Reaction of organozinc reagents with carbonyl compounds in the presence of trialkylsilyl triflate

Abstract

Trialkylsilyl triflate promoted conjugate addition reactions of organozinc reagents such as diethylzinc and Reformatsky reagents to $\alpha,\beta$-unsaturated carbonyl compounds has been studied. The reactions of diethylzinc and Reformatsky reagents derived from t-butyl 2-bromoacetate with cyclic $\alpha,\beta$-enones inthe presence of trimethylsilyl triflate (TMSOTf) afforded the 1,4-adducts in high yields, whereas their reactions with cyclic $\alpha,\beta$-enones furnished the mixture of 1,2-and 1,4-adducts. Also, Reformatsky reagent prepared from ethyl 2-bromoacetate reacted with cyclic $\alpha,\beta$-enones giving the 1,4-adduct in moderate yields. On the other hand, studies on TMSOTf promoted addition of diethylzinc to aldehydes and ketones have been investigated. The reaction of diethylzinc to nonenolizable carbonyl compounds, i.e., benzaldehyde in the presence of TMSOTf furnished the addition product in excellent yield without the recovery of the starting material.