Intramolecular ‘ene’ reactions of transient, allylic, and homoallylic C-nitrosoformate esters

Abstract

Various allylic and homoallylic alcohols have been treated successively with phosgene and hydroxylamine to form the corresponding N-hydroxycarbamic esters (3). Oxidation of these hydroxamic acid derivatives with sodium or tetraethylammonium periodate in the presence of cyclopentadiene gave the cycloadducts (5) derived from transient allylic and homoallylic C-nitrosoformate esters (4) and cyclopentadiene. When the cycloadducts were heated in benzene at 80 °C, or toluene at 111 °C, they dissociated and the C-nitrosoformate esters underwent intramolecular ‘ene’ reactions to give hydroxamic acid derivatives having newly formed, five- six- or seven-membered heterocyclic rings.