Enantioselective Synthesis of Arylglycine Derivatives by Asymmetric Addition of Arylboronic Acids to Imines

Abstract

Rhodium-catalyzed enantioselective 1,2-additions of arylboronic acids to N-tosyl furanylimine and lithium 5-methyl-2-furanyltriolborate to N-tosyl arylimines giving aryl(2-furanyl)methanamines were developed for enantioselective synthesis of arylglycines by ozonolysis of the furyl ring. A chiral N-linked C2-symmetric bidentate phosphoramidite (N-Me-BIPAM) achieved high enantioselectivities up to 99 % ee. For the direct synthesis of arylglycines, the asymmetric addition of arylboronic acids to ethyl N-p-methoxyphenyl iminoester was carried out at 80°C in dioxane in the presence of Rh(acac)(C2H4)2/(R,R)-N-Me-BIPAM. The reaction gave optically active arylglycines in up to 99 % ee.