The development of an approach toward sterically-hindered chiral 2'-aryl-1,1'-binaphthalenes functionalized at position 2

摘要

Several approaches were examined for the preparation of l,l'-binaphthalene derivatives bearing steri-cally demanding ortho-substituted aryl at position 2' which are suitable for further functionalization at position 2. Steric hindrance of ortho-substituted aryl groups was critical for the approach through BINOL monotriflate. Among variations of cross-coupling reactions of 2,2'-dihalo-l,l'-binaphthalenes, Negishi arylation of an enantiopure 2,2'-dibromide was found to be the method of choice for regioselective and stereoconservative preparation of the target 2'-monoarylated precursor. Functionalization of the latter at position 2 was demonstrated by bromine substitution via lithiation followed by the reaction with several electrophiles.