New Efficient Synthesis of 1,2,4‐Triazolo[5,1‐b]quinazolin‐9(3H)‐ones via a Tandem Aza‐Wittig/Heterocumulene‐Mediated Annulation

Abstract

The carbodiimides 2, obtained from aza-Wittig reactions of iminophosphorane 1 with aromatic isocyanates, react with hydrazine to give, selectively, the 3-amino-2-arylaminoquinazolin-4(3H)-ones 4. Reaction of 4 with triphenylphosphane, hexachloroethane and triethylamine produces iminophosphoranes 5. A tandem aza-Wittig reaction of iminophosphorane 5 with isocyanate or acyl chloride generates the 1,2,4-triazolo[5,1-b]quinazolin-9(3H)-ones 7 or 9, respectively, in

Synthesis and anti‐HIV activity of n‐(3‐amino‐3,4‐dihydro‐4‐oxopyrimidin‐2‐yl)‐4‐chloro‐2‐mercapto‐5‐methylbenzenesulfonamide derivatives

“…It should be pointed out that 3-amino-2-arylsulfonamidoquinazolin-4(3H)-ones have not been described previously. However, it was found [20] that the amino-262 Z. Brzozowski and F. S czewski Vol 44 guanidine compounds of type A generated by the treatment of 2-phenyliminomethyleneamino-benzoic acid esters with hydrazine underwent a facile cyclocondensation at room temperature giving rise to the formation of corresponding 3-amino-2-phenylamino-3H-quinoxalin-4-ones.…”

Ring Closure Reactions in Heterocyclic Systems with Implementation of Wittig and aza-Wittig Reactions

“…A ring opening to (c) and, then, a repeated cyclization to a triazine-N-oxide (d) can follow. This second cyclic intermediate can again undergo a ring opening to (e) by an retro-electrocyclization step as shown by the Formation of fused aminotriazoles has been described by Ding et al [53] (Scheme 39). The precondition of the successful cyclization is the preparation of the carbodiimide 174 by an aza-Wittig reaction of the phosphazane bearing an arylamino group (173) and an aryl isocyanate.…”

Efficient synthesis of 2‐substituted thieno[2,3‐d]pyrimidin‐4(3H)‐ones via an iminophosphorane

“…Synthetically useful approaches to thienopyrimidinones starting from easily accessible 2-amino-3-carboxythiophenes are, therefore, of great importance. Recently, we have become interested in the preparation of N-heteroaryliminophosphoranes because these species are promising building blocks for the synthesis of nitrogen heterocycles [14][15][16][17][18]. Herein, we report an efficient synthesis of various 2-substituted 5-ethyl-6-methyl-thieno [2,3-d]pyrimidin-4(3H)-ones via iminophosphorane 3.…”