ISSN 1070-4280, Russian Journal of Organic Chemistry, 2009, Vol. 45, No. 12, p. 1873. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © M.V. Dmitriev, P.S. Silaichev, A.N. Maslivets, 2009, published in Zhurnal Organicheskoi Khimii, 2009, Vol. 45, No. 12, p. 1874.
SHORT
COMMUNICATIONS
Regioselective [4+2]-Cycloaddition of Styrene to 4-Isopropoxalyl-
1H-pyrrole-2,3-diones
M. V. Dmitriev, P. S. Silaichev, and A. N. Maslivets
Perm State University, ul. Bukireva 15, Perm, 614990 Russia
e-mail: koh2@psu.ru
Received June 25, 2009
DOI: 10.1134/S1070428009120252
Reactions of 4-alkoxalyl-1H-pyrrole-2,3-diones
with alkenes were not reported previously. We have
found that isopropyl (1-aryl-4,5-dioxo-2-phenyl-4,5-
dihydro-1H-pyrrol-3-yl)oxoacetates Ia and Ib react
with styrene at a molar ratio of 1:1.5 on heating in
boiling anhydrous m-xylene (reaction time 15–16 h;
until disappearance of bright orange color typical of
initial pyrrolediones I) to give isopropyl 1-aryl-
1,2,3,6,7,7a-hexahydro-2,3-dioxo-6,7a-diphenyl-
pyrano[4,3-b]pyrrole-4-carboxylates IIa and IIb.
15 h under reflux. The mixture was cooled, and the
precipitate was filtered off and recrystallized from
ethyl acetate. Yield 87%, mp 240–242°C. IR spectrum,
ν, cm–1: 1728, 1701. 1H NMR spectrum, δ, ppm: 1.19 d
(3H, Me, J = 6.3 Hz), 1.28 d (3H, Me, J = 6.3 Hz),
2.62 t (1H, 7-H, J = 12.9 Hz), 2.69 d.d (1H, 7-H, J =
12.9, 3.6 Hz), 5.07 m (1H, CHMe2), 5.67 d.d (1H, 6-H,
J = 12.9, 3.6 Hz), 7.28–7.79 m (15H, Harom). Found, %:
C 74.41; H 5.35; N 2.97. C29H25NO5. Calculated, %:
C 74.50; H 5.39; N 3.00.
Isopropyl 1-(4-methoxyphenyl)-2,3-dioxo-6,7a-
diphenyl-1,2,3,6,7,7a-hexahydropyrano[4,3-b]pyr-
role-4-carboxylate (IIb) was synthesized in a similar
way. Yield 84%, mp 217–219°C (from toluene). IR
O
O
O
O
OPr-i
O
O
PhCH=CH2
i-PrO
O
1
spectrum, ν, cm–1: 1725, 1700. H NMR spectrum, δ,
Ph
O
N
N
Ph
ppm: 1.20 d (3H, Me, J = 6.2 Hz), 1.30 d (3H, Me, J =
6.2 Hz), 2.62 t (1H, 7-H, J = 12.9 Hz), 2.63 m (1H,
7-H), 3.77 s (3H, OMe), 5.06 m (1H, CHMe2), 5.63 m
(1H, 6-H), 7.03–7.80 m (14H, Harom). Found, %:
C 72.35; H 5.43; N 2.80. C30H27NO6. Calculated, %:
C 72.42; H 5.47; N 2.82.
Ph
Ar
Ar
Ia, Ib
IIa, IIb
Ar = Ph (a), 4-MeOC6H4 (b).
Presumably, compounds IIa and IIb are formed as
a result of thermally initiated [4+2]-cycloaddition of
the conjugated O=C–C=C bond system in pyrroles Ia
and Ib to the polarized exocyclic C=C bond in styrene
molecule.
The IR spectra were recorded on FSM-1201 (IIa)
and Specord 75IR spectrometers (IIb) from samples
1
dispersed in mineral oil. The H NMR spectra were
obtained on a Bruker AM-400 instrument at 400 MHz
using DMSO-d6 as solvent and tetramethylsilane as
internal reference.
Isopropyl 2,3-dioxo-1,6,7a-triphenyl-1,2,3,6,7,7a-
hexahydropyrano[4,3-b]pyrrole-4-carboxylate (IIa).
A solution of 1.5 mmol of styrene was added to
a solution of 1.0 mmol of compound Ia in 25 ml of
anhydrous m-xylene, and the mixture was heated for
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 08-03-01032).
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Dmitriev
