1,3-Diaza-2-azoniaallene Salts as Novel N3-Building Blocks: Preparation and cycloadditions to alkenes, alkynes, carbodiimides, and cyanamides
作者:Wolfgang Wirschun
DOI:10.1002/prac.19983400403
日期:——
1,3-Diaza-2-azoniaallene salts R-1-N=N+=N-R-2 6 represent a new functional group. 1,3-Disubstituted triazenes 8 are oxidized with tert-butyl hypochlorite to stable open-chain N-chlorotriazenes R-1-N=N-NCl-R-2 9, which at low temperatures with Lewis acids afford the reactive intermediates 6. The salt 6a is stable below -50 degrees C and was characterized by spectroscopic and analytical data. Heterocumulenes 6 behave as positively charged 1,3-dipoles undergoing cycloadditions to many different multiple bonds to furnish 1,2,3-triazolium and tetrazolium salts, e.g. to both electron-rich and electron-deficient alkenes, alkynes, to one or both double bonds of 1,3-butadienes, to carbodiimides, and cyanamides (1,3-dipolar cycloaddition with inverse electron demand). With an allene, a butatriene and a pentatetraene the 4,5-dihydro-1H-1,2,3-triazolium salts 17-19 were obtained. The constitutions of four of the products were secured by X-ray structural analyses. 4,5-Dihydro-1H-1,2,3-triazolium salts 11 and 1H-1,2,3-triazolium salts 20 are aza analogues of Arduengo's and Wanzlick's nucleophilic carbenes.