Stannylcarbamate 1 proved to be a selective agent for generating organotin(IV) enolates from alpha-halo ketones. Thus, a Darzens reaction was achieved under mild and neutral conditions. The reaction took place without any side reactions and even with aliphatic alpha-halo ketones bearing enolizable alpha'-hydrogens. Various types of alpha,beta-epoxy ketones and esters were obtained in this one-pot reaction. The stereoselectivity of the reaction was influenced by changing the halogen substituent of the alpha-halo ketones and by additives. Moreover, the present method could be applied to gamma- and delta-halo ketones as enolate precursors, and five- and six-membered cyclic compounds were obtained.
Simple Synthesis of Tetrahydrofurans via Reaction of Enolates of γ-Chloroketones with Aldehydes
作者:Mieczysaw Mąkosza、Micha Barbasiewicz
DOI:10.1055/s-2006-926387
日期:——
Enolates of γ-chloropropyl ketones react with aldehydes in protic media to form aldol type adducts that cyclize to substituted tetrahydrofurans, whereas in aprotic media they react mainly along an intramolecular substitution pathway giving cyclopropyl ketones. A substantial increase in the nucleophilicity of the enolates and the electrophilicity of aldehydes favors the formation of tetrahydrofurans.