Easy One-Pot Synthesis of 1-Monosubstituted Aliphatic 1,2,3-Triazoles from Aliphatic Halides, Sodium Azide and Propiolic Acid by a Click Cycloaddition/Decarboxylation Process

Decarboxylative click cycloaddition: an emerging strategy towards substituted 1,2,3-triazole derivatives

1,2,3-triazole is a vital structural motif of various drugs and therapeutic leads, as well as a linker for bioconjugation and molecular recognition. Cu-catalysed click cycloaddition of azides with terminal alkynes (CuAAc) is an important reaction to construct the triazole core. In recent years, various decarboxylative click strategies utilizing alkynoic acids as stable surrogates for low boiling or gaseous alkynes have been developed. For instance, propiolic acid, which is easy to transport, is a safe alternative for flammable gaseous acetylene. In this review article, we have covered the recent development in the decarboxylative click cycloaddition of alkynoic acids with azides leading to the synthesis of diversely substituted triazoles, including monosubstituted, 1,4-disubstituted and fully substituted 1,2,3-triazoles. Various aspects such as mechanistic insights and optimization conditions/role of catalyst are highlighted.

Copper-Promoted One-Pot Sandmeyer-Type Reaction for the Synthesis of N-Aryltriazoles

Herein, we report the copper-catalyzed one-pot Sandmeyer-type reaction of aromatic amines with triazoles to afford N-aryl-1,2,3-triazoles. Diazonium salts, formed from aromatic amines and tert-butyl nitrite in the presence of fluoroboric acid, reacted with triazoles in a copper-catalyzed Sandmeyer-type reaction. The reaction proceeded under mild conditions to afford N-aryltriazoles in moderate to good yields. This method is amenable to a wide range of aromatic amines and triazoles and shows diverse functional group tolerance. Inhibition of the reaction upon the addition of free radical scavengers suggested a radical pathway, in which the aryl radical, copper, and triazole formed a complex that underwent reductive elimination to give aryltriazole compounds; this is consistent with the mechanism underlying the Sandmeyer reaction. Thus, we demonstrate a new effective strategy for the construction of C-N bonds via Sandmeyer-type reactions and a valuable alternative approach for the synthesis of aryltriazole derivatives.

A Facile Total Synthesis of Mubritinib

A five-step, practical, and concise total synthesis of mubritinib is described. The synthesis utilized Friedel–Crafts acylation, click reaction, reduction, and demethylation for the construction of the triazole ring system as key steps. Another important feature of this synthesis is the Bredereck oxazole synthesis. The main advantages of this process are the improved yield and decreased number of reaction steps, which paves the way for the industrial-scale synthesis of mubritinib.

Controlled photorelease of alkynoic acids and their decarboxylative deprotection for copper-catalyzed azide/alkyne cycloaddition

A controlled photorelease of alkynoic acids from a photoremovable protecting group (PPG) facilitates their subsequent decarboxylation to deliver terminal alkynes for a Cu^I-catalyzed azide/alkyne cycloaddition.