Highly Asymmetric Reduction of New Benzofuryl and Benzothiophenyl α-Amino Ketones ^†

Heterocyclic compounds play an important role in medicinal chemistry and occupy a central position in synthetic organic chemistry. Both benzofuran and benzothiophene are considered as very important structures due to their diverse biological and pharmacological profile. Many clinically approved drugs are synthetic and naturally occurring substituted benzofuryl and benzothiophenyl derivatives in conjunction with other heterocycles. Therefore, a new series of α-amino ketone (containing various azole rings) derivatives of benzofuran and benzothiophene are synthesized and subjected to the transfer hydrogenation with formic acid, catalyzed by RhCl[(R,R)-TsDPEN](C₅Me₅). The corresponding optically active β-amino alcohols are obtained in high yields and excellent enantioselectivities (93%–99%), as determined by chiral HPLC (high-performance liquid chromatography). The absolute configuration of the products is confirmed by means of ECD (electronic circular dichroism) spectroscopy, supported by theoretical calculations.