Reactions of phosphines with acetylenes. Part XVI. Formation of β-alkoxyphosphonium ylides and vinyl ethers via methanolysis of vinylphosphonium salts
作者:Ian F. Wilson、John C. Tebby
DOI:10.1039/p19720002830
日期:——
stabilised β-alkoxy-ylide, (b) with methyl phenylpropiolate to give (Z)-methyl 2-methoxycinnamate, and (c) with methyl propiolate to give a mixture of three isomeric methyl methoxyacrylates. The reactions proceed via nucleophilic attack of the phosphine on the acetylene and then of methoxide on the intermediate vinylphosphonium salt by the pathway which involves least build up of negative charge. Methoxide
三苯基膦在醇反应(一)与乙炔二,得到稳定化的β -烷氧基叶立德,(b)用甲基苯基丙得到(ż)-2-甲氧基,和(C ^)与丙炔酸甲酯,得到三种混合物异构体甲氧基丙烯酸甲酯。该反应通过膦在乙炔上的亲核攻击,然后通过中间体中乙烯基phosph盐的甲醇盐的亲核攻击,通过最小程度地积累负电荷的途径进行。当带有the基团的乙烯基α-碳原子具有另一个稳定基团时,例如(a)中的甲氧基羰基,甲醇盐会攻击β-碳原子)或(b)中的苯基。当(c)中有稳定的α和β稳定基团时,甲醇氧化物会攻击α和β位置。反应(b)和(c)涉及两个反式加成步骤,然后是反式消除步骤。