Synthesis of 2‐Azaindolizines by Using an Iodine‐Mediated Oxidative Desulfurization Promoted Cyclization of N‐2‐Pyridylmethyl Thioamides and an Investigation of Their Photophysical Properties.

Abstract

Properties. -Various functionalized 2-azaindolizines are prepared from readily available thioamides. The reaction strongly depends on the time and the solvent allowing the preparation of sulfur-bridged dimers [cf. (III)] as well. Product (IIe) is transformed to fluorescent derivatives using transition metal-catalyzed cross-couplings. -(SHIBAHARA*, F.; KITAGAWA, A.; YAMAGUCHI, E.; MURAI, T.; Org. Lett. 8 (2006) 24, 5621-5624; Dep. Chem., Fac. Eng., Gifu Univ., Yanagido, Gifu 501-11, Japan; Eng.) -R. Steudel 14-159

CBr4 Mediated [4 + 1] Dehydrocyclization for the Synthesis of Functionalized Imidazo[1,5-a]heterocycles from Pyridin-2-ylmethanamines and Aldehydes

“…1,2 Many efforts were devoted by chemists to the synthetic method development, and several reaction systems were successfully applied in the synthesis of imidazo[1, 5a]heterocycles, in which a typical [3 + 2] strategy was mostly employed. These reports could be roughly summarized as three categories that are different from the classical Vilsmeiertype cyclization, 3 I 2 promoted oxidative cyclizations, 4,5 coppercatalyzed and promoted oxidative cyclization, 6−11 and electrochemistry methods. 12,13 These methods well enriched the synthetic approaches for imidazo[1,5-a]heterocycles; however, relatively violent reaction conditions, such as high temperatures, heavy metals (copper salts), and limited functional group tolerance, hampered their application prospect.…”