Advances in Heterocyclic Chemistry, Volume 125 is the definitive series in the field - one of great importance to organic chemists, polymer chemists, and many biological scientists. Because biology and organic chemistry increasingly intersect, the associated nomenclature is being used more frequently in explanations. Topics in this updated release explore Diketene as Privileged Synthon in the Synthesis of Heterocycles. Part 2: Six-Membered Ring Heterocycles, Recent Advances in the Synthesis of Piperidines: Functionalization of Preexisting Ring Systems, Indazoles: Synthesis and Bond-Forming Heterocyclization, and The Chemistry of Sulfur Containing [5,5]-Fused Ring Systems with a Bridgehead Nitrogen. Written by established authorities in the field from around the world, this comprehensive review combines descriptive synthetic chemistry and mechanistic insights to yield an understanding of how chemistry drives the preparation and useful properties of heterocyclic compounds.