Me3SiBr-mediated intramolecular cyclization of γ-functionalized trimethylsilyl nitronates
作者:Alexander A Tishkov、Anton V Kozintsev、Il'ya M Lyapkalo、Sema L Ioffe、Vadim V Kachala、Yuri A Strelenko、Vladimir A Tartakovsky
DOI:10.1016/s0040-4039(99)00985-5
日期:1999.7
The silylation of nitro compounds of general formula X1X2CHCH(Ar)CH2NO2 with at −30°C leads to hitherto unknown 2-(N,N-bis(trimethylsilyloxy)amino-2,3-dihydrofurans (X1=PhCO, X2=H) or to N,N-bis(trimethylsilyloxy)aminocyclopropanes (X1=X2=COOMe). N,N-Bis(trimethylsilyloxy)immonium cations appear to be the key intermediates in this process.
的通式X的硝基化合物甲硅烷基化1 X 2 CHCH(Ar)的CH 2 NO 2与在-30℃通入迄今未知的2-(Ñ,Ñ双(三甲基甲硅烷基)氨基-2,3-二氢呋喃(X 1 = PhCO,X 2 = H)或N,N-双(三甲基甲硅烷氧基)氨基环丙烷(X 1 = X 2 = COOMe)N,N-双(三甲基甲硅烷氧基)铵阳离子似乎是该过程中的关键中间体。
——
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.