One-pot synthesis of thiazolo[3,4-a]quinoxalines and the related heterocyclic systems using 4-hydroxy-4-alkoxycarbonyl-3,5-diaryl-2-aryliminothia(selena)zolidines as versatile reagents

An efficient and versatile one-step method for the synthesis of thiazolo[3,4-a]quinoxalines and related new heterocyclic systems have been developed on the basis of a new strategy for the construction of the pyrazine ring system. The key step of the process involves the cascade annulation of the iminothiazolopyrazine system to benzene in the reaction of 4-hydroxy-3,5-diaryl-2-phenyliminothiazolidines with 1,2-diaminobenzenes. The use of selenium analogues instead of thiazolidine derivatives in this reaction, leads to selenazolo[3,4-a]quinoxalines and the use of aza analogues instead of 1,2-diaminobenzenes gives aza analogues of thiazolo[3,4-a]quinoxalines.