in the number
of nitro groups on benzaldehydes, suggesting that an
electron-donating group enhances the rates of 1,3-dipolar
cycloaddition compared to intramolecular cyclization. The
vinylcarbonyl ylide arising from 2e did not produce any
cycloadduct 11e, but 5e and 6e (Table 3, run 4). The
vinylcarbonyl ylide arising from 1b (R ) Me) showed a
tendency to form much more intermolecular products 12
than 1a (R ) Ph) as shown in Table 3, indicating that
the vinyl carbonyl ylide from 1b is more reactive toward
maleic anhydride.
We examined temperature dependency of the product
ratios of cycloadduct 11c. The reactions of 1a with 2c in
the presence of maleic anhydride in dichloroethane were
carried out at various temperatures. The yield of 11c
increased with lowered temperature. The cycloadduct
11c, a bimolecular product, was formed quantitatively
at 0 °C, whereas the relative yield of 11c decreased with
elevation of the reaction temperature as shown in Table
4.
Ta ble 5. Ha lf-Life P er iod s of th e Th er m a l Isom er iza tion
of 3c a n d 4c to 5c in Tetr a ch lor oeth a n e
t1/2 (min)
temp (°C)
3c
4c
108.5
113.2
24.4
15.8
163.0
98.2
(Scheme 6). During thermal isomerization, a mutual
isomerization between 3a ,c and 4a ,c was not observed
by HPLC. The rates for the thermal isomerization of 3c
and 4c in tetrachloroethane at 108.5 and 113.2 °C were
measured using HPLC. The rate for isomerization of 3c
was 6-7 times faster than that for 4c (Table 5). Heating
of 3d and 4d in refluxing toluene gave cis-diaryldihy-
drofuran 5d and trans-diaryldihydrofuran 6d in a ratio
of 9:1, which is very similar to the case of the carbenoid-
2d reaction.
Th er m a l Isom er iza tion of Vin yloxir a n es to Di-
h yd r ofu r a n s. The hitherto known facts of the thermal
conversion of vinyl oxiranes to dihydrofurans via vinyl
carbonyl ylides8-13 prompted us to study the thermal
isomerization of vinyloxiranes 3 and 4. On heating to over
100 °C in tetrachloroethane, vinyloxiranes 3a ,c and 4a ,c
isomerized to (E)-dihydrofurans 5a ,c, quantitatively
We attempted to trap carbonyl ylide intermediates
during the thermal isomerization to the dihydrofuran
using maleic anhydride. However, oxiranes 3 and 4 in
the presence of 5 molar equiv of maleic anhydride in

Reaction of Vinylcarbenoids with Benzaldehydes
J . Org. Chem., Vol. 66, No. 16, 2001 5399
Sch em e 7
Sch em e 8
11 suggests that the initially formed vinyl carbonyl ylide
would be either 14 (15) or 18 (19).
On the other hand, heating 3a ,c and 4a ,c in tetra-
chloroethane over 100 °C resulted in quantitative isomer-
ization to the cis-dihydrofuran 5a ,c. Furthermore, the
rate of isomerization of 3c was 6-7 times faster than that
of 4c. However, on heating the oxiranes in maleic
anhydride, any trapping adducts of intermediate carbonyl
ylide were not observed. Although the carbonyl ylides 14
(15) and 18 (19) could be generated from conrotatory ring
opening of 3, the ring opening to the endo-aryl ylides 14
(15) is extremely difficult because of the steric repulsion
between both of the endo-substituents of 14 (or 15). It
implies that the vinylcarbonyl ylides 18 (19) generated
from thermal ring opening of the vinyloxiranes are
different from the initially formed ones in the carbenic
reaction, which must be very reactive toward maleic
anhydride. The stable exo-aryl ylides 18 (19) from 3
isomerize to 16 (17) via C-O bond rotation followed by
fast disrotatory cyclization to 5 (Scheme 10). During the
thermal isomerization the intermediates vinylcarbonyl
ylides 16 (17) and 18 (19) are less reactive toward maleic
anhydride and convert to the products without capturing
maleic anhydride. It is well-known that sterically stable
endo-vinylcarbonyl ylides such as 17 undergo disrotatory
cyclization to give sterically unstable cis-dihydrofurans
such as 5.8-13
refluxing toluene yielded only dihydrofurans. Even with
heating at 110 °C for 6 h in maleic anhydride, the
dihydrofuran 5 was predominantly formed without for-
mation of any cycloadducts between the carbonyl ylides
and maleic anhydride.
Discu ssion
Mech a n ism of Rea ction of Vin ylca r ben oid s w ith
Ald eh yd es. In general, the reaction of carbenoids with
aldehydes has been known to proceed via carbonyl ylides,
which are known as a 1,3-dipole.16 So the present
reactions also seem to be a multistep reaction involving
vinylcarbonyl ylides as intermediates. Possible conforma-
tions of vinylcarbonyl ylides formed are 14-21, which
are classified into four categories by the difference of
configuration of an aryl and a cyanostyryl group (Scheme
7).
If these cyclizations proceed according to Woodward-
Hoffmann rules,17 the precursors of oxiranes 3 and 4 and
dihydrofurans 5 should be the vinylcarbonyl ylides 18
or 19 (exo-vinyl-exo-aryl), 16 or 17 (endo-vinyl-exo-aryl),
and 17, respectively. Apparently sterically hindered
conformers 14 or 15 (endo-vinyl-endo-aryl) and 20 or 21
(exo-vinyl-endo-aryl), in which both bulky substituents
are located at endo-positions, seem to be unstable ones
and to be difficult to form. Therefore, we attempted to
trap carbonyl ylide intermediates using maleic anhy-
dride, resulting in the formation of the single cycloadduct
11 among all possible diastereomeric cycloadducts. The
cycloadducts 11 would be formed by endo-addition of
maleic anhydride to the ylide 14 (15) or exo-addition to
the ylide 18 (19) (Scheme 8). Predominant formation of
Thus, it is concluded that the vinyl carbenoid reacts
with benzaldehydes to initially form the endo-vinyl-endo-
aryl ylides 14 (15), which undergoes conrotatory ring
closure as a 4π electron system to (Z)-oxirane 3 or
competitive rotation around C-O bond, giving more
stable carbonyl ylides 16 (17). Conrotatory cyclization of
the endo-vinylcarbonyl ylide 16 to oxirane 4 can compete
with disrotatory ring closure to 5 (Scheme 9).8a In the
presence of maleic anhydride, the initially formed endo-
vinyl-endo-aryl ylide 14 (15) is effectively captured by
maleic anhydride to give the 1,3-dipolar cycloadduct 11
before conversion to (Z)-oxirane 3 or isomerization to 16
(17). At elevated temperature the intramolecular con-
rotatory ring closure and rotation around the ArCH-O
bond of 14 (15) can compete with the bimolecular 1,3-
dipolar cycloaddition with maleic anhydride as shown in
Table 4.
Mech a n ism of Th er m a l Isom er iza tion s of Vin yl-
oxir a n es 3 a n d 4 to Dih yd r ofu r a n s 5 a n d 6. Thermal
conrotatory ring opening of (E)-oxiranes 4 leads to stable
endo-vinyl-exo-aryl ylides 16 (17) bearing only one sub-
stituent at an endo position. The endo-vinyl ylide 17
undergoes disrotatory ring closure to (E)-dihydrofuran
5 with vicinal cis-diaryl groups. Conrotatory ring opening
(16) Huisgen, R. Angew. Chem., Int. Ed. Engl. 1963, 2, 565.
(17) Woodward, R. B.; Hoffmann, R. Angew. Chem., Int. Ed. Engl.
1969, 8, 781.

5400 J . Org. Chem., Vol. 66, No. 16, 2001
Hamaguchi et al.
Sch em e 9
Sch em e 10
of (Z)-oxirane 3 gives predominantly exo-vinyl-exo-aryl
ylide 18 (19) bearing one substituent at the endo-position,
which is more stable than endo-vinyl-endo-aryl 14 (15)
bearing two substituents at endo-positions. The ylide 18
(19) undergoes rotation around RC-O bond to give 16
(17) and then cyclization to 5 as shown in Scheme 10.
On the other hand, the sterically stable trans-di-
aryldihydrofurans 6d and 6e were obtained along with
(E)-dihydrofurans 5d ,e only in the reactions of 1a with
p-nitrobenzaldehyde 2d and 2,4-dinitrobenzaldehyde 2e
(runs 4 and 5 in Table 1). Formation of 6 can be
interpreted by two possible pathways. One is symmetry-
allowed disrotatory ring closure of the initially formed
ylide 15, and the alternative one is symmetry-forbidden
conrotatory ring closure of more stable ylide 17. The fact
that 6d and 5d were formed in a similar ratio not only
in the reaction of vinylcarbenoids with 2d but also in the
thermal isomerization of 3d or 4d suggests that 6d and
5d were formed from the same intermediate in both
reactions. However, the generation of the most unstable
carbonyl ylides 14 (15) from ring opening of 3d is not
plausible. So the symmetry-forbidden conrotatory ring
closure process of 17 should be concluded to be the more
likely pathway for formation of 6. Unlike azomethine
ylides, carbonyl ylides, having more “π-diradical charac-
ter”, allow a symmetry-forbidden process to a stable

Reaction of Vinylcarbenoids with Benzaldehydes
J . Org. Chem., Vol. 66, No. 16, 2001 5401
Sch em e 11
conrotatory cyclization to dihydrofurans 5. The initially
formed vinylcarbonyl ylides 14 are efficiently captured
by maleic anhydride to give only a single cycloadduct 11
(12) through the transition state stabilized by secondary
orbital overlap between the vinyl moiety of the ylide’s
HOMO and the carbonyl moiety of the maleic anhydride’s
LUMO. The vinylcarbonyl ylides 16 and 18 arising from
thermal ring opening of 3 or 4 are inert to maleic
anhydride. The ylides 17a -c arising from the reaction
of the carbenoids with 2a -c or pyrolysis of 3a -c and
4a -c undergo disrotatory cyclization to exlusively form
the sterically unfavorable cis-diaryldihydrofurans 5,
whereas the ylides 17d ,e undergo partly a symmetry-
forbidden conrotatory cyclization to the sterically stable
trans-diaryldihydrofurans 6d ,e and a symmetry-allowed
process to 5d ,e.
Sch em e 12
Exp er im en ta l Section
1H NMR (270.05 MHz) and 13C NMR (60.40 MHz) spectra
were recorded on a J EOL EX-270 instrument in a CDCl3
solution using TMS as an internal standard. IR spectra were
recorded on a J ASCO FT-IR-300E. All melting points were
measured with a Yanagimoto melting point apparatus and
were not corrected. Phenyldiazomethane20 and an ethereal
solution of diazoethane21 were prepared by a procedure
described in Organic Synthesis.
isomeric product in some cases due to configuration
interaction.2a,18,19
During thermal isomerization of 3 and 4 to 5, there
was no observation of mutual isomerization between 3
and 4. Crawford et al. studied thermal isomerization in
the gas phase of the parent vinyloxirane and calculated
∆H‡ and ∆S‡ for racemization of vinyloxirane and its
isomerization to dihydrofuran as shown in Scheme 11.10a
Although ∆H‡ for racemization of the vinyloxirane is
smaller than that of isomerization to the dihydrofuran,
∆S‡ for racemization is smaller than that for isomeriza-
tion to the dihydrofuran. This suggests that cyclization
of the vinylcarbonyl ylide to dihydrofuran becomes more
favorable than cyclization to vinyloxirane with increasing
temperature. Under the high-temperature condition ac-
companying ring opening of these vinyloxiranes 3 and
4, the rate for cyclization of the carbonyl ylides 16 (17)
to 5 might be faster than that for cyclization to the
oxiranes 4.
F or m a tion of Sin gle Cycloa d d u cts of Vin ylca r -
bon yl Ylid es w ith Dip ola r op h iles. Predominant for-
mation of endo-addition products of maleic anhydride and
dimethyl fumarate to ylide 14 is explained by stabiliza-
tion of the transition state due to preferred secondary
orbital overlap between the vinyl moiety of ylide’s HOMO
and the carbonyl moiety of the maleic anhydride’s or
dimethyl fumarate’s LUMO as shown in Scheme 11.
Thus, the formation of single cycloadduct 11, 12, or 13
adds strong support for the initial formation of the endo-
vinyl-endo-aryl carbonyl ylide 14 (15) in the reaction with
benzaldehydes.
P r epar ation of tr a n s- an d cis-3-Ch lor o-2-(p-ch lor oph en -
yl)p r op en en itr ile. A mixture of p-chlorobenzyl cyanide (75.7
g, 0.5 mol) and ethyl formate (37.0 g, 0.5 mol) was added
dropwise to a stirred solution of sodium hydride (12.0 g, 0.5
mol) in 300 mL of anhydrous ethylene glycol dimethyl ether
in an ice bath. After addition was completed, the reaction
mixture was gradually warmed to 60 °C and stirred for 2 h.
The precipitated sodium salt of 3-hydroxy-2-(p-chlorophenyl)-
propenenitrile was isolated by filtration, dissolved in water,
and then acidified by addition of 0.5 N HCl solution. The
precipitated 3-hydroxy-2-(p-chlorophenyl)propenenitrile was
filtered and recrystallized from ether. trans- and cis-3-Chloro-
2-(p-chlorophenyl)propenenitrile was prepared from 3-hydroxy-
2-(p-chlorophenyl)propenenitrile according to Cariou’s proce-
dure.22 Phosphorus pentachloride (29.0 g) was carefully added
to 3-hydroxy-2-(p-chlorophenyl)propenenitrile (25.0 g) and
pyridine (11.0 g) in 250 mL of benzene and refluxed for 5 h.
The reaction mixture was poured into 200 g of crushed ice and
extracted with 200 mL of ether. The ethereal solution was
washed with 200 mL of water, aqueous NaHCO3, and then
with water. After drying over anhydrous MgSO4, the solvent
was removed under reduced pressure, and the residue was
distilled (170-180 °C/1 mmHg). The distillate was a mixture
of trans- and cis-3-chloro-2-(p-chlorophenyl)propenenitrile.
trans-3-Chloro-2-(p-chlorophenyl)propenenitrile: 1H NMR
(CDCl3) δ 7.49-7.41 (m, 4H), 7.17 (s, 1H). cis-3-Chloro-2-(p-
chlorophenyl)propenenitrile:1H NMR (CDCl3) δ 7.67-7.61 (m,
4H), 7.22 (s, 1H).
P r ep a r a tion of 2-(p-Ch lor op h en yl)-4-d ia zo-4-p h en yl-
cis-2-bu ten en itr ile (1a ). To a stirred solution of phenyldia-
zomethane (5.21 g, 0.044 mol) and triethylamine (6.07 g, 0.06
mol) in 10 mL of dry CH2Cl2 in an ice bath was added all at
once the solution of trans- and cis-3-chloro-2-(p-chlorophenyl)-
propenenitrile (7.92 g, 0.04 mol) in 10 mL of CH2Cl2. After
stirring for 4 h, the reaction mixture was washed with 100
mL of water, and the separated CH2Cl2 layer was dried over
anhydrous MgSO4. The crude 2-(p-chlorophenyl)-4-diazo-4-
phenyl-cis-2-butenenitrile 1a was purified by column chroma-
tography on silica gel using benzene as an eluent and
Con clu sion s
The vinylcarbenoids derived from Rh2(OAc)4-catalyzed
decomposition of the vinyldiazo compounds 1a and 1b
attack the carbonyl oxygen atom of benzaldehydes 2 to
initially form the endo-vinyl-endo-aryl vinylcarbonyl
ylides 14 (15). The ylides 14 undergoes conrotatory
cyclization to the oxirane 3 and competitive rotation
around the C-O bond to isomerize to the ylides 16
followed by conrotatory cyclization to oxiranes 4 and
(20) Creary, X. Organic Syntheses; Wiley: New York, 1990; Collect.
Vol. VII, p 438.
(21) Diazoethane was prepared by
a procedure similar to the
synthetic method of diazomethane described in: Organic Syntheses;
Wiley: New York, 1943; Collect. Vol. II, p 165.
(22) Cariou, M. Bull. Soc. Chim. Fr. 1969, 217.
(18) Epiotis, N. D. J . Am. Chem. Soc. 1973, 95, 1200.
(19) Hayes, E. F.; Siu, A. K. Q. J . Am. Chem. Soc. 1971, 93, 2090.

5402 J . Org. Chem., Vol. 66, No. 16, 2001
Hamaguchi et al.
recrystallized from CH2Cl2/ether: dark red needles; mp 93.0
°C (decomp); H NMR (CDCl3) δ 7.57-7.30 (m, 3H), 7.48 (d,
2H, J ) 8.6 Hz), 7.38 (d, 2H, J ) 8.6 Hz), 7.18-7.15 (m, 2H),
7.07 (s, 1H); IR (KBr) 2204, 2052, 1597, 1575, 1562, 1496, 1318,
1253, 1101, 825, 746, 688 cm-1. Anal. Calcd for C16H10ClN3:
C, 68.70; H, 3.60; N, 15.02; Found: C, 68.86; H, 3.78; N, 15.02.
3-(p-Ch lor op h en yl)-tr a n s-2-m esityl-5-p h en yl-2,3-d ih y-
d r o-3-fu r a n ca r bon itr ile (5b): 14% yield; white needles; mp
166.1-166.4 °C; 1H NMR (CDCl3) δ 7.74-7.71 (m, 2H), 7.46-
7.43 (m, 3H), 7.08 (br s, 4H), 6.77 (s, 1H), 6.67 (br s, 2H), 5.82
(s, 1H), 2.70 (br s, 3H), 2.19 (s, 3H), 1.80 (br s, 3H); IR (KBr)
3107, 2922, 2231, 1784, 1647, 1612, 1491, 1282, 1093, 1014,
822, 752 cm-1. Anal. Calcd for C26H22ClNO: C, 78.09; H, 5.54;
N, 3.50. Found: C, 78.03; H, 5.67; N, 3.55.
1
P r ep a r a tion of 2-(p-Ch lor op h en yl)-4-d ia zo-cis-2-p en -
ten en itr ile (1b). To the stirred ethereal solution of diazo-
ethane (0.044 mol) and triethylamine (6.07 g, 0.06 mol) in an
ice bath was added dropwise the solution of trans- and cis-3-
chloro-2-(p-chlorophenyl)-propenenitrile (7.92 g, 0.04 mol) in
10 mL of CH2Cl2. After stirring for 2 h, the reaction mixture
was washed with 100 mL of water, and the separated CH2Cl2
layer was dried over anhydrous MgSO4. The crude 2-(p-
chlorophenyl)-4-diazo-cis-2-pentenenitrile 1b was purified by
column chromatography on silica gel using benzene as an
eluent and recrystallized from CH2Cl2/ether: orange powders;
mp 92.6 °C (decomposition); 1H NMR (CDCl3) δ 7.40-7.30 (m,
4H), 6.89 (s, 1H), 2.36 (s, 3H); IR (KBr) 3043, 2201, 2059, 1574,
1494, 1372, 1283, 1205, 1098, 826 cm-1. Anal. Calcd for C11H8-
ClN3: C, 60.70; H, 3.70; N, 19.31. Found: C, 60.87; H, 4.06;
N, 19.20.
Gen er a l P r oced u r e for Rea ction of 1a , 1b w ith Su b-
stitu ted Ben za ld eh yd es. A substituted benzaldehyde (5
mmol) and a catalytic amount of Rh2(OAc)4 was dissolved in
10 mL of dry benzene. The solution of 1a (1 mmol) in 4 mL of
dry benzene was added over 1 h to the above stirring solution
at 50 °C in an argon atmosphere. Stirring was continued until
the evolution of nitrogen ceased. The reaction mixture was
purified by column chromatography on silica gel using benzene
as an eluent, giving (Z)-vinyloxirane 3, (E)-vinyloxirane 4, (E)-
dihydrofuran 5, and (Z)-dihydrofuran 6) as crystals. These
products were recrystallized from CH2Cl2/ether.
Rea ction of 1a w ith p-Ch lor oben za ld eh yd e (2c). 3,4-
E p oxy-1-(p -ch lor op h en yl)-tr a n s-4-(p -ch lor op h en yl)-3-
p h en yl-(Z)-bu ten en itr ile (3c): 15% yield; white needles; mp
1
115.2-116.0 °C; H NMR (CDCl3) δ 7.54 (d, 2H, J ) 8.9 Hz),
7.40 (d, 2H, J ) 8.9 Hz), 7.36-7.32 (m, 2H), 7.28-7.22 (m,
3H), 7.15 (s, 4H), 7.11 (s, 1H), 4.70 (s, 1H); 13C NMR (CDCl3)
δ 142.61 (d), 136.15 (s), 133.92 (s), 133.37 (s), 132.17 (s), 130.64
(d), 129.33 (d), 128.66 (d), 128.48 (d), 128.12 (d), 128.10 (d),
127.59 (d), 127.31 (d), 116.28 (d), 115.84 (t), 66.61 (s), 65.57
(d); IR (KBr) 2225, 1893, 1595, 1446, 1418, 1333, 1098, 987,
868 cm-1. Anal. Calcd for C23H15Cl2NO: C, 70.42; H, 3.85; N,
3.57. Found: C, 70.35; H, 3.99; N, 3.57.
3,4-Ep oxy-1-(p-ch lor op h en yl)-cis-4-(p-ch lor op h en yl)-3-
p h en yl-(Z)-bu ten en itr ile (4c): 42% yield; colorless cubes; mp
159.0-160.5 °C; 1H NMR (CDCl3) δ 7.54-7.51 (m, 2H), 7.48-
7.39 (m, 3H), 7.37-7.29 (m, 4H), 7.32 (br s, 4H), 6.83 (s, 1H),
4.32 (s, 1H); 13C NMR (CDCl3) δ 138.41 (d), 136.82 (s), 136.14
(s), 134.36 (s), 132.47 (s), 130.79 (s), 129.29 (d), 128.89 (d),
128.82 (d), 128.42 (d), 128.26 (d), 127.06 (d), 125.93 (d), 120.03
(s), 115.51 (d), 67.62 (d), 65.32 (s); IR (KBr) 2224, 1614, 1445,
1326, 1303, 1094, 963, 823 cm-1. Anal. Calcd for C23H15Cl2-
NO: C, 70.42; H, 3.85; N, 3.57. Found: C, 70.35; H, 3.90; N,
3.55.
tr a n s-2,3-Di-(p-ch lor op h en yl)-5-p h en yl-2,3-d ih yd r o-3-
fu r a n ca r bon itr ile (5c): 27% yield; colorless cubes; mp 139.9-
141.0 °C; 1H NMR (CDCl3) δ 7.77-7.73 (m, 2H), 7.49-7.46
(m, 3H), 7.15-7.08 (m, 8H), 6.18 (s, 1H), 5.71 (s, 1H); 13C NMR
(CDCl3) δ 160.07 (s), 134.59 (s), 134.53 (s), 132.54 (s), 132.26
(s), 130.45 (d), 128.76 (d), 128.58 (d), 128.37 (d), 127.66 (d),
125.92 (d), 120.89 (d), 97.68 (d), 90.75 (d), 55.65 (s); IR (KBr)
Rea ction of 1a w ith p-An isa ld eh yd e (2a ). 3,4-Ep oxy-
1-(p-ch lor op h en yl)-tr a n s-4-(p-m eth oxyp h en yl)-3-p h en yl-
(Z)-bu ten en itr ile (3a ): 26% yield; white cubes; mp 145.2-
145.5 °C; 1H NMR (CDCl3) δ 7.53 (d, 2H, J ) 8.6 Hz), 7.39 (d,
2H, J ) 8.6 Hz), 7.36-7.34 (m, 2H), 7.24-7.23 (m, 3H), 7.11
(s, 1H), 7.10 (d, 2H, J ) 8.9 Hz), 6.70 (d, 2H, J ) 8.9 Hz), 4.66
(s, 1H), 3.72 (s, 3H); IR (KBr) 3062, 3016, 2227, 1612, 1518,
1495, 1254, 1176, 1095, 1032, 1014, 893, 829, 700 cm-1. Anal.
Calcd for C24H18ClNO2: C, 74.32; H, 4.68; N, 3.61. Found: C,
73.99; H, 4.80; N, 3.60.
2235, 1635, 1575, 1449, 1403, 1327, 1231, 1030, 982, 876 cm-1
.
Anal. Calcd for C23H15Cl2NO: C, 70.42; H, 3.85; N, 3.57.
Found: C, 70.30; H, 3.98; N, 3.62.
Rea ction of 1a w ith p-Nitr oben za ld eh yd e (2d ). 3,4-
Epoxy-1-(p-ch lor oph en yl)-tr a n s-4-(p-n itr oph en yl)-3-ph en -
yl-(Z)-bu ten en itr ile (3d ): 11% yield; white needles; mp
3,4-Epoxy-1-(p-ch lor oph en yl)-cis-4-(p-m eth oxyph en yl)-
3-p h en yl-(Z)-bu ten en itr ile (4a ): 25% yield; pale yellow oil;
1H NMR (CDCl3) δ 7.54-7.51 (m, 2H), 7.45-7.37 (m, 3H), 7.32
(s, 4H), 7.28 (d, 2H, J ) 8.6 Hz), 6.87 (d, 2H, J ) 8.6 Hz), 6.85
(s, 1H), 4.29 (s, 1H), 3.79 (s, 3H); IR (KBr) 3060, 2964, 2225,
1
160.5-161.2 °C; H NMR (CDCl3) δ 8.04 (d, 2H, J ) 8.9 Hz),
7.56 (d, 2H, J ) 8.9 Hz), 7.43 (d, 2H, J ) 8.6 Hz), 7.41 (d, 2H,
J ) 8.6 Hz), 7.36-7.33 (m, 2H), 7.25-7.23 (m, 3H), 7.13 (s,
1H), 4.84 (s, 1H); IR (KBr) 3043, 2225, 1606, 1531, 1495, 1348,
1099, 1014, 827, 700 cm-1. Anal. Calcd for C23H15ClN2O3: C,
68.58; H, 3.75; N, 6.95. Found: C, 68.23; H, 3.85; N, 6.91.
3,4-Ep oxy-1-(p-ch lor op h en yl)-cis-4-(p-n itr op h en yl)-3-
p h en yl-(Z)-bu ten en itr ile (4d ): 13% yield; white needles; mp
1613, 1515, 1493, 1251, 1174, 1096, 1032, 1013, 827, 698 cm-1
HRMS calcd for C24H18O2NCl: 387.1026; found: 387.1028.
;
3-(p-Ch lor oph en yl)-tr a n s-2-(p-m eth oxyph en yl)-5-ph en -
yl-2,3-d ih yd r o-3-fu r a n ca r bon itr ile (5a ): 36% yield; color-
less cubes; mp 137.2-137.8 °C; 1H NMR (CDCl3) δ 7.77-7.74
(m, 2H), 7.47-7.45 (m, 3H), 7.11 (d, 2H, J ) 8.6 Hz), 7.04 (d,
2H, J ) 8.6 Hz), 6.99 (d, 2H, J ) 8.9 Hz), 6.67 (d, 2H, J ) 8.9
Hz), 6.16 (s, 1H), 5.70 (s, 1H), 3.73 (s, 3H); IR (KBr) 3052, 2960,
1
145.3-145.8 °C; H NMR (CDCl3) δ 8.22 (d, 2H, J ) 8.6 Hz),
7.57 (d, 2H, J ) 8.9 Hz), 7.55-7.51 (m, 2H), 7.50-7.42 (m,
3H), 7.33 (ABq, 4H, J ) 9.2 Hz), 6.84 (s, 1H), 4.45 (s, 1H); 13
C
NMR (CDCl3) δ 147.86 (s), 141.18 (s), 137.29 (d), 136.49 (s),
136.23 (s), 130.30 (s), 129.42 (d), 129.16 (s), 129.04 (d), 127.94
(d), 127.02 (d), 125.94 (d), 123.39 (d), 120.31 (t), 115.43 (d),
67.26 (d), 65.96 (s); IR (KBr) 3060, 2233, 1603, 1522, 1493,
2237, 1637, 1614, 1516, 1491, 1281, 1252, 1016, 829, 750 cm-1
.
Anal. Calcd for C24H18ClNO2: C, 74.32; H, 4.68; N, 3.61.
Found: C, 74.37; H, 4.81; N, 3.69.
1348, 1095, 1012, 827, 700 cm-1. Anal. Calcd for C23H15
-
Rea ction of 1a w ith Mesita ld eh yd e (2b). 3,4-Ep oxy-1-
(p-ch lor op h en yl)-tr a n s-4-m esityl-3-p h en yl-(Z)-bu ten en i-
tr ile (3b): 7% yield; white needles; mp 131.7-132.5 °C; 1H
NMR (CDCl3) δ 7.59 (d, 2H, J ) 8.6 Hz), 7.42 (d, 2H, J ) 8.6
Hz), 7.37 (s, 1H), 7.22-7.16 (m, 5H), 6.65 (s, 2H), 4.61 (s, 1H),
2.31 (br s, 6H), 2.16 (s, 3H); IR (KBr) 2224, 1610, 1491, 1447,
1405, 1096, 1013 cm-1. Anal. Calcd for C26H22ClNO: C, 78.09;
H, 5.54; N, 3.50. Found: C, 77.57; H, 5.65; N, 3.52.
3,4-E p oxy-1-(p -ch lor op h en yl)-cis-4-m esit yl-3-p h en yl-
(Z)-bu ten en itr ile (4b): 18% yield; colorless cubes; mp 113.7-
114.3 °C; 1H NMR (CDCl3) δ 7.62-7.58 (m, 2H), 7.46-7.43
(m, 3H), 7.27 (d, 2H, J ) 8.6 Hz), 7.14 (d, 2H, J ) 8.6 Hz),
6.84 (s, 2H), 6.66 (s, 1H), 4.27 (s, 1H), 2.43 (br s, 6H), 2.26 (s,
3H); IR (KBr) 2224, 1609, 1450, 1404, 1095, 1011 cm-1. Anal.
Calcd for C26H22ClNO: C, 78.09; H, 5.54; N, 3.50. Found: C,
78.03; H, 5.69; N, 3.56.
ClN2O3: C, 68.58; H, 3.75; N, 6.95. Found: C, 68.41; H, 3.90;
N, 6.94.
3-(p-Ch lor op h en yl)-tr a n s-2-(p-n itr op h en yl)-5-p h en yl-
2,3-d ih yd r o-3-fu r a n ca r bon itr ile (5d ): 39% yield; colorless
1
cubes; mp 182.2-182.6 °C; H NMR (CDCl3) δ 8.04 (d, 2H, J
) 8.6 Hz), 7.78-7.75 (m, 2H), 7.52-7.48 (m, 3H), 7.35 (d, 2H,
J ) 8.6 Hz), 7.12 (d, 2H, J ) 8.9 Hz), 7.07 (d, 2H, J ) 8.9 Hz),
6.30 (s, 1H), 5.74 (s, 1H); 13C NMR (CDCl3) δ 160.00 (s), 147.78
(s), 141.26 (s), 134.94 (s), 131.70 (s), 130.67 (d), 128.84 (d),
128.81 (d), 128.54 (d), 128.02 (s), 127.13 (d), 125.94 (d), 123.35
(d), 120.46 (d), 97.87 (d), 90.04 (d), 55.78 (s); IR (KBr) 3122,
3082, 2252, 1643, 1604, 1525, 1491, 1348, 1282, 1012, 746, 737
cm-1. Anal. Calcd for C23H15ClN2O3: C, 68.58; H, 3.75; N, 6.95.
Found: C, 68.36; H, 3.91; N, 6.90.
3-(p-Ch lor op h en yl)-cis-2-(p-n itr op h en yl)-5-p h en yl-2,3-
d ih yd r o-3-fu r a n ca r bon itr ile (6d ): 5% yield; colorless cubes;

Reaction of Vinylcarbenoids with Benzaldehydes
J . Org. Chem., Vol. 66, No. 16, 2001 5403
1
mp 191.9-192.1 °C; H NMR (CDCl3) δ 8.30 (d, 2H, J ) 8.9
3,4-Epoxy-1-(p-ch lor oph en yl)-tr a n s-4-(p-ch lor oph en yl)-
3-m eth yl-(Z)-bu ten en itr ile(7c): 14% yield; white needles;
mp 112.0-112.9 °C; H NMR (CDCl3) δ 7.53 (d, 2H, J ) 8.6
Hz), 7.76-7.72 (m, 2H), 7.51-7.47 (m, 9H), 5.65 (s, 1H), 5.62
(s, 1H); 13C NMR (CDCl3) δ 160.59 (s), 148.56 (s), 141.99 (s),
136.15 (s), 135.36 (s), 130.66 (d), 129.63 (d), 128.79 (d), 128.21
(s), 127.91 (s), 127.33 (d), 125.99 (d), 123.96 (d), 117.65 (d),
97.02 (d), 92.82 (d), 59.09 (s); IR (KBr) 3105, 3070, 2229, 1647,
1606, 1523, 1491, 1348, 1059, 1012, 742, 725 cm-1. Anal. Calcd
for C23H15ClN2O3: C, 68.58; H, 3.75; N, 6.95. Found: C, 68.25;
H, 3.70; N, 6.98.
1
Hz), 7.42 (d, 2H, J ) 8.6 Hz), 7.39 (s, 4H), 6.97 (s, 1H), 4.28 (s,
1H), 1.36 (s, 3H); IR (KBr) 3043, 2225, 1606, 1531, 1495, 1348,
1099, 1014, 827, 700 cm-1. Anal. Calcd for C18H13Cl2NO: C,
65.47; H, 3.97; N, 4.24. Found: C, 65.51; H, 4.01; N, 4.20.
3,4-Ep oxy-1-(p-ch lor op h en yl)-cis-4-(p-ch lor op h en yl)-3-
m eth yl-(Z)-bu ten en itr ile(8c): 54% yield; colorless cubes; mp
1
R ea ct ion of 1a w it h 2,4-Din it r ob en za ld eh yd e (2e).
3-(p-Ch lor op h en yl)-tr a n s-2-(2,4-d in itr op h en yl)-5-p h en yl-
2,3-d ih yd r o-3-fu r a n ca r bon itr ile (5e): 20% yield; colorless
cubes; mp 182.4-182.9 °C;1H NMR (CDCl3) δ 8.74 (d, 1H, J )
2.3 Hz), 8.32 (dd, 1H, J ) 2.3, 8.9 Hz), 7.76 (d, 1H, J ) 8.9
Hz), 7.76-7.74 (m, 2H), 7.52-7.49 (m, 3H), 7.17 (d, 2H, J )
110.0-110.9 °C; H NMR (CDCl3) δ 7.32 (d, 2H, J ) 8.6 Hz),
7.25 (d, 2H, J ) 8.6 Hz), 7.26 (s, 4H), 6.59 (s, 1H), 4.15 (s,
1H), 1.82 (s, 3H); IR (KBr) 2980, 2227, 1600, 1493, 1405, 1375,
1332, 1092, 1053, 1013, 834, 824 cm-1. Anal. Calcd for C18H13
-
Cl2NO: C, 65.47; H, 3.97; N, 4.24. Found: C, 65.53; H, 4.05;
N, 4.24.
tr a n s-2,3-Di-(p-ch lor op h en yl)-5-m eth yl-2,3-d ih yd r o-3-
fu r a n ca r bon itr ile (9c): 1H NMR (CDCl3) δ 7.13 (d, 2H, J )
8.6 Hz), 7.10 (d, 2H, J ) 8.6 Hz), 7.01-6.59 (m, 4H), 6.00 (s,
1H), 5.03 (s, 1H), 2.15 (s, 3H).
8.6 Hz), 7.15 (s, 1H), 7.07 (d, 2H, J ) 8.6 Hz), 5.57 (s, 1H); 13
C
NMR (CDCl3) δ 159.49 (s), 147.68 (s), 146.39 (s), 139.21 (s),
135.21 (s), 132.30 (d), 130.90 (d), 130.52 (d), 129.11 (d), 128.99
(d), 128.66 (d), 127.69 (s), 127.44 (d), 125.96 (d), 120.43 (s),
120.24 (d), 96.89 (d), 85.99 (d), 56.75 (s); IR (KBr) 3111, 2243,
1655, 1608, 1537, 1493, 1350, 1063, 1020, 831, 735 cm-1. Anal.
Calcd for C23H14ClN3O5: C, 61.69; H, 3.15; N, 9.38. Found: C,
61.29; H, 3.22; N, 9.24.
Rea ction of 2-(p-Ch lor op h en yl)-4-d ia zo-cis-2-p en ten e-
n itr ile (1b) w ith p-Nitr oben za ld eh yd e (2d ). The reaction
was carried out in a procedure described above. (E)-vinyl-
oxirane (8d ) was recrystallized from CH2Cl2/ether.
3,4-Ep oxy-1-(p-ch lor op h en yl)-cis-4-(p-n itr op h en yl)-3-
m eth yl-(Z)-bu ten en itr ile (8d ): 65% yield; colorless cubes;
3-(p-Ch lor op h en yl)-cis-2-(2,4-d in itr op h en yl)-5-p h en yl-
2,3-d ih yd r o-3-fu r a n ca r bon itr ile (6e): 32% yield; white
needles; mp 168.9-169.7 °C;1H NMR (CDCl3) δ 9.06 (d, 2H, J
) 2.3 Hz), 8.56 (dd, 1H, J ) 2.3, 8.6 Hz), 7.91 (d, 1H, J ) 8.6
Hz), 7.77-7.74 (m, 2H), 7.56 (d, 2H, J ) 8.6 Hz), 7.53-7.47
1
mp 125.3-126.2 °C; H NMR (CDCl3) δ 8.17 (d, 2H, J ) 8.9
Hz), 7.50 (d, 2H. J ) 8.9 Hz), 7.32 (d, 2H, J ) 8.9 Hz), 7.23 (d,
2H, J ) 8.9 Hz), 6.63 (s, 1H), 4.27 (s, 1H), 1.86 (s, 3H); IR
(KBr) 3108, 2222, 1603, 1516, 1493, 1346, 1101, 1012, 849,
831, 706 cm-1. Anal. Calcd for C18H13ClN2O3: C, 63.44; H, 3.85;
N, 8.22. Found: C, 63.32; H, 3.94; N, 8.20.
(m, 3H), 7.44 (d, 2H, J ) 8.6 Hz), 6.42 (s, 1H), 5.63 (s, 1H); 13
C
NMR (CDCl3) δ 158.45 (s), 148.18 (s), 147.14 (s), 139.87 (s),
137.00 (s), 135.10 (s), 130.93 (d), 129.47 (d), 129.39 (d), 129.04
(d), 128.28 (d), 127.40 (s), 127.33 (d), 125.94 (d), 120.80 (s),
117.32 (s), 98.87 (d), 87.86 (d), 59.13 (s); IR (KBr) 3109, 2247,
1649, 1608, 1537, 1493, 1350, 1032, 833, 733 cm-1. Anal. Calcd
for C23H14ClN3O5: C, 61.69; H, 3.15; N, 9.38. Found: C, 61.77;
H, 3.39; N, 9.21.
Rea ction of 1a w ith p-Ch lor oben za ld eh yd e (2c) in th e
P r esen ce of Maleic An h ydr ide. p-Chlorobenzaldehyde (0.702
g, 5 mmol), maleic anhydride (0.490 g, 5 mmol), and a catalytic
amount of Rh2(OAc)4 was dissolved in 10 mL of dry dichloro-
ethane. The solution of 1a (0.280 g, 1 mmol) in 4 mL of dry
dichloroethane was added over 1 h to the above stirring
solution at 0 °C in an argon atmosphere. Stirring was
continued until the evolution of nitrogen ceased. Unreacted
p-chlorobenzaldehyde and maleic anhydride were removed
from the reaction mixture under reduced pressure. The residue
was crystallized from CH2Cl2 to give 2c-p-chlorophenyl-5c-[â-
cyano-p-chlorostyryl]-5t-phenyl-tetrahydro-3r,4c-furandicar-
boxylic anhydride 11c: 71% yield; colorless cubes; mp 239.5-
239.9 °C; 1H NMR (CDCl3) δ 7.62-7.58 (m, 2H), 7.54-7.35
(m, 11H), 7.03 (s, 1H), 5.28 (d, 1H, J ) 8.3 Hz), 4.53 (d, 1H, J
) 8.3 Hz), 3.81 (t, 1H, J ) 8.3 Hz); IR (KBr) 3434, 3062, 2225,
Rea ction of 2-(p-Ch lor op h en yl)-4-d ia zo-cis-2-p en ten e-
n itr ile (1b) w ith p-An isa ld eh yd e (2a ). The solution of 1b
(0.218 g, 1 mmol) in 4 mL of dry benzene was added over 1 h
to the stirring solution of p-anisaldehyde (0.681 g, 5 mmol)
and a catalytic amount of Rh2(OAc)4 in 10 mL of dry benzene
at 50 °C in an argon atmosphere. Stirring was continued until
the evolution of nitrogen ceased. Unreacted p-anisaldehyde
was removed from the reaction mixture under reduced pres-
sure. The reaction mixture was purified by column chroma-
tography on silica gel. Elution with benzene gave (Z)-
vinyloxirane 7a and (E)-vinyloxirane 8a .
1861, 1786, 1597, 1493, 1215, 1088, 1041, 953, 918, 825 cm-1
.
3,4-E p oxy-1-(p -ch lor op h e n yl)-t r a n s-4-(p -m e t h oxy-
p h en yl)-3-m eth yl-(Z)-bu ten en itr ile (7a ): 37% yield; pale
yellow oil; H NMR (CDCl3) δ 7.52 (d, 2H, J ) 8.6 Hz), 7.35
Anal. Calcd for C27H17Cl2NO4: C, 66.14; H, 3.49; N, 2.86.
Found: C, 66.04; H, 3.56; N, 2.72.
1
(d, 2H. J ) 8.9 Hz), 7.39 (d, 2H, J ) 8.6 Hz), 6.96 (s, 1H), 6.61
(d, 2H, J ) 8.9 Hz), 4.25 (s, 1H), 3.82 (s, 3H), 1.38 (s, 3H); IR
(KBr) 2962, 2933, 2837, 2222, 1616, 1515, 1493, 1250, 1173,
1096, 1034, 829 cm-1; HRMS calcd for C19H16O2NCl 325.0870,
found 325.0863.
3,4-Epoxy-1-(p-ch lor oph en yl)-cis-4-(p-m eth oxyph en yl)-
3-m eth yl-(Z)-bu ten en itr ile (8a ): 36% yield; pale yellow oil;
1H NMR (CDCl3) δ 7.27 (ABq, 4H, J ) 8.6 Hz), 7.21 (d, 2H. J
) 8.9 Hz), 6.83 (d, 2H, J ) 8.9 Hz), 6.61 (s, 1H), 4.13 (s, 1H),
3.76 (s, 3H), 1.81 (s, 3H); IR (KBr) 2965, 2931, 2837, 2223,
1613, 1516, 1493, 1251, 1173, 1096, 1034, 829 cm-1; HRMS
calcd for C19H16O2NCl 325.0870, found 325.0868.
Rea ction 1b w ith p-Ch lor oben za ld eh yd e (2c). The
solution of 1b (0.218 g, 1 mmol) in 4 mL of dry benzene was
added over 1 h to the stirring solution of p-chlorobenzaldehyde
(0.702 g, 5 mmol) and a catalytic amount of Rh2(OAc)4 in 10
mL of dry benzene at 50 °C in an argon atmosphere. Stirring
was continued until the evolution of nitrogen ceased. Unre-
acted p-chlorobenzaldehyde was removed from the reaction
mixture under reduced pressure. NMR spectrum of the reac-
tion mixture showed (Z)-vinyloxirane 7c, (E)-vinyloxirane 8c,
and (E)-dihydrofuran 9c in a ratio of 16:82:2. The reaction
mixture was purified by column chromatography on silica gel.
Elution with benzene gave 7c and 8c. These products were
recrystallized from CH2Cl2/ether. (E)-Dihydrofuran (9c) could
not be isolated.
Rea ction of 1b w ith p-Ch lor oben za ld eh yd e in th e
P r esen ce of Ma leic An h yd r id e. A solution of 1b (0.218 g, 1
mmol) in 4 mL of dry dichloroethane was added over 1 h to a
stirred solution of p-chlorobenzaldehyde (0.702 g, 5 mmol),
maleic anhydride (0.490 g, 5 mmol), and a catalytic amount
of Rh2(OAc)4 in 10 mL of dry dichloroethane at 0 °C in an argon
atmosphere. Stirring was continued until the evolution of
nitrogen ceased. Unreacted p-chlorobenzaldehyde and maleic
anhydride were removed from the reaction mixture under
reduced pressure. The residue was crystallized from CH2Cl2
to give 2c-p-chlorophenyl-5c-[â-cyano-p-chlorostyryl]-5t-methyl-
tetrahydro-3r,4c-furandicarboxylic anhydride 12c: 68% yield;
1
colorless cubes; mp 210.2-211.0 °C; H NMR (CDCl3) δ 7.58
(d, 2H, J ) 8.6 Hz), 7.43 (d, 2H, J ) 8.6 Hz), 7.40 (s, 4H), 7.03
(s, 1H), 5.57 (d, 1H, J ) 8.3 Hz), 3.99 (t, 1H, J ) 8.3 Hz), 3.90
(d, 1H, J ) 8.3 Hz), 1.18 (s, 3H); IR (KBr) 3064, 2225, 1865,
1784, 1595, 1495, 1203, 1093, 935, 910, 827 cm-1. Anal. Calcd
for C22H15Cl2NO4: C, 61.70; H, 3.53; N, 3.27. Found: C, 61.81;
H, 3.59; N, 3.37.
Rea ction of 1a w ith p-Ch lor oben za ld eh yd e (2c) in th e
P r esen ce of Dim eth yl F u m a r a te. The reaction was carried
out in a procedure described above. NMR spectrum of the
reaction mixture showed 3a , 4a , 5a , and cycloadduct 13c in a
ratio of 17:24:11:48. The reaction mixture was purified by
column chromatography on silica gel using benzene as an
eluent, giving dimethyl 2t-p-chlorophenyl-5t-[â-cyano-p-chloro-

5404 J . Org. Chem., Vol. 66, No. 16, 2001
Hamaguchi et al.
styryl]-5c-phenyl-tetrahydro-3r,4t-furandicarboxylate 13c re-
(dd, 1H, J ) 7.6, 9.2 Hz), 3.76 (s, 3H), 3.59 (s, 3H); IR (KBr)
2954, 2222, 1744, 1730, 1492, 1438, 1258, 1245, 1169, 1049,
1012, 826, 706 cm-1. Anal. Calcd for C29H23Cl2NO5: C, 64.94;
H, 4.32; N, 2.61. Found: C, 64.734; H, 4.37; N, 2.58.
crystallized from CH2Cl2: 39% yield; colorless cubes; mp
1
124.0-124.9 °C; H NMR (CDCl3) δ 7.70-7.66 (m, 2H), 7.63
(d, 2H, J ) 8.6 Hz), 7.48-7.40 (m, 3H), 7.41 (d, 2H, J ) 8.6
Hz), 7.39 (d, 2H, J ) 8.6 Hz), 7.36 (d, 2H, J ) 8.6 Hz), 6.78 (s,
1H), 5.07 (d, 1H, J ) 9.2 Hz), 4.31 (d, 1H, J ) 7.6 Hz), 3.80
J O015618L