page_title: Nazarov cyclization reaction
section_title: Imino-Nazarov reaction
hierarchical_section_title: Nazarov cyclization reaction / Related Reactions / Imino-Nazarov reaction
caption_attribution_description: English: Imino-Nazarov cyclization
context_page_description: The Nazarov cyclization reaction is a chemical reaction used in organic chemistry for the synthesis of cyclopentenones. The reaction is typically divided into classical and modern variants, depending on the reagents and substrates employed. It was originally discovered by Ivan Nikolaevich Nazarov in 1941 while studying the rearrangements of allyl vinyl ketones.
  As originally described, the Nazarov cyclization involves the activation of a divinyl ketone using a stoichiometric Lewis acid or protic acid promoter. The key step of the reaction mechanism involves a cationic 4π-electrocyclic ring closure which forms the cyclopentenone product. As the reaction has been developed, variants involving substrates other than divinyl ketones and promoters other than Lewis acids have been subsumed under the name Nazarov cyclization provided that they follow a similar mechanistic pathway.
  The success of the Nazarov cyclization as a tool in organic synthesis stems from the utility and ubiquity of cyclopentenones as both motifs in natural products and as useful synthetic intermediates for total synthesis. The reaction has been used in several total syntheses and several reviews have been published.
context_section_description: Nitrogen analogues of the Nazarov cyclization reaction (known as imino-Nazarov cyclization reactions) have few instances; there is one example of a generalized imino-Nazarov cyclization reported (shown below), and several iso-imino-Nazarov reactions in the literature. Even these tend to suffer from poor stereoselectivity, poor yields, or narrow scope. The difficulty stems from the relative over-stabilization of the pentadienyl cation by electron donation, impeding cyclization.
caption: Imino-Nazarov cyclization
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