5-Formyl- and 5-acetyl-4-(alkenylamino)pyrimidines 5 have been prepared as precursors to novel pyrimido[1,4]diazepine N-oxides 3. In addition to cyclisation to the targeted dipoles the substrates 5 have also been observed to form imidazopyrimidines 12 and 39via an intramolecular Michael addition; additionally 5b has been observed to form the pyrimidoazepinone 42. Aldonitrone 3a cycloadded readily to olefinic dipolarophiles; ketodipole 3b did not share this reactivity. Both dipoles reacted with acetylenic dipolarophiles but the ensuing cycloadducts 37 were unstable; facile ring contraction of their isoxazolopyrimidodiazepine skeletons to the pteridine nucleus is noted. The structure of 37c has been determined by X-ray crystallography.
Allyl diethyl phosphates (1) can be easily substituted with malonates and amines in the presence of palladium(O) catalyst. Synthetic utility of the reaction is demonstrated by the sequential amination-amination and alkylation-amination of (Z)-4-acetoxybut-2-enyl diethyl phosphate (1b) with high regio- and stereoselectivity.
Regiochemical control in the preparation of 2-(nosyloxy) .beta.,.gamma.-unsaturated esters and 4-(nosyloxy) .alpha.,.beta.-unsaturated esters from 1-[(trimethylsilyl)oxy]-1-alkoxy 1,3-dienes
作者:Robert V. Hoffman、Hwa Ok Kim
DOI:10.1021/jo00003a022
日期:1991.2
A series of 1-[(trialkylsilyl)oxy]-1-alkoxy 1,3-dienes 1a-i were found to react with p-nitrobenzenesulfonyl peroxide in the presence of sodium methoxide or zinc chloride to give alkyl 2-[[(p-nitrophenyl)sulfonyl]oxy] beta-gamma-unsaturated esters 3 and alkyl 4-[[(p-nitrophenyl)sulfonyl]oxy] alpha,beta-unsaturated esters 4 which are readily separable. The regioselectivity is determined by kinetic versus thermodynamic control. When positions 2 or 4 of the diene are unsubstituted, the 2-isomer is the major product and is the kinetically fastest formed product. It can be thermally rearranged to the more stable 4-isomer. When alkyl substituents are present at either the 2- or 4-positions, only the 4-isomer is obtained. Substitution for nosylate by amine nucleophiles occurs by an S(N)2 process. Thus 2-amino beta,gamma-unsaturated esters and 4-amino alpha,beta-unsaturated esters can be prepared from the appropriate starting nosylate.
A tandem radical cyclization approach to 3-(2-oxopyrrolidin-3-yl)indolin-2-ones, potential intermediates toward complex indole-heterocycles
A series of substituted 3-(2-oxopyrrolidin-3-yl)indolin-2-one derivatives have been synthesized by tris(trimethylsilyl)silane (TTMSS) induced tandem radical cyclization as key step. (c) 2007 Elsevier Ltd. All rights reserved.