Diels–Alder cycloaddition reaction is one of the most powerful strategies for the construction of six-membered carbocyclic and heterocyclic systems, in most cases with high regio- and stereoselectivity. In this review, an insight into the most relevant advances on sustainable Diels–Alder reactions since 2010 is provided. Various environmentally benign solvent systems are discussed, namely bio-based derived solvents (such as glycerol and gluconic acid), polyethylene glycol, deep eutectic solvents, supercritical carbon dioxide, water and water-based aqueous systems. Issues such as method’s scope, efficiency, selectivity and reaction mechanism, as well as sustainability, advantages and limitations of these reaction media, are addressed.

The 1,3-dipolar cycloaddition reaction is a powerful and versatile strategy for the synthesis of carbocyclic and heterocyclic five-membered rings. Herein, the most recent developments on the [3+2] cycloaddition reactions using allenes acting either as dipolarophiles or 1,3-dipole precursors, are highlighted. The recent contributions on the phosphine- and transition metal-catalyzed [3+2] annulations involving allenes as substrates are also covered, with the exception of those in which the formation of a 1,3-dipole (or synthetic equivalent) is not invoked. This review summarizes the most relevant research in which allenes are used as building blocks for the construction of structurally diverse five-membered rings via [3+2] annulation reactions.