Heterocycle Formation

A heterocyclic compound is a cyclic compound that has at least one element other than carbon, e.g., nitrogen, oxygen, or sulfur, as part of its ring structure. Its general structure resembles that of cyclic organic compounds that contain only carbon. However, the presence of heteroatoms gives heterocyclic compounds distinct physical and chemical properties.

One of the earliest named reactions in this category was discovered in 1882 by A. Hantzsch, who condensed two equivalents of ethyl acetoacetate with one of acetaldehyde and ammonia to obtain a fully substituted symmetrical dihydropyridine.

• Fischer indole synthesis
• Hantzsch dihydropyridine synthesis
• Knorr pyrrole synthesis
• Pictet-Spengler tetrahydroisoquinoline synthesis
• Pomeranz-Fritsch reaction