Direct Alkylation of α-Substituted Aldehydes

摘要

On the basis of extensive reported studies, alkylation of aldehydes is not considered to be a generally useful synthetic transformation. Aldol condensations and Can-nizzaro—Tishchenko reactions1 typically reduce the yields of the desired alkylated aldehydes severely. Reactions of potassium enolates of aldehydes containing one α-H atom with reactive alkylating agents (benzyl and allyl bromide, methyl iodide), in which 75-95% yields of the desired C-alkylated products were obtained, form an instructive exception. However, lower yields and unfavorable C/O alkylation ratios reported for less reactive electrophiles (BuI, iPrI) limit the usefulness of this approach.