作者:K. P. Birin
DOI:10.1023/a:1023958806825
日期:——
Silylation of gamma-nitro ketones of the general formula (RCOCH)-C-1(R-2)CH(R-3)CH(R-4)NO2 proceeded stereoselectively to give 2-[N,N-bis(trimethylsilyloxy)amino]-2,3-dihydrofurans, conjugated enoximes, silylation products of the carbonyl group or both functional groups, or N, N-bis(trimethylsilyloxy)enamine depending on the nature and positions of the substituents in the carbon skeleton. Dihydrofuran derivatives are formed for R-1 = Ar or cyclo-C3H5. Enoximes are generated as the silylation products of the starting ketones with enhanced P-proton mobility (R-3 CO2Me or 4-NO2C6H4). The presence of an alkyl group at the carbonyl function (R-1 = Alk) is favorable for the formation of enoximes. Finally, the introduction of a substituent at the a position with respect to the nitro group (R-4 = Me, CO2Me, or Ph) leads to the formation of silyl enolates. Under the action of NH4F in MeOH, dihydrofurans can be transformed into substituted furans in moderate yields.