Ashes from organic waste as reagents in synthetic chemistry: a review

Abstract

The decline of fossil- and ore-based materials is calling for more recycling of waste into new materials. Here, I review the recycling of ashes from biomass into reagents for chemical synthesis and biodiesel production. Biomass includes banana, pomegranate, rice, papaya, century plant, water hyacinth, bael fruit, nilgiri, mango, onion, muskmelon fruit, pomelo, lemon fruit, teak and tamarind. Chemical reactions include Knoevenagel condensation, Suzuki–Miyaura cross-coupling, Sonogashira reaction, Dakin reaction, Henry reaction, Ullmann coupling, Pd-catalyzed homocoupling, aromatic bromination, hydroxylation of arylboronic acids, hydration of nitriles and azide–alkyne click reaction. The synthesis of peptide bonds, disulfides, aminochromenes, carboxycoumarins, diazohydroxy esters, imidazopyridines, pyranopyrazoles, chalcones, flavones and bisenols is described.