DERACEMIZATION OF DIARYLMETHANES VIA LATERAL LITHIATION-PROTONATION SEQUENCES BY MEANS OF SPARTEINE

Deracemization of diarylmethane derivatives was investigated by latera l lithiation-protonation mediated by (-)sparteine. Treatment of racemi c 4-phenyltetrahydroisoquinoline 1 with s-butyllithium-(-)-sparteine f ollowed by protonation of the resulting anion afforded (R)-phenyltetra hydroisoquinoline 1 in up to 88% e.e. Following the same procedure, ra cemic 2-(1-phenylethyl)pyridine 2 was subjected to the lithiation-prot onation sequence. The stereochemical outcome of the sequence proved to be highly dependent on the proton sources giving either (S)- or (R)-2 -(1-phenylethyl)pyridine 2 with EtOH or t-BuOH respectively in up to 5 0% e.e. (C) 1998 Elsevier Science Ltd. All rights reserved.