Asymmetric lithiation trapping of N-Boc heterocycles at temperatures above -78 °C.

Org Lett

Department of Chemistry, University of York, Heslington, York YO10 5DD, U. K., and Neusentis Chemistry, Pfizer Worldwide Research and Development , The Portway Building, Granta Park, Cambridge CB21 6GS, U. K.

Published: November 2013

The asymmetric lithiation trapping of N-Boc heterocycles using s-BuLi/chiral diamines at temperatures up to -20 °C is reported. Depending on the N-Boc heterocycle, lithiation is accomplished using s-BuLi and (-)-sparteine or the (+)-sparteine surrogate in the temperature range -50 to -20 °C for short reaction times (2-20 min). Subsequent electrophilic trapping or transmetalation-Negishi coupling delivered functionalized N-Boc heterocycles in 47-95% yield and 77:23-93:7 er. With N-Boc pyrrolidine, trapped products can be generated in ∼90:10 er even at -20 °C.

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Source
http://dx.doi.org/10.1021/ol402395jDOI Listing

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