A Photoinduced Multicomponent Regioselective Synthesis of 1,4,5‐Trisubstituted‐1,2,3‐Triazoles: Transition Metal‐, Azide‐ and Oxidant‐Free Protocol

Abstract

A transition metal-and azide-free approach is explored to synthesize 1,4,5-trisubstituted-1,2,3triazoles under sunlight. The reaction proceeds via CÀ N and NÀ N bond formations. These regioselective 1,2,3triazoles are obtained from isatin Schiff bases, benzaldehydes and tosylhydrazine in the presence of base. This protocol offers the structurally diverse 1,2,3-triazole derivatives with 75-90% yields.

Emerging trends in the sustainable synthesis of N–N bond bearing organic scaffolds

“…Finally, by the decarboxylation/dehydrogenation of intermediate I , the desired 1,2,3-triazole product is delivered (Scheme 15). 47…”

Transition‐Metal‐Free Synthesis of N‐Heterocyclic Compounds via Multi‐Component Reactions

“…A regioselective synthesis of 1,4,5-trisubstituted-1,2,3-triazoles 426 was reported by Basavoju and group using isatins Schiff bases 425, benzaldehydes 1 and tosylhydrazinein presence of sunlight and Cs 2 CO 3 as base (Scheme 80). [98] This photoinduced reaction occurred via formation of N-tosylhydrazone intermediate 427 generated insitu from aldehyde Gao and co-workers reported the regioselective synthesis of 1,4,5-trisubstituted 1,2,3-triazoles 443-445 via one-pot threecomponent coupling reaction (Scheme 82). [100] The reaction was ).…”

“…A regioselective synthesis of 1,4,5‐trisubstituted‐1,2,3‐triazoles 426 was reported by Basavoju and group using isatins Schiff bases 425 , benzaldehydes 1 and tosylhydrazinein presence of sunlight and Cs 2 CO 3 as base (Scheme 80). [98] This photoinduced reaction occurred via formation of N ‐tosylhydrazone intermediate 427 generated insitu from aldehyde 1 and tosylhydrazine, which gets converted into diazo intermediate 428 in the presence of Cs 2 CO 3 . The excitation of this intermediate 428 in the presence of sunlight and atmospheric oxygen yields a radical intermediate 429 .…”

Transition Metal‐ and Oxidant‐Free Regioselective Synthesis of 3,4,5‐Trisubstituted Pyrazoles by Means of [3+2] Cycloaddition Reactions

“…Our previous reports with tosylhydrazine encouraged us to check the feasibility of reaction under sunlight. [36] For this, when we conducted the reaction under dark condition, 80 % of yield was obtained (Scheme 2d). This indicates that the reaction is light independent.…”

“…[33] Recently, Ma et al disclosed transition metal free synthesis of 1,3,5-trisubstituted pyrazoles (Scheme 1c). [34] As part of our previous research on heterocyclic chemistry and in diazo chemistry, [35,36] herein we have established a new approach for the regioselective synthesis of poly functionalized pyrazoles via [3 + 2] cycloaddition of thiazolidinedione chalcones with N-tosylhydrazones under transition metal-and oxidant-free conditions (Scheme 1d).…”