α-Alkylation of Aldehydes by S_N1-Type Reaction of Alcohols

Significance

Alcohols capable of forming stabilized carbocations were used as the alkylating reagents for aldehydes. A catalytic amount of secondary amine salt 1 in Et₂O gave α-alkylated aldehydes 2 in moderate to good yields and good enantioselectivity with H₂O being the only byproduct. In this simple procedure the ammonium salt acts as an aminocatalyst but also as an acid to generate the carbocation from the alcohol.