General and Efficient Copper-Catalyzed Oxazaborolidine Complex in Transfer Hydrogenation of Isoquinolines under Mild Conditions

Abstract

A general and efficient method for copper-catalyzed transfer hydrogenation of isoquinolines with an oxazaborolidine–BH 3 complex, under mild reaction conditions, is successfully developed. A broad range of isoquinolines has been reduced to the corresponding products with 61–85% yields. The method is applied to the synthesis of biologically active tetrahydrosioquinoline alkaloid (±)-norlaudanosine in 62% yield, which is the key precursor for the preparation of (±)-laudanosine, (±)- N -methyl-laudanosine, and (±)-xylopinine in one or two steps.

Chiral 8-Amino-5,6,7,8-tetrahydroquinoline Derivatives in Metal Catalysts for the Asymmetric Transfer Hydrogenation of 1-Aryl Substituted-3,4-dihydroisoquinolines as Alkaloids Precursors

“…The key synthetic step was the dynamic kinetic resolution of the starting material, the 5,6,7,8-tetrahydroquinolin-8-ol, carried out by lipase from Candida antarctica , overcoming the drawbacks occurring during the traditional resolution based on expensive chiral resolving agents often affording products in low yields and inadequate optical purity [ 31 ]. We deeply investigated the catalytic ability of the Cp* metal complexes of L1 and L2 in the asymmetric transfer hydrogenation (ATH) of a series of synthesized cyclic aromatic 1-aryl imines under mild aqueous reaction conditions [ 32 ]. Chiral L1 and L2 ligands featuring the pyridine backbone have already been demonstrated to perform extremely well in metal complexes when applied to homogeneous catalysis reactions, resulting in compatibility to both organic and aqueous media.…”