名称:
                                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
                             
                            
                                摘要:
                                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.