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Short Paper | Special issue | Vol 97, No. 2, 2018, pp.1288-1303
Published online, 20th June, 2018
DOI: 10.3987/COM-18-S(T)87
A Synthetic and Spectroscopic Investigation of the Asymmetric α-Lithiation-trapping of Six-Membered N-Boc Heterocycles Using Alexakis Diamines

James D. Firth, Giacomo Gelardi, Peter J. Rayner, Darren Stead, and Peter O'Brien*

*Department of Chemistry, University of York, Heslington, York YO10 5DD, U.K.

Abstract

The asymmetric lithiation-trapping of six-membered N-Boc heterocycles using s-BuLi and two different Alexakis diamines is reported. These readily available ligands outperform the current ‘best-in-class’ sparteine-type diamines in the lithiation and benzophenone trapping of N-Boc piperazines and the lithiation-cyclisation-trapping of N-Boc-4-chloropiperidine. In situ IR spectroscopy has been used to optimise lithiation times and to discover previously unknown subtleties regarding the lithiation step.