Highly economic and waste valorization strategy for multicomponent and Knoevenagel reactions using water extract of tamarind seed ash.

The application of solid organic waste-originated products in the preparation of synthetically and biologically significant compounds in aqueous media or pure water is a highly desired task in chemical synthesis that shows an effective solution to the circular economy and sustainable environment. In this article, we describe our research on the development of highly economic and sustainable protocols for the synthesis of biologically important oxygen-heterocycles (using a multicomponent reaction) and synthetically important olefins (via the Knoevenagel condensation reaction) using water extract of tamarind seed ash (WETS) as catalyst and aqueous reaction medium. The reactions are carried out at room temperature (RT) under toxic/problematic/volatile organic solvent-free conditions. Products of the current methods have been purified by using recrystallization technique. WETS was characterized from its FTIR, powder XRD, SEM, and EDAX data. Problematic and non-renewable solvents were avoided throughout the process from their synthesis to purification. The utilization of solid organic waste-originated catalyst and aqueous media, avoid of non-renewable substances as catalysts, media, separation solvents and promoters, and unobligating heating conditions can surely attract the attention of chemists towards exploring the waste-based products in chemical transformations.

Porphyrin N-Pincer Pd(II)-Complexes in Water: A Base-Free and Nature-Inspired Protocol for the Oxidative Self-Coupling of Potassium Aryltrifluoroborates in Open-Air.

Metalloporphyrins (and porphyrins) are well known as pigments of life in nature, since representatives of this group include chlorophylls (Mg-porphyrins) and heme (Fe-porphyrins). Hence, the construction of chemistry based on these substances can be based on the imitation of biological systems. Inspired by nature, in this article we present the preparation of five different porphyrin, meso-tetraphenylporphyrin (TPP), meso-tetra(p-anisyl)porphyrin (TpAP), tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (TSTpSPP), meso-tetra(m-hydroxyphenyl)porphyrin (TmHPP), and meso-tetra(m-carboxyphenyl)porphyrin (TmCPP) as well as their N-pincer Pd(II)-complexes such as Pd(II)-meso-tetraphenylporphyrin (PdTPP), Pd(II)-meso-tetra(p-anisyl)porphyrin (PdTpAP), Pd(II)-tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (PdTSTpSPP), Pd(II)-meso-tetra(m-hydroxyphenyl)porphyrin (PdTmHPP), and Pd(II)-meso-tetra(m-carboxyphenyl)porphyrin (PdTmCPP). These porphyrin N-pincer Pd(II)-complexes were studied and found to be effective in the base-free self-coupling reactions of potassium aryltrifluoroborates (PATFBs) in water at ambient conditions. The catalysts and the products (symmetrical biaryls) were characterized using their spectral data. The high yields of the biaryls, the bio-mimicking conditions, good substrate feasibility, evading the use of base, easy preparation and handling of catalysts, and the application of aqueous media, all make this protocol very attractive from a sustainability and cost-effective standpoint.

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

A bio-derived sustainable medium based on water extract of pomegranate ash (WEPA) has, for the first time, been developed for the homocoupling of aryl halides under palladium-assistance. Avoiding the requirement of an external base, ligand and π-acid, the use of the proposed renewable medium offers remarkable attributes like wide substrate scope, good to nearly quantitative yields of biphenyls with exceptional chemoselectivity and scale up viability.