Advances in Heterocyclic Chemistry, Volume 138, the latest release in this definitive series on the field of heterocyclic chemistry, combines descriptive synthetic chemistry and mechanistic insights to yield an understanding on how chemistry drives the preparation and useful properties of heterocyclic compounds. Topics in this new release include The Paal Knorr reaction in Heterocyclic Chemistry, Synthesis and Applications of Heterocyclic Sulfoximines, Recent advances in the synthesis of 4H-chromen-4-ones (2012-2021), Recent Developments in the Chemistry of Heteroporphyrins and Heterocarbaporphyrins, The Chemistry of 1,4-Dihydropyrrolo[3,2-b]pyrroles, and more.