Diastereoselective synthesis of tetrahydrobenzobazocines by Lu(OTf)3-catalyzed 4+4 cycloaddition of donor–acceptor cyclobutanes with anthranils

摘要

The construction of N-heterocyclic eight-membered rings remains challenging due to unfavorable transannular strain. Herein, we report a Lu(OTf)3-catalyzed formal 4+4 cycloaddition reaction of cyclobutane 1,1-diesters with anthranils to deliver oxa-bridged eight-membered heterocycles. This methodology provides great potential to build complex azocine compounds from simple building blocks. Based on our preliminary mechanism studies, a probable mechanism for this annulation pathway has been proposed.