Preparation of a spiroisoxazolinopiperidinylbenzamide-based scaffold

A route to spiroisoxazolinopiperidinylbenzamides has been developed. N-Boc-4-piperidone underwent a Wittig olefination and Boc-deprotection followed by a nucleophilic substitution reaction with 4-fluoro-3-nitrobenzoic acid to yield the starting scaffold 3 in excellent yields. Diversification of the acid with primary amines, followed nitrile oxide formation in situ (aryl oximes treated with bleach) and subsequent 1,3-dipolar cycloaddition to the exo-methylene moiety delivered the spiroisoxazolinopiperdines. Reduction of the arylnitro group followed by acylation with acid chlorides or reductive amination with aldehydes yielded the spiroisoxazolinopiperidinylbenzamide library.