Selective benzylic lithiation of N-Boc-2-phenylpiperidine and pyrrolidine: expedient synthesis of a 2,2-disubstituted piperidine NK1 antagonist

Boc-phenyl piperidine and Boc-phenyl pyrrolidine are selectively lithiated at the 2-position and trapped with a variety of electrophiles. The chemistry is used to make a sub-nanomolar inhibitor of the human neurokinin 1 receptor.