Solvent controlled divergent syntheses of polysubstituted pyrroles and pyrrolo[2,3-b]-1,4-thiazines
摘要:
The reaction of 2-imidazolyl carbene-derived 2-arylthiocarbamoyl imidazolium salts with ethyl propiolate proceeded via the solvent dependent tandem [3+2] cycloaddition and subsequent ring transformation processes. While the reaction in butanone yielded 3-amino-2-vinylthiopyrroles as the major products, use of benzene as the solvent led to the predominant formation of pyrrolo[2,3-b][1,4]thiazines. This work disclosed a unique ring transformation of imidazoline-spiro-pyrrolines to pyrFOIO[2,3b][1,4]-thiazines, which provides a simple route to both multifunctional pyrroles and pyrrolo[2,3b][1,4]thiazines that are other-wise difficult to synthesize. (c) 2008 Elsevier Ltd. All rights reserved.