Iminophosphorane synthesis, 1,2,4-triazole

Several interesting 1,2,4-triazole fused-ring systems have been reported. A facile synthesis of 3,5-dihydro-677-imidazo[l,2-fc]-l,2,4-triazol-6-ones 162 was obtained by an iminophosphorane-mediated annulation <06EJ04170>. 8-Trifluoromethyl-l,2,4-triazolo[4,3- >]pyridazines 163 has been prepared from 4-trifluoromethyl-4,5-dihydropyridazin-3-one... 

The iminophosphorane 177 available from methyl azido(phenylhydrazo-no)acetate by a Staudinger reaction represents an ideal starting material for the synthesis of l//-l,2,4-triazoles (180). Two synthetic routes are possible (Scheme 68). The first is the reaction of iminophosphoranes with halides via isolable A-acylphosphonium salts (178), and imidoyl chlorides (179), leading to triazoles. The other approach involves the less reactive anhy-... 

Iminophosphoranes are being increasingly used in synthesis. The (triphenylphosphinimido)hydrazone (94) has been reported to react with both cyclic (95) and acyclic acid anhydrides to give 5-substituted-lH-l,2,4-triazoles (96) in variable yield.5 9 Excellent yields of iminolactam... 

Scheme 15.8 Synthesis of 5-iodo-l,4-disubstituted triazoles catalyzed by the iminophosphorane-Cu(I) complex 6 in water.

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