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