Dinuclear zinc catalysis of a kinetic resolution strategy for distinguishing one pair of diastereoisomers from multiple stereoisomers

Abstract

A new kinetic resolution strategy of distinguishing four stereoisomers is realized. The dinuclear zinc catalysts based on a multidentate semi-azacrown ether ligand and ZnEt₂ are identified as superior catalysts for this transformation. The highly enantioselective kinetic resolution of 1-tosylindoline-2,3-diols has been achieved via a reverse hemiacetal/tautomerization reaction. Remarkably, the enediol intermediates can be captured by unsaturated nitro compounds via a Michael addition reaction. In addition, the products could be transformed to indolin-3-one and benzoxazine spiro-pyran derivatives. A proposed mechanism was assumed to explain the observed KR results and enantioselectivity.