Reaction of 1,4-Dibromo-2,3-dihydroxynaphthalene with 2-Naphthoxide Ion. Solvent and Cation Control in the Formation of the Conformationally Locked Stereoisomers of 2,2‘,3‘,2‘‘-Tetrahydroxy-1,1‘:4‘,1‘‘-ternaphthyl and 2,2‘,3‘,2‘‘,3‘‘,2‘‘‘-Hexahydroxy-1,1‘:4‘,1‘‘:4‘‘,1‘‘‘-quaternaphthyl

Abstract

The reaction of the dibromide 1 with the 2-naphthoxide ion 2 proceeds under remarkably mild conditions (25−50 °C), yielding all possible stereoisomers of ternaphthol 3 and quaternaphthol 4. An unambiguous structure assignment has been made for the individual stereoisomers and conditions for their thermal interconversion have been established. In contrast to a nonselective distribution of stereoisomers found in the thermodynamic equilibrium mixture, a high stereoselectivity can be induced in the coupling reaction under kinetic control. The coordinating ability of the alkali metal counterion (M+) of the participating 2-naphthoxide ion 2 has been found to play a key role in the stereocontrol, supporting strongly the formation of the cis stereoisomers of 3 and 4. When the coordinating ability of M+ is suppressed by an efficient solvation and/or by complexation with 18-crown-6, formation of the trans stereoisomers prevails in the reaction.