Catalyst and base controlled site-selective sp2 and sp3 direct arylation of azine N-oxides
摘要:
Site-selective direct arylation of both sp(2) and sp(3) sites on azine N-oxide substrates is described. The arylation reactions are carried out in either a divergent manner or a sequential manner The sp arylation reaction is applied to the synthesis of the natural products, papaverine and crykonisine, and. rationale for low reactivity of electron-deficient aryl halides is provided. Mechanistic investigations point toward the intimate involvement of the base in the mechanism of these reactions. (C) 2008 Published by Elsevier Ltd.