Unsaturated Nitriles: Precursors for a Domino Ozonolysis-Aldol Synthesis of Oxonitriles.

Cyclic five-, six-, and seven-membered oxonitriles are prepared by a tandem ozonolysis-aldol sequence. Cyclopentenylacetonitrile (4) and cyclohexenylacetonitrile (12) afford the ring-expanded oxonitriles 3 (98%) and 17 (58%), respectively, in highly efficient one-pot syntheses. Homologous five-membered oxonitriles 22a-c are prepared by analogous ozonolysis-aldol cyclizations employing omega-alkenyl beta-ketonitriles. The method tolerates various substitution patterns and allows for the synthesis of beta,beta-disubstituted oxonitriles (22c). The reaction conditions are essentially neutral providing the beta-hydroxyoxonitriles 22d and 22e with only trace amounts of the aromatic dehydration product.