Distannoxane catalysts effect acylation of alcohols by action of esters and acetic anhydride. In particular, use of enol esters provides an extremely useful method. Primary alcohols are acylated in preference to secondary ones as well as phenol. Both acid- and base-sensitive functional groups remain intact. Especially unique is the discrimination of thio function which is completely tolerant under
Selective acylation of a sterically hindered hydroxyl group of unsymmetrical diols containing a primary hydroxyl group such as 1,5-hexanediol in the presence of silica gel with acetyl chloride
Highly Selective Acylation of Alcohols Using Enol Esters Catalyzed by Iminophosphoranes
作者:Palanichamy Ilankumaran、John G. Verkade
DOI:10.1021/jo990928d
日期:1999.12.1
The iminophosphorane bases PhCH2N=P(MeNCH2CR2)(3)N and PhCH2N=P(NMe2)(3) catalyze the acylation of primary alcohols with enol esters in excellent yields and in high selectivity. It was found that acid labile groups such as acetal and epoxide survive under the reaction conditions. Groups such as TBS and disulfide, which undergo cleavage in the presence of Ac2O and the Lewis acid Sc(OTf)(3), are also unaffected. Diene, conjugated acetylene, oxazoline, nitro, and benzodioxane groups are also compatible with our catalyst/reagent system. Because secondary alcohols do not react under our conditions, our methodology is attractive for the selective acylation of primary alcohols. Polymer-supported iminophosphorane catalysts are also shown to be useful in these reactions, thus opening the possibility of wider applications.
Distannoxane-Catalyzed Highly Selective Acylation of Alcohols