Nazarov Cyclization and Tandem [4 + 2]-Cycloaddition Reactions of Donor–Acceptor Cyclopropanes
作者:Gangarajula Sudhakar、S. K. Mahesh、S. Phani Babu Vemulapalli、Jagadeesh Babu Nanubolu
DOI:10.1021/acs.orglett.7b02061
日期:2017.9.1
cyclopropanes (DACs) as novel Nazarov cyclization (NC) precursors is described. The 1,3-zwitterion, generated from DACs embedded in the divinyl framework, acts as a pentadienyl cation, a requisite for Nazarov cyclization. A cyclic allyl cation in the course of NC was trapped with external nucleophiles to provide an interrupted NC product. Indeed, an allyl cation in this reaction is analogous to a 1,4-zwitterion
描述了作为新型Nazarov环化(NC)前体的芳基乙烯基/二乙烯基供体-受体环丙烷(DAC)的开发。由嵌入二乙烯基框架中的DAC生成的1,3-两性离子可作为戊二烯基阳离子,这是Nazarov环化的必要条件。NC过程中的环状烯丙基阳离子被外部亲核试剂捕获,从而提供了中断的NC产物。实际上,此反应中的烯丙基阳离子类似于1,4-两性离子,与双极性亲和剂反应后,可通过NC进行正式的[4 + 2]环加成反应,从而轻松获得具有优良收率和非对映选择性的取代吡喃。