Lithium borohydride → (8-(4-Chlorophenylsulfonyl)-9-ethyl-1,4-dioxa-8-azaspiro[4.5]decan-7-yl)methanol

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Reaction Steps

Ethyl 8-(4-chlorophenylsulfonyl)-9-ethyl-1,4-dioxa-8-azaspiro[4.5]decane-7-carboxylate (110; 2.47 g, 5.92 mmol) and lithium borohydride (4.7 ml, 2.0 M in THF, 9.48 mmol) were added to THF (15 ml). The mixture was stirred for 18 hours under nitrogen at rt which led to only a 25% conversion to the desired alcohol. Solid lithium borohydride was added in equivalent portions and the reaction monitored until the starting ester was consumed. The reaction mixture was concentrated under reduced pressure, and equal portions of EtOAc and Rochelle's salt were added. The aqueous layer was washed with several more portions of EtOAc, dried with Na2SO4, and concentrated to give 2.44 g of crude oil. The material was purified by column chromatography using EtOAc/hexanes gradients to yield 1.26 g (57%) of a mixture of cis/trans isomers.

Provenance & Evidence