Synthetic Strategies Toward N‐Functionalized Cyclens

Cyclen (1,4,7,10‐tetraazadodecane) is a widely used building block in the synthesis of many important molecules with applications spanning MRI contrast agents, fluorescent probes and heavy metals sensors. This review describes the various synthetic methodologies employed for the preparation of N ‐functionalized cyclens such as: synthesis from acyclic precursors; alkylation or acylation of cyclen; and protecting group manipulations. Emphasis is given to synthetic strategies allowing for the selective, differential N ‐functionalization of cyclen which is particularly useful for many modern applications.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)