α-烃基甲氧羰基亚甲基三苯肿的合成及缩合反应

Synthesis and condensation reactions of α-alkyl substituted carbomethoxymethylene triphenylarsorane

由甲氧羰基亚甲基三苯胂(Ⅰ)和碘甲烷生成的碘化α-甲基甲氧羰基亚甲基三苯钟(Ⅱ)与甲醇钠作用后,可形成α-甲基甲氧羰基亚甲基三苯胂(Ⅲ)。而甲氧羰基亚甲基三苯胂(Ⅰ)与苄溴形成的溴化α-苄基钟盐(Ⅳ)可与另一分子甲氧羰基亚甲基三苯胂(Ⅰ)进行叶立德交换反应,形成α-苄基甲氧羰基亚甲基三苯肿(Ⅶ)。这些α-烃基取代的胂叶立德(Ⅲ)和(Ⅶ)均可与芳醛缩合并立体选择地生成芳基与酯基处于反位的三取代烯酸酯,水解后可得相应的烯酸。

Carbomethoxymethylene triphenylarsoranecan react with methyl iodide to give α-methylcarbomethoxymethylene triphenyl arsoniumiodide.The latter can be dehydrohalogenated bysodium methoxide to give α-methylcarbometh-oxymethylene triphenylarsorane.However,whencarbomethoxymethylene triphenylarsorane istreated with benzyl bromide at 60℃,thea-benzyl arsonium salt,that is formed first,can undergo transylidation with carbomethoxy-methylene triphenylarsorane to produce α-benzylcarbomethoxymethylene triphenylarsorane,The two new arsonium ylides can easily reactwith several aromatic aldehydes to give methylesters of the corresponding α,β-olefinic acid.These esters can be hydrolyzed to acids.Theadvantages of the method are the manipulativeconvenience and mild conditions of reaction.Inaddition,the method is stereospecific,in thiscase mainly E olefinic compounds are obtained(i.e.alkyl is opposite to carboxyl group).