Metal-Free and Sustainable Strategies in the Synthesis of Substituted Furans: A Contemporary Review

Furans and their derivatives play an important role in synthetic organic chemistry and biological chemistry, and they serve as key structural units in numerous natural products. In recent times, environmentally benign synthetic processes have emerged as a vital strategy for the production of fine organic chemicals. This review article summarises recent advances in various transition metal-free, sustainable synthetic methodologies for the synthesis of substituted furans. The focus is placed on literature reports published during the past five years (2020–2025). Various synthetically important methodologies—such as catalytic methods, cycloaddition reactions, and multicomponent reactions—used to prepare substituted furan scaffolds have been critically reviewed. Particular emphasis has been placed on metal-free methods that adhere to the principles of Green Chemistry.