PREPARATION OF ENANTIOMERICALLY PURE 1,1'-BINAPHTHALENE-2,2'-DIOL AND 1,1'-BINAPHTHALENE-2,2'-DITHIOL

A practical preparation of enantiomerically pure 1,1'-binaphthalene-2,2'-diol (1) and 1,1'-binaphthalene-2,2'-dithiol (2) is reported. Enantiopure 2 is obtained from enantiopure 1 via Newman-Kwart rearrangement of the thiocarbamoyl derivative 5 under controlled reaction conditions. The enantiopure starting diol 1 was obtained by a simple and inexpensive method engaging condensation of thiophosphoryl chloride and (S)-(-)-alpha-methylbenzylamine in pyridine and reaction of the resulting phosphoramidate a with racemic binaphthol 1 to give quantitatively a 1:1 mixture of diastereoisomers 4 that were cleanly separated by a single recrystallization from a chloroform-ethanol mixture in very high yield. The procedures can be scaled up easily.