methylketene can be conveniently prepared in one step and high enantiomeric excess from propionyl chloride, using a catalytic amount of a silylated cinchona alkaloid as a source of chirality. Opening of the dimer with a lithiated sulfonamide affords a β-ketosulfonimide, which undergoes Sn(II)-mediated aldol reactions to diastereoselectively afford the anti,syn-aldol adduct. Alternatively, reduction of the dimer
使用催化量的甲
硅烷基化的
金鸡纳
生物碱作为手性来源,可以方便地一步制备
甲基乙烯酮的二聚体,并由
丙酰氯制得高对映体过量。用
锂化的磺
酰胺打开二聚体得到β-
酮磺
酰亚胺,其经历Sn(II)介导的羟醛反应,非对映选择性地得到反式,顺式-羟醛加合物。或者,将二聚体还原为β-羟基
酮,然后进行酰化,得到β-酰
氧基
酮,其经历非对映选择性,二烷基
硼氯化物介导的醛醇缩合反应以产生抗,抗醛醇加合物。