The synthesis of a new class of stable azomethineylides 3 is reported. Compounds 3, containing a diazadiene system and a 1,3-dipole as well, and 2π-systems at the 1,3-dipole moiety.
The title compound 3 rearranges under very mild conditions to form 4,4-dicyano-8,8-dimethyl-2,6-diphenyl-3,5-diazabicyclo[5.1.0]octa-2,5-diene 5 (in alcohols) or dicyano[4-aroyl-5,5-dimethyl-2-aryl-1-azacyclopenta-1,3-diene-1-ium-1-yl]methanide 6 (in acetic acid). Azomethine ylide 6 adds to 2π-systems to form (3 + 2)-cycloadducts.
Nonstereospecific 1,3-dipolar cycloadditions of azomethine ylides and enamines
作者:Thomas Böhm、Andreas Weber、Jürgen Sauer
DOI:10.1016/s0040-4020(99)00517-7
日期:1999.7
The combination of electron-poor azomethine ylides 3 (AMY-I) or 4 (AMY-II) with electron-rich enamines 5 results in nonstereospecific 1,3-dipolar cycloadditions, which are LUMOdipole-HOMOdipolarophile controlled reactions. This phenomenon can be explained only by a two-step mechanism via zwitterionic intermediates.
Stable bicyclic, monocyclic and aromatic azomethine ylides 1, 13 and 16 add angle-strained, electron-rich and electron-poor alkynes as well as alkenes and heterocumulenes to form 1:1-adducts in highly stereoselective 1,3-dipolar cycloadditions. Unsymmetrical dipalarophiles react in a regiospecific manner. (C) 2000 Elsevier Science Ltd. All rights reserved.
Dicyano(7,7-dimethyl-2,5-di-p-tolyl-3,4-diazabicyclo[4.1.0]hepta-2,4-dien-3-ium-3-yl)methanide and (4-Benzoyl-5,5-dimethyl-2-phenyl-1-azacyclopenta-1,3-dien-1-ium-1-yl)dicyanomethanide, Two Stable Azomethine Ylides
作者:J. Breu、K. J. Range、P. Riebel、A. Weber、J. Sauer
DOI:10.1107/s0108270196001084
日期:1996.8.15
The azomethine ylide moieties of dicyano(7,7-dimethyl-2,5-di-p-tolyl-3,4-diazabicyclo[4. 1.0]hepta-2,4-dien-3-ium-3-yl)methanide, C24H22N4, and (4-benzoyl-5,5-dimethyl-2-phenyl-1-azacyclopenta-1,3-dien-1-ium-1-yl)dicyanomethanide, C22H17N3O, show normal bond distances and angles in comparison with related structures reported previously. The dipolar N-C distances of 1.430(4) and 1.401(3)Angstrom are appreciably shortened compared with the C-N+ bond lengths [1.485(9)Angstrom] found in N-substituted pyridinium compounds, which is consistent with previous observations. Both title compounds pack in such a way that the ylide dipoles are arranged above each other but pointing in opposite directions.