Palladium‐Catalyzed Synthesis of Benzothiophenes via Cross‐Dehydrogenative Coupling of 4‐Arylthiocoumarins and Pyrones

Abstract

Benzothiophenes represent a pivotal class of sulfur heterocycles and their synthesis has attracted significant attention to generate bioactive scaffolds. Herein, we report a convergent, atom-and step-economic method for the synthesis benzothiophenes by cross-dehydrogenative coupling (CDC) of 4-arylthiocoumarins in good to excellent yields. We further demonstrate cross-dehydrogenative coupling of 4-arylthio-2-pyrones to afford alternative substitution of benzothiophenes. The presence of a labile ester carbonyl moiety provides functional handle for further functionalization by coumarin deconstruction. Most crucially, the manuscript demonstrates that the use of readily accessible templated synthesis has a significant potential for the rapid assembly of sulfur heterocycles by dehydrogenative coupling mechanism.

Ruthenium(II)-Catalyzed Ortho-C–H Alkylation of Naphthylamines with Diazo Compounds for Synthesis of 2,2-Disubstituted π-Extended 3-Oxindoles in Water

“…π-Extended polycyclic heteroarenes play a pivotal role as versatile and important scaffolds in numerous natural products, biologically active molecules, and organic functional materials . Among them, π-extended 3-oxindoles (3-indolinones) display favorable optoelectronic properties and have found numerous applications as dyes and pharmaceutical products .…”

2‐Pyrone – A Privileged Heterocycle and Widespread Motif in Nature

“…Based on mechanistic studies, the excellent regioselectivity towards cyclized products 367 was rationalized by initial CÀ H activation of the 2-pyrone skeleton at C-3. [150] Equally, double CÀ H activations of 4-aniline [151] or 4-thioaryl [152] substituted pyrones led to the formation of indole-or benzothiophene fused products, respectively.…”

Transition metal-catalyzed coupling of heterocyclic alkenesviaC–H functionalization: recent trends and applications

“…170 A similar strategy is applied to benzothiophene synthesis (Scheme 113). 171 ortho-/para-Functionalized thiocoumarin/pyrone react well, while, the reaction of meta-functionalized substrates is not examined.…”