Synthesis of new optically pure tetrabromobenzotriazole derivatives via lipase-catalyzed transesterification

An efficient and convenient approach to synthesis of new, enantiopure hydroxyalkyl derivatives of 4,5,6,7-tetrabromo-1H-benzotriazole (TBBt) has been developed. Prochiral ketones synthesized through alkylation of TBBt were reduced to racemic secondary alcohols, which were separated by kinetic resolution carried out by lipase-catalyzed transesterification. After optimization of solvent, lipase and acyl donor group, the highest enantioselectivity factor (E > 200) and optical purity of the products (>99%) was achieved with lipase Amano AK from Pseudomonas fluorescens in tert-butyl methyl ether.