Selective Synthesis of Tetrahydro Oxepines by Cu‐Catalyzed Condensations of Diazomalonates and gem‐Dialkyl Vinyl Oxetanes.

Thanks to an unprecedented gem‐dialkyl substituent effect, an efficient synthesis of tetrahydro oxepine derivatives is achieved by ring expansion of vinyl oxetanes using acceptor(−acceptor) diazo reagents under Cu(II)‐catalysis. A large scope of 2‐vinyl oxetanes and either diazo mono or diester reagents give access to a series of functionalized oxepines. [ABSTRACT FROM AUTHOR]