Water mediated NHC-Pd (II) catalyzed oxidative coupling of benzoic acid and vinylarenes; Selective synthesis of five/six member isocoumarins

Abstract

Herein, a selective synthesis of isocoumarin and 3-benzylidenephthalides via Heck-type ortho-olefination of benzoic acids with vinyl arenes is reported under the mild reaction protocols. The present reaction was catalyzed by a well-established selenated NHC-Pd(II) pincer complex and Ag(OAc) as an oxidant. All reactions work in water, which is a green eco-friendly solvent; moreover, the method's effectiveness is highlighted by the selective synthesis of isocoumarin or 3-benzylidenephthalides in moderate to good yield. The functional group associated with benzoic acids and vinyl arenes did not exhibit any detrimental effect and displayed the protocol's efficacy. In a nutshell, the present method of oxidative coupling of benzoic acid and vinylarenes entail a lower amount of catalyst and oxidant loading, works effectively with green solvent water, and produces the selective isocoumarin product in 12–14 h under aerobic conditions.