Diastereoselective synthesis of tetrahydrobenzo[b]azocines by Lu(OTf)₃-catalyzed [4+4] cycloaddition of donor–acceptor cyclobutanes with anthranils

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.