3.1.2.2 Formation of Heterocycles

AbstractThe formation of heterocycles through the Heck cross-coupling reaction has been studied extensively as it allows potential efficient access to a large variety of compounds. High-yielding production of heterocyclic frameworks is of paramount importance in natural product based research as well as in medicinal chemistry programs. In particular, the intramolecular Heck reaction has been used extensively for this purpose. Cyclization methods producing the five-membered pyrrole ring contained within the indole ring system are by far the most common, possibly due to the plethora of such compounds found in nature and their corresponding biological activity. In most examples discussed in this chapter, the mechanism by which the intramolecular Heck cross coupling operates is through the standard oxidative addition, migratory insertion, C—C bond rotation, syn-β-hydride elimination, and reductive elimination pathway. However, sometimes this “standard” Mizoroki–Heck catalytic cycle is not always followed, and rare examples such as anti-elimination or oxidative Heck reaction (intramolecular Fujiwara–Moritani reaction) are further emphasized when they arise.