Metal‐Catalyzed C–H Functionalization Processes with “Click”‐Triazole Assistance

Abstract

The functionalization of otherwise unreactive C–H bonds holds great promise for reducing reliance on existing functional groups while improving energy efficiency and atom economy. One of the most powerful strategies exploits chelation assistance through reversible coordination with metal catalysts. This microreview summarizes the most recent advances in the use of 1,2,3‐triazoles as versatile directing groups in the field of C–H functionalization. The main feature is the modular and straightforward assembly of the required triazoles through “click” chemistry, and such procedures therefore constitute practical synthetic tools of utmost importance for the late‐stage diversification of “click compounds”, which are ubiquitous moieties in drug discovery and material science.

Pd-catalyzed site-selective C(sp2)–H radical acylation of phenylalanine containing peptides with aldehydes

“…Although benzoyl-, tosyl- or acetyl-protected substrates devoid of an additional nitrogen-chelating unit remained unreactive, a related carboxamide bearing a 1,2,3-triazole unit could be also employed as an efficient bidentate DG, albeit in comparatively lower yields (Scheme 2). 14,16…”

5-Iodo-1H-1,2,3-triazoles as Versatile Building Blocks

“…1,2,3-Triazoles represent an example of DGs that have been used in C-H arylation, alkenylation, alkynylation, alkylation, and C-heteroatom bond formation. 124 It is of special interest that 5-iodotriazoles are also known to be employed as a DG for C(sp 2 )-H oxygenation 125 and rhodiumcatalyzed C-H bond functionalization of arenes with diazo compounds. 126 In the former transformation, the C5 iodo group of the triazole DG played a crucial role (Scheme 32).…”

Cu(I)-Catalyzed Click Chemistry in Glycoscience and Their Diverse Applications

“…The click approach using thermodynamically tested CuAAC exhibits exclusive characteristics (e.g., better tolerance for many functional entities and pH fluctuations, facile and milder reaction settings, and compatibility with diverse solvents along with water). These preferred traits make CuAAC a powerful tool for designing, developing, and reshaping complex organic entities of biological relevance. − …”