Palladium-Catalyzed Tunable C2–H Aroylation or Arylation of Azoles with Thioesters

Abstract

2-Aryl and 2-acyl azole structural motifs widely exist in natural products, pharmaceuticals, agrochemicals and functional materials. Among various synthetic methods of 2-aryl and 2-acyl azoles, transition-metal-catalyzed direct C–H bond functionalization of azoles is more atom and step economical. A range of catalysts and reagents have been developed for the synthesis. However, tunable C2–H arylation and acylation of azoles employing the same reagent are rare and challenging. Thioesters as cheap and stable compounds are versatile building blocks in organic synthesis. They have been known to be effective arylation and acylation reagents when reacting with various organometallic reagents such as organozinc reagents, organoboron reagents, organosilicon reagents, organotin reagents, organoindium reagents, and organomanganese reagents. However, they were rarely used in C–H arylation and acylation reaction. In this paper, we report tunable C2–H aroylation and arylation of azoles with thioesters for the first time. Pd₂dba₃/P(m-tolyl)₃-catalyzed reaction of azoles with S-ethyl arylcarbothioates in dioxane at 80 °C in the presence of CuCl and tBuONa results in 2-aroylazoles. Similar reaction between benzoxazole or benzothiazole and S-dodecyl arylcarbothioates at 110 °C employing dcype as ligand affords 2-arylbenzoxazoles or 2-arylbenzothiazole. The method does not require activated thioesters, has a wide scope of substrates, good compatibility of functional groups, and controllable selectivity of acylation and arylation. Thioesters are easily prepared from the corresponding carboxylic acids. So, this protocol provides an alternative way to di(hetero)aryl ketones and di(hetero)aryl compounds bearing azoles from aromatic carboxylic acids.

Keywords

Azole / C–H functionalization / Thioester / Acylation / Arylation / Palladium / Copper / Catalysis / Cross-coupling / Decarbonylation

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2025 SIOC, CAS, Shanghai, & WILEY-VCH GmbH