Silicon-mediated annulation. Part 2. A synthesis of β-alkoxy cyclo-octanones via intramolecular directed aldol reactions

Abstract

β-Alkoxycyclo-octanones were formed in poor to moderate yield by a Lewis acid-catalysed intramolecular directed aldol reaction between an acetal and an enol silane. From 10 examples, the effect of chain substitution, Lewis acid, and acetal structure on the efficiency of the 8-exo_eendo_n cyclisations was examined. The beneficial effect of gem-dimethyl substitution is discussed.