Two reaction modes of 1-sulfonyl-1,2,3-triazoles and pyridinium 1,4-zwitterionic thiolates: catalyst-free synthesis of pyrido[1,2-a]pyrazine derivatives and 1,4-thiazine derivatives

Abstract

Two reaction modes of 1-sulfonyl-1,2,3-triazoles and pyridinium 1,4-zwitterionic thiolates were described. Pyrido[1,2-a]pyrazine derivatives were obtained in moderate yields when 4-OEt substituted triazoles were employed in reactions, and 1,4-thiazine derivatives were...

Recent advances in the cyclization reactions of pyridinium 1,n-zwitterions (n = 4 and 5): scope and mechanism

“…In 2021, Li et al described the synthesis of nitrogen-containing heterocyclic derivatives 33 via the reaction of pyridinium 1,4-zwitterionic thiolates 1 and 1-sulfonyl-1,2,3-triazoles ( 32 and 34 ) (Scheme 7). 29 When 4-OR 1 -substituted triazoles 32 were treated with pyridinium 1,4-zwitterionic thiolates 1 in 1,2-dimethoxyethane (DME) at 80 °C, pyrido[1,2- a ]pyrazine derivatives 33 were obtained in moderate to good yields. However, when the 4-OR 1 substituted triazoles 32 were replaced with 4-NPhth-substituted triazoles 34 in refluxing CHCl 3 , 1,4-thiazine derivatives 35 were obtained instead of 33 from the reaction.…”

Recent Progress in Heterocycle Synthesis: Cyclization Reaction with Pyridinium and Quinolinium 1,4-Zwitterions

“…Formal (3 + 3) cyclization reactions belong to a class of important and powerful reactions that help synthesize six-membered heterocyclic rings. Li et al devised a catalyst-free (3 + 3) cyclization strategy using pyridinium 1,4-zwitterions 1 to synthesize 1,4-thiazine derivatives 35 ( Scheme 10 ) [ 57 ]. The reactions with 4-NPhth substituted triazoles 34 were carried out in CHCl 3 under conditions of reflux, and moderate-to-good yields were observed.…”

“…In 2021, Li et al achieved a (4 + 2) cyclization between 1-sulfonyl-1,2,3-triazoles 87 and pyridinium 1,4-zwitterions 1 through an addition/elimination process, accessing pyrido[1,2- a ]pyrazine derivatives 88 . The products were formed in yields of up to 70% ( Scheme 19 ) [ 57 ]. The authors proposed a mechanism to explain the observed results.…”

Domino assembly of dithiocarbamatesviaCu-catalyzed denitrogenative thiolation of iodotriazole-based diazo precursors

“…Moreover, to the best of our knowledge, the employment of N -sulfonyltriazoles in C–S bond forming cascades may be possible only by the use of very expensive Rh catalysts. 30,31 It is worth mentioning that the structural analogues of the obtained products, containing benzimidazole and benzothiazole units, have been shown to exhibit fungicidal, 32 antiviral, 33 and anticancer 34 activities (Scheme 1D).…”