A quick and low E-factor waste valorization procedure for CuCl-catalyzed oxidative self-coupling of (hetero)arylboronic acid in pomegranate peel ash extract

Abstract

The application of waste biomass-derived materials to synthetic chemistry is a remarkable achievement, and the use of aqueous media is further advancement. The switch towards earth's abundant metals like cobalt/copper/iron/nickel from precious palladium in C–C coupling reactions is also a high throughput in the global sustainability perspective. Herein, we describe a CuCl-catalyzed homocoupling of (hetero)arylboronic acids (HABAs) in water extract of pomegranate ash (WEPA) with low E-factor of 1.25 without including the column chromatographic separation of products, which helped in understanding the effectiveness of this method on comparison to reported protocols lacking amounts of silica gel and eluents, however, it was 171.64 by including column purification. The reactions are conducted at room temperature to deliver self-coupling products with 90–99% yields in 10–45 min under precious metal, ligand, non-renewable base, toxic/problematic organic solvent and added oxidant-free conditions. A wide range of substrates were screened with aryl and heteroaryl moieties containing diversified functional groups. The substitution of earth's rare metals-based catalysts by abundant copper, exploration of waste to state-of-the-art C–C coupling, use of biorenewable base, aqueous media, ambient conditions, operational simplicity, excellent yields of biaryls and quick reactions are the noteworthy advantages of this protocol.

Keywords

• CuCl-WEPA
• waste volarization
• (hetero)arylboronic acids
• oxidative self-coupling
• symmetrical biaryls
• low E-factor