that the ester functionality could have a profound impact on
the course of this reaction. Hence, the benzylic position was
substituted R to the phenyl ring with methyl, ethyl, and
phenyl groups as shown in Table 2.
Table 1. Formation of R-Trialkylsilanyldioxolanones
Table 2. Effect of the Ester Functionality
diazo ester
R
product
yield (%)
1c
1d
1e
1f
H
Me
Et
3i
3j
3k
3l
84
78
81
92
Ph
These substituents at the R-position did not alter the
outcome of the reaction, and dioxolanones in up to 92% yield
were isolated. (R)-(+)-1-Phenylethanol was used for the
synthesis of 1d, and the dioxolanone cycloadduct 3j was
obtained in a diastereoselectivity of 3.5:1 due to the effect
of the chirality of the ester functionality.
Moreover, we investigated the influence of various sub-
stituents on the benzene ring as shown in Table 3. In the
case of the electron-donating methoxy group in the para
position as in 1g, dioxolanone 3m was formed exclusively.
However, contrary to our expectation, enolether 4a was
isolated in 73% yield when the methoxy group was replaced
by a nitro group. Interestingly, in the case of triflouromethyl
in the para position, a mixture of products 3n and 4b in a
ratio of 1:5 was obtained. Maas and Alt have observed the
formation of an enolether as the product of the Rh(II)-
catalyzed reaction involving trimethylsilyldiazoacetate, dim-
(4) (a) Kharasch, M. S.; Rudy, T.; Nudenberg, W.; Bu¨chi, G. J. Org.
Chem. 1953, 18, 1030. (b) Huisgen, R.; de March, P. J. Am. Chem. Soc.
1982, 104, 4953. (c) Alonso, M. E.; Garcia, M.-C.; Chitty, A. W. J. Org.
Chem. 1985, 50, 3445. (d) L’Esperance, R. P.; Ford, T. M.; Jones, M., Jr.
J. Am. Chem. Soc. 1988, 110, 209. (e) Lottes, A. C.; Landgrebe, J. A.;
Larsen, K. Tetrahedron Lett. 1989, 30, 4093. (f) Doyle, M. P.; Forbes, D.
C.; Protopopova, M. N.; Stanley, S. A.; Vasbinder, M. M.; Xavier, K. R.
J. Org. Chem. 1997, 62, 7210. (g) Hamaguchi, M.; Matsubara, H.; Nagai,
T. J. Org. Chem. 2001, 66, 5395. (h) Nakamura, Y.; Ukita, T. Org. Lett.
2002, 4, 2317.
Large groups in the R-position to the carbonyl group as in
2e and 2g only mildly hindered the cyclization process in
the case of 2e, and the desired dioxolanone 3e was formed
in a lower yield. The best result was achieved in the case of
the polycyclic adduct adamantanone 2h, which reacted
smoothly with benzyl trimethylsilyldiazoacetate to give 3h
in 98% yield. Interestingly, Maas and Alt have reported the
formation of dioxolanones in the dirhodium perflourobu-
tyrate-catalyzed reactions of allylic diazoacetates with various
aldehydes, including acetaldehyde, crotonaldehyde and aro-
matic aldehydes.9 Analogous to the reactions with aldehydes,
they also observed the formation of the corresponding
dioxolanone in the reaction with acetone. It occurred to us
(5) Jiang, B.; Zhang, X.; Luo, Z. Org. Lett. 2002, 4, 2453.
(6) (a) Hodgson, D. M.; Stupple, P. A.; Johnstone, C. Tetrahedron Lett.
1997, 38, 6471. (b) Hodgson, D. M.; Pierard, F. Y. T. M.; Stupple, P. A.
Chem. Soc. ReV. 2001, 30, 50.
(7) (a) Bolm, C.; Kasyan, A.; Drauz, K.; Gu¨nther, K.; Raabe, G. Angew.
Chem., Int. Ed. 2000, 39, 2288. (b) Bolm, C.; Kasyan, A.; Heider, P.;
Saladin, S.; Drauz, K.; Gu¨nther, K.; Wagner, C. Org. Lett. 2002, 4, 2265.
(8) Standard protocol for the catalysis: The corresponding trialkyl-
silyldiazo benzyl ester (1 mmol) was added dropwise under an argon
atmosphere to a stirring degassed solution of [Rh2(OAc)4] (8.8 mg, 0.02
mmol, 2 mol %) and the corresponding ketone (2 mmol) in dry toluene (8
mL) at room temperature. The reaction mixture was heated to 40 °C and
was left stirring at this temperature for 16 h. After the reaction mixture
was cooled to ambient temperature, the solvent was removed in vacuo, and
the crude product was purified by flash chromatography on silica gel or
Florisil (petroleum ether/tert-butyl methyl ether, various gradients).
(9) Maas, G.; Alt, M. Chem. Ber. 1994, 127, 1537.
4632
Org. Lett., Vol. 4, No. 26, 2002
Bolm, Carsten
