Synthesis of Indeno[1,2-c]furans via Cobalt-Catalyzed Radical–Polar Crossover [3 + 2] Cycloaddition of o-Alkynylaryl β-Dicarbonyls

Abstract

Fused polycyclic furans are privileged structural scaffolds in materials chemistry, including organic semiconductors. Specifically, indeno[1,2-c]furans are an interesting type of polycyclic furans featuring a fused furan and indenone framework. Unfortunately, limited studies on their photophysical properties have been performed, probably owing to the lack of efficient and straightforward approaches to those compounds. Herein, we have developed a cobalt-catalyzed radical−polar crossover cyclization of the readily available o-alkynylaryl β-carbonyls to afford diverse indeno[1,2-c]furans. Photophysical and DFT calculations were also carried out, suggesting that the obtained indeno[1,2-c]furans exhibit promising electronic and optical properties.

Batch and Continuous-Flow Electrochemical Geminal Difluorination of Indeno[1,2-c]furans

“…Regarding the starting materials, we previously demonstrated that indeno[1,2-c]furans (1) can be readily prepared from o-alkynylaryl-tethered β-dicarbonyls via a cobalt-catalyzed radical−polar crossover strategy with superstoichiometric Nfluorobenzenesulfonimide (NFSI) as the oxidant. 46 Starting from o-alkynylaryl-tethered β-dicarbonyl (4a), constantcurrent electrolysis (I = 3 mA) in the presence of Et 3 N•3HF also generated the target indeno[1,2-c]furan (1a) in 65% yield (Scheme 4 and Scheme S6). Compared with the chemical approach, this electrochemical reaction features a simple operation and is greener and more sustainable, as it obviates the need for transition metals as well as excess oxidants of economic and environmental concern.…”

“…Regarding the starting materials, we previously demonstrated that indeno­[1,2- c ]­furans ( 1 ) can be readily prepared from o -alkynylaryl-tethered β-dicarbonyls via a cobalt-catalyzed radical–polar crossover strategy with superstoichiometric N -fluorobenzenesulfonimide (NFSI) as the oxidant . Starting from o -alkynylaryl-tethered β-dicarbonyl ( 4a ), constant-current electrolysis ( I = 3 mA) in the presence of Et 3 N·3HF also generated the target indeno­[1,2- c ]­furan ( 1a ) in 65% yield (Scheme and Scheme S6).…”