General methodology for the chemoselective N-alkylation of (2,2,6,6)-tetramethylpiperidin-4-ol: Contribution of microwave irradiation

A convenient method to access a broad variety of N-alkyl-(2,2,6,6)-tetramethylpiperidin-4-ol compounds is reported. The thermal treatment of a mixture of (2,2,6,6)-tetramethylpiperidin-4-ol and allyl or benzyl bromide derivatives gave the corresponding N–alkylated compounds in good yields while leaving the hydroxyl functional group intact. Whereas 40?h were needed to reach complete conversion, microwave irradiation allowed the reaction time to be reduced (20?min) and improved the yields in most cases.