THE WILLIAMSON REACTION - A NEW AND EFFICIENT METHOD FOR THE ALTERNATE RESOLUTION OF 2,2'-BIS(BROMOMETHYL)-1,1'-BINAPHTHYL AND 1,1'-BINAPHTHALENE-2,2'-DIOL

Treatment of 2,2'-bis(bromomethyl)-1,1'-binaphthyl [(R,S)-2] with 1, 1 '-binaphthalene-2,2'-diol(+)(R)-1 and cesium or potassium carbonate in refluxing acetone, gave the diastereoisomeric dioxacyclophanes (-)-(R ,S)-3a and (+)-(RF)-3b, both obtained in high yield, and the cyclic te traether (+)-(R,R,R,S)-4 as isolated side product. Boron tribomide-pro moted ether cleavage of 3a and 3b gave optically pure (-)-(S)-2 and ()-(R)-2, respectively, and the recovered diol (+)-(R)-1. Alternatively , the same reaction sequence furnished the resolved diols (-)-(S)-1 an d (+)-(R)-1 from (R,S)-1 and (+)-(R)-2, as well as optically pure 2,2' -bis(chloromethyl)-1, 1'-binaphthyl (+)-(R)-5 from the racemic dibromi de (R,S)-2 by using boron trichloride for ether cleavage.