Enolate formation from cyclopropyl ketones via iodide-induced ring opening and its use for stereoselective aldol reaction

Abstract

Treatment of cyclopropyl ketones with TiCl 4- n-Bu 4NI mixed reagent provides ( Z)-titanium enolates which afford syn-α-iodethyl-β-hydroxyketones stereoselectively upon subsequent reaction with various aldehydes. The aldol adducts are cyclized into trans-acyltetrahydrofurans in good yield by active alumina. In contrast, the use of Et 2AlI in place of TiCl 4- n-Bu 4NI provides the corresponding anti aldol adducts with high stereoselectivity. These methods can complementarily provide both syn and anti isomers of α-iodoethyl-β-hydroxyketones from cyclopropyl ketones and aldehydes.