Catalytic Sc( OTf ) 3 mediated direct asymmetric aldol reaction of (−)‐menthyl isothiocyanatoacetate with aldehydes by using (−)‐menthol as chiral auxiliary

This method involves the direct asymmetric aldol reaction of (−)‐menthyl isothiocyanatoacetate 5 with a variety of substituted aromatic aldehydes, which offers a convenient method for the synthesis of intermediate containing biologically relevant α‐amino β‐hydroxyl groups in oxazolidine ring. In this methodology, the products show remarkable diastereoselectivity using Sc(OTf) 3 as a catalyst and easily accessible (−)‐menthol as a chiral auxiliary. This approach includes some important aspects such as mild reaction conditions, high yields, and excellent diastereoselectivity with a number of substituted aromatic aldehydes. The optimization and effect of different catalysts were studied at different reaction conditions and it is found that Sc(OTf) 3 shows excellent diastereoselectivity at −45°C.