Nazarov cyclization reaction

Nazarov cyclization
Named after	Ivan Nikolaevich Nazarov
Reaction type	Ring forming reaction
Identifiers
Organic Chemistry Portal	nazarov-cyclization
RSC ontology ID	RXNO:0000209

The Nazarov cyclization reaction (often referred to as simply the Nazarov cyclization) 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 (1906–1957) 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 (See Mechanism below). 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 (including jasmone, the aflatoxins, and a subclass of prostaglandins) and as useful synthetic intermediates for total synthesis. The reaction has been used in several total syntheses and several reviews have been published.

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