Synthesis and Thermolysis of Heterocyclic 3-Aza-3-ene-1,5-diynes1
摘要:
[GRAPHICS]Simple, acyclic 3-aza-3-ene-1,5-diynes undergo an aza-Bergman rearrangement to a fleeting 2,5-didehydropyridine (2,5-ddp) intermediate that rapidly ring-opens to beta-alkynylacrylonitrile products. In an effort to access longer-lived 2,5-ddp intermediates, we have prepared heterocyclic 3-aza-3-ene-1,5-diynes. The thermolysis of one such heterocyclic aza-enedlyne does not afford products derived from trapping a 2,5-ddp intermediate but rather cyclopropanes that appear to arise from a carbene intermediate and a product that appears to be a trapping product from a 2,3-ddp intermediate.
Thermal cyclization of 1,2-dialkynylimidazoles to imidazo[1,2-a]pyridines
作者:Asha K. Nadipuram、Sean M. Kerwin
DOI:10.1016/j.tet.2005.11.084
日期:2006.4
Thermolysis of 1,2-dialkynylimidazoles in chlorinated solvents leads to 5-chloroimidazo[1,2-a]-pyridine products, which are also formed in DMF containing 1 equiv of HCI. Deuterium labeling of the starting dialkynylimidazoles indicates that reaction may proceed by multiple pathways, depending upon conditions and substituents. Dialkynylimidazoles can also give rise to 5-diethylamino-substituted imidazopyridines when the thermolysis is carried out in the presence of diethylamine. (c) 2006 Elsevier Ltd. All rights reserved.