Highly asymmetric reduction of new benzofuryl and benzothiophenyl α-amino ketones

Heterocyclic compounds play an important role in the 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 of the 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 ketones (containing various azole rings) derivatives of benzofuran and benzothiophene were synthesized and subjected to the transfer hydrogenation with formic acid, catalyzed by RhCl[(R,R)-TsDPEN](C₅Me₅). The corresponding optically active β-amino alcohols were obtained in high yields and excellent enantioselectivities (93-99%), as determined by chiral HPLC. The absolute configuration of the products was confirmed by means of ECD spectroscopy supported by theoretical calculations.