Effect of Substituents and Stability of Transient Aluminum-Aminals in the Presence of Nucleophiles.

Disubstituted hydroxylamines were synthesized and used to form aluminum-amide complexes. These reagents masked carbonyl groups in situ from nucleophilic addition. The stability and utility of the aluminum-aminals are presented in the context of selectively controlling nucleophilic addition on substrates with multiple carbonyl groups.

Control of transient aluminum-aminals for masking and unmasking reactive carbonyl groups.

A new reagent, the dimethylaluminum N,O-dimethylhydroxylamine complex, is effective at masking reactive carbonyl groups in situ from nucleophilic addition. This reagent allows chemoselective addition of reducing reagents, Grignard reagents, organolithiums, Wittig reagents, and enolates into substrates with multiple carbonyl groups. Moreover, the trapped carbonyl group, a stable aminal, can be unmasked in situ for additional synthetic manipulations.