Synthesis and synthetic applications of 1-metallo-1-selenocyclopropanes and -cyclobutanes and related 1-metallo-1-silylcyclopropanes

Abstract

Among the α-heterosubstituted cyclopropylmetals α-selenocyclopropyllithiums represent some of the most valuable synthetic intermediates. They are quantitatively prepared from selenoacetals of cyclopropanones and butyllithiums, are thermally stable at ∼−78° for several hours and are particularly nucleophilic especially towards carbonyl compounds. The cyclopropyl derivatives containing a selenenyl moiety have been transformed to selenium free derivatives such as alkylidene cyclopropanes, vinyl cyclopropanes, allylidene cyclopropanes, cyclobutanones and α-silyl cyclopropyllithiums. The latter compounds have been used as starting material for the synthesis of alkylidene cyclopropanes and cyclopentenyl derivatives. α-Seleno cyclobutyllithiums, which are available in two steps from cyclobutanones, also permit the synthesis of various selenium free homologues such as alkylidene cyclobutanes, vinyl cyclobutanes, oxaspirohexanes and cyclopentanones.