An internally activated tin hydride with enhanced reducing ability
摘要:
Tin hydride 1 is activated for nucleophilic hydride transfer and also for radical chain reduction, depending on solvent. The nucleophilic hydride pathway is favored in methanol, and 1 can be used as a selective reducing agent for ketones. Simple ketones are not reduced in aprotic solvents, but beta-hydroxy ketones are activated internally by the hydroxyl group and can be reduced in THF with good control of stereochemistry, as in the conversion from 7 to 9 (30:1 9:8). A catalytic version of the nucleophilic hydride reductions in methanol has been developed using PhSiH3 as the stoichiometric hydride source. Radical chain dehalogenations can also be achieved with 1 at room temperature and without added radical initiators. Simple xanthates are not reduced efficiently in the absence of an initiator, but the reaction proceeds in the presence of AIBN.