BF3 complexes of typical benzylic, allylic and saturated N-methyl tertiary amines were a-lithiated, with lithium tetramethylpiperidide (LTMP) or sec-butyllithium, and were treated with electrophiles.This Communication describes the concept of facilitating a-deprotonation of heteroatom compounds by complexation with a Lewis acid, and shows its utility for regioselective formation of C-C bonds in some tertiary amines (Scheme 1). $ Tertiary amines offer a real test of this idea since nitrogen, unlike phosphorus and sulphur, does not provide sufficient t Part of this work was presented at the 17th IUPAC International
Metallation of BF3-pyridine complex with lithium tetramethylpiperidide (LTMP) in ether at -78 "C, followed by reaction with carbonyl compounds, affords a-pyridyl alcohols in good yields. a-Pyridyl alcohols, which are intermediates of some pharmacological interest ,132 are often synthesised from halogen derivatives or N-oxides of pyridine because direct metallation of this heterocycle is deemed impractical.3-5 It was, therefore, of interest to see if Lewis acid complexation can be used for this purpose (Scheme 1).6Our attempts to obtain the alcohol 3a through deprotonation of pyridine with the highly hindered base lithium tetramethylpiperidide (LTMP) furnished only 2,2'-bipyridy17 at -78"C, while no reaction was observed at -120°C. However, treatment of an ether solution? of the BF3-complex 1 with LTMP at -78 "C, followed by addition of benzaldehyde afforded 3a8 in 85% yields.$ The alcohol 3b9 (87%) was t Use of tetrahydrofuran (THF) as solvent gave inferior yields. Also reactions with methyl iodide and benzyl chloride proceeded poorly.
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