Transannular cyclizations of medium-sized cycloalkynes and cycloalkynones induced by electro- and photochemically generated NO3 radicals

Abstract

Transannular radical cyclizations of medium-sized cycloalkynes and cycloalkynones induced by addition of NO3 radicals to the C-C triple bond were studied. In the reaction of NO3• with medium-sized cycloalkynes oxidation of the triple bond to a carbonyl group occurred and formation of cis-fused bicyclic alkanones by transannular cyclization was observed. In the reaction of NO3 radicals with medium-sized cycloalkynones α,β-epoxy ketones were formed in a transannular reaction sequence which can be formally considered as a retro Eschenmoser-Ohloff fragmentation reaction. The scope and limitations of these reactions are presented and reaction mechanisms are proposed. © VCH Verlagsgesellschaft mbH..