Palladium-catalyzed tandem reaction of yne-propargylic carbonates with boronic acids: a simple method for the synthesis of fused aromatic rings through allene-mediated electrocyclization

Chemistry : a European Journal
Feng WangZhaoguo Zhang

Abstract

The palladium-catalyzed tandem reactions of yne-propargylic carbonates with aryl boronic acids, 2-furyl boronic acid, and 2-thiopheneboronic acid, followed by 6pi-electrocyclization to give fused ring aromatic products such as naphthalene, benzofuran, and benzothiophene derivatives are realized. Screening of the reaction conditions revealed that the combination of [Pd(PPh3)4] in THF gave the best results in terms of reactivity and product yields in the reaction of yne-propargylic carbonates with phenylboronic acid. The reaction is sensitive toward steric hindrance when substituted phenylboronic acids are employed. However, when we take 2-furyl boronic acid as the organometallic reagent, most substrates perform very well to give benzofuran derivatives. In addition, 2-thiopheneboronic acid is also a very effective coupling reagent to give bezothiophenes in high yields. A mechanism is proposed that involves the formation of an allenylpalladium complex from Pd0 and propargylic carbonate, followed by insertion of an intramolecular triple bond and the Suzuki coupling reaction, and then electrocyclization.

Citations

Feb 5, 1976·Biochimica Et Biophysica Acta·T Vassileva GrancharovaT Krumov Nikolov
Jan 20, 1977·Biochimica Et Biophysica Acta·A D RankineA A Coia
Oct 1, 1974·Journal of Steroid Biochemistry·A M Hill, D Trachewsky
Apr 27, 2021·Organic & Biomolecular Chemistry·Anton A NechaevEliška Matoušová
Aug 28, 2010·Organic Letters·Mitsuhiro YoshimatsuEri Koketsu
Aug 16, 2012·The Journal of Organic Chemistry·William T Spencer, Alison J Frontier
Dec 21, 2017·The Journal of Organic Chemistry·Hyeon Jin MunEun Joo Kang
Aug 13, 2005·The Journal of Organic Chemistry·Xin-hua DuanYong-min Liang

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