Diastereofacial selectivity in ketene [2+2] cycloaddition to endocyclic enecarbamates bearing a chiral auxiliary. Synthesis of the (−)-Geissman-Waiss lactone
作者:Paulo Cesar M.L. Miranda、Carlos Roque D. Correia
DOI:10.1016/s0040-4039(99)01638-x
日期:1999.10
evaluated for the [2+2]cycloaddition with dichloroketenes. Diastereofacial selectivity ranged from zero (bornyl and menthyl) to 60% (Greene's auxiliary and 8-phenylmenthyl). Chromatography separation of the diastereomeric azacyclobutanones derived from the 8-phenylmenthyl enecarbamate permitted an enantiodivergent synthesis of the (−)-Geissman-Waiss lactone, a key intermediate in the synthesis of necine bases
用二氯乙烯酮对[2 + 2]环加成反应评估了带有手性助剂的烯甲酸酯的非对映选择性。非对面选择性的范围从零(冰片基和薄荷基)到60%(格林的助剂和8-苯基薄荷基)。色谱分离来自8-苯基薄荷基烯氨基甲酸酯的非对映体氮杂环丁酮,可以实现(-)-Geissman-Waiss内酯的对映异构体合成,这是合成烟碱的关键中间体。