Efficient merging of copper and photoredox catalysis for the asymmetric cross-dehydrogenative-coupling of alkynes and tetrahydroisoquinolines

Abstract

A highly efficient catalytic asymmetric alkynylation of prochiral CH2 groups in tetrahydroisoquinoline was developed using copper catalyzed cross-dehydrogenative-coupling of sp3 and sp C–H bonds with the assistance of a photocatalyst and visible light.

Enantioselective Catalysis of Photochemical Reactions

“…The oxidative photochemical preparation of 3,4-dihydroisoquinolinium ions has recently been successfully combined with the enantioselective copper-catalyzed addition of alkynes by the group of Li. [109] Among the copper ligands tested (including bisoxazolines [110] and diphosphanes), 1-(2diphenylphosphino-1-naphthyl)isoquinoline (QUINAP) was the most successful. Various 1-alkynylated N-arylated 1,2,3,4tetrahydroisoquinolines resulted from this reaction with high selectivity (60-97 % ee).…”

Metal-supported and -assisted stereoselective cooperative photoredox catalysis

“…In this copper cycle CuBr and (R)-QUINAP form the active catalyst, binding the alkyne substrate 40 and forming the product 41 with the corresponding iminium ion (Scheme 16bottom). 73 A complementary study of the functionalization of N-aryltetrahydroisoquinoline 39 was accomplished by the same group in 2016 (Scheme 17). 74 The THIQ 39 was arylated via a stereoselective photoredox catalysis by also including [Ir( ppy) 2 (dtbbpy)]PF 6 as a photosensitizer and a combination of copper(I) bromide and the chiral PhPyBox ligand as catalysts.…”

Cross-dehydrogenative coupling reaction using copper oxide impregnated on magnetite in deep eutectic solvents

“…General procedure for the N-arylation of tetrahydroisoquinolines. 27 Copper(I) iodide (200 mg, 1.0 mmol) and potassium phosphate (4.25 g, 20.0 mmol) were placed into a 50 mL twoneck flask. The flask was evacuated and back filled with argon.…”