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  • Title: Efficient, regioselective access to bicyclic imidazo[1,2-x]- heterocycles via gold- and base-promoted cyclization of 1-alkynylimidazoles.
    Author: Laroche C, Kerwin SM.
    Journal: J Org Chem; 2009 Dec 04; 74(23):9229-32. PubMed ID: 19950886.
    Abstract:
    Reactions of 1-alkynylimidazoles involving the formation of their 2-lithio derivatives followed by addition of aldehydes or ketones are presented. The method gives access to 1-alkynyl-2-(hydroxymethyl)imidazoles which undergo 6-endo-dig or 5-exo-dig cyclization under AuCl(3)- or base-catalyzed conditions to yield imidazo[1,2-c]oxazoles and imidazo[2,1-c][1,4]oxazine heterocycles. Under transition metal catalysis, the reaction occurs in a regiospecific manner, leading exclusively to the product of 6-endo-dig attack, whereas under basic conditions, the reaction takes place in a regioselective manner giving preferentially the product from 5-exo-dig attack.
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