Nazarov-like cyclization reactions

The Nazarov cyclization, a well-known method for the formation of cyclopentenones, mechanistically involves the 4 pi electrocyclization of a 1,4-pentadienyl cation, generated from cross-conjugated divinyl ketones. Recently, advances related to this cyclization, such as the incorporation of heteroatoms as well as the use of cyclopropanes as double bond equivalents have extended the scope of the original reaction. The modifications discussed in this review, which covers the years 2009-2013, have allowed the realization of both heteroatom-and homo-Nazarov cyclizations.