WEPA: a bio-derived medium for added base, π-acid and ligand free Ullmann coupling of aryl halides using Pd(OAc)₂

Abstract

Water extract of pomegranate ash (WEPA), an agro waste (bio) derived novel and sustainable medium, has been developed for the Ullmann coupling of aryl halides under added base, ligand and reducing agent free palladium catalysis in open-air.

Palladium‐catalysed room‐temperature Suzuki–Miyaura coupling in water extract of pomegranate ash, a bio‐derived sustainable and renewable medium

“…WEPA was prepared from pomegranate skins according to our recent report on WEPA‐mediated Ullman coupling of aryl halides . WEPA was been found to have a pH of between 11.7 and 12.1 which is slightly greater than the pH of aqueous K 2 CO 3 solution .…”

“…WEPA was been found to have a pH of between 11.7 and 12.1 which is slightly greater than the pH of aqueous K 2 CO 3 solution . The ash and its water extract were subjected to X‐ray photoelectron spectroscopy (XPS) and energy‐dispersive X‐ray spectroscopy (EDS) analyses, and found to consist of a high amount of potassium and considerable amount of calcium and magnesium (K:Ca:Mg ratio of 86.9:7.6:5.5) along with carbon, chlorine and oxygen . The basic nature of the extract has been assumed because of the presence of metal (such as K, Mg and Ca) oxides and carbonates.…”

“…The formation of 3a in 82, 68, 52 and 76% yields in 20, 30, 80 and 20 min (Table , entries 13–16) was identified, which indicates WEPA is the best among these media. This may be due to the presence of a large quantity of potassium and potassium may exist in the form of carbonates or oxides . The XPS data for ash of sweet lemon peel (provided in the supporting information) also suggest the presence of potassium, magnesium and calcium with a ratio of 50.2:12.4:37.4 along with carbon, chlorine and oxygen.…”

“…We adopted a similar procedure for the preparation of WESLA to that used in the case of WEPA . Sweet lemon peels were washed with distilled water to remove impurities and were cut into small pieces.…”

Added catalyst-free, versatile and environment beneficial bromination of (hetero)aromatics using NBS in WEPA

“…The nuclear bromination of aromatic or heteroaromatic compounds is the frequently used transformation in making highly reactive aryl/heteroaryl bromides. These bromides are the principal substrates in the synthesis of biaryls, aryl amines, organometallics, cinnamate esters, functional materials and diverse biologically effective organics [1][2][3][4][5][6][7]. By virtue of this essentiality a sizeable efforts have been appeared in the literature for the preparation of aryl bromides and heteroaryl bromides.…”