Alkylation of aldehyde arenesulfonylhydrazones via trialkylboranes

A new methodology for delivering alkyl groups to carbonyl moieties via trialkylboranes was developed. This new reaction is a useful alternative to the traditional alkylmetal reactions.

Arenesulfonylhydrazone derivatives of aryl aldehydes are easily alkylated by trialkylboranes in the presence of base to give the corresponding substituted alcohols after oxidation. Both tosyl and trisyl derivatives may be utilized in this new reaction. The reaction tolerates several different functional groups thereby allowing functionalized alkyl groups to be transferred. The applicability of various blocked borane derivatives was also evaluated.

The methodology can be extended to alkyl aldehydes via the trisyl derivatives. The usefulness of blocked borane derivatives was evaluated.

Several approaches to the direct 1,2-addition of a trialkylborane to a carbonyl group were attempted. Future approaches to this problem were also discussed.