Synthesis of 1-tert-butyl-4-chloropiperidine:: Generation of an N-tert-butyl group by the reaction of a dimethyliminium salt with methylmagnesium chloride

Two efficient routes to 1-tert-butyl-4-chloropiperidine are described. In the first route, the key thionyl chloride mediated chlorination reaction features the use of tetrabutylammonium chloride as an additive that effectively suppresses the formation of an elimination-derived side product. In the second route, a novel alternative synthesis of 1-tert-butyl-4-chloropiperidine was developed in which the tertiary butyl group on the nitrogen is efficiently generated through the addition of methylmagnesium chloride to a dimeth-yliminium salt in 71% overall yield.