Seven-Membered Rings

New synthetic methods to prepare seven-membered heterocyclic compounds containing one, two, or three of the heteroatoms N, O or S are covered. Aromatic systems containing at least one N atom have been the focus of many reports. Research was often driven by a desire to prepare these heterocycles in a stereo-controlled fashion, the search for new bioactive heterocycles for use in medicinal chemistry, and for the synthesis of natural products. Notable synthetic methods included include transition metal-catalyzed, cycloaddition/ annulation, cascade, and C–H functionalization processes. A number of useful reviews in the field were also published.