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-3Me-5)2(thf)2]; the same selective deprotonation is observed for the binaphthol [1,1-S(2-HOC10H4But2-3,6)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.