C-C COUPLING REACTION OF 1,5-DIBROMO-2,6-DIHYDROXYNAPHTHALENE WITH ALKALI 2-NAPHTHOXIDE - OPPOSITE EFFECTS OF COUNTERION COORDINATION AND HYDROGEN-BONDING ON STEREOSELECTIVITY IN THE FORMATION OF CIS-1,1' 5',1''-TERNAPHTHYL AND TRANS-1,1'/5',1''-TERNAPHTHYL/

The title reaction yields cis- and trans-2,2',6',2''-tetrahydroxy- 1,1 ':5',1''-ternaphthyls as the main products. In contrast to non-selecti ve distribution of the stereoisomers in the thermodynamic equilibrium, very high selectivity can be attained under conditions of kinetic con trol. The observed values of cis-/trans- ratios range between the extr emes 94:6 and 6:94, depending on the solvent and counterion employed. The coordination of the metal counterion plays a key role in the react ion performed in toluene, supporting formation of the cis-stereoisomer . When the coordination ability of the counterion is supressed by 18-c rown-6, intramolecular hydrogen bonding of the departing bromide group prevails in the stereocontrol, providing support for the trans-stereo isomer formation. Copyright (C) 1996 Elsevier Science Ltd