Synthesis of mono- and di-potassium salts and methoxy adducts of sulfur-bridged biphenols by selective deprotonation

Treatment of the sulfur-bridged biphenol [1,1'-S(2-HOC6H2But-3-Me-5)(2)] with potassium hydride in diethyl ether results in the selective deprotonation of one phenol group to yield [1,1'-S(2-KO)(2'-HO)(C6H2But-3-Me-5)(2)(Et2O)], whereas an excess of potassium hydride in thf is required to generate the dianion [1,1'-S(2-KOC6H2But-3-Me-5)(2)(thf)(2)]; the same selective deprotonation is observed for the binaphthol [1,1'-S(2-HOC10H4Bu2t-3,6)(2)], suggesting that intramolecular H-bonding stabilises the second, remaining hydroxyl group, allowing new, simple routes to tuneable, mono- or di-anionic aryloxide-based ligands.