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A heterogeneous gold catalyst with remarkable activity for promoting the electrophilic reactions of aryl vinyl ketones and aryl dienyl ketones is described. The catalyst is easy to prepare, is robust, and can be recycled. Low loadings are effective for different types of cationic reactions, including Nazarov cyclizations, lactonizations, and [1,2] shifts.

A reaction sequence involving the 1,6-conjugate addition of a nucleophile to a dienyl diketone followed by Nazarov cyclization is described. Several nucleophiles are identified as competent initiators for the sequence. A different reaction outcome is observed when catalytic amounts of nucleophile are employed, involving elimination of the nucleophile after the electrocyclization. [ABSTRACT FROM AUTHOR]

The article describes the total syntheses of aglafolin, rocagloic acid, and rocaglamide using Nazarov cyclization. According to the authors, the generation of the necessary oxyallyl cation intermediate was accomplished via peracid oxidation of an allenol ether to generate an unusual oxycarbenium ion species that undergoes cyclization. Moreover, it mentions that the synthesis is efficient, highly diastereoselective, and strategically distinct from previous syntheses of rocaglamide.

This article presents a study on the efficient catalysis of Nazarov cyclization using a cationic iridium complex possessing adjacent labile coordination sites. The formation of five-membered carbocycles in natural products and bioactive molecules has stimulated interest in utilizing Nazarov cyclization strategies for their synthesis. This reaction is a 4π electrocyclization that can convert divinyl ketones into cyclopentenones stereoselectively via conrotatory cyclization. The Nazarov cyclization is generally promoted by one or more equivalents of a protic or Lewis acid and most often involves the intermediacy of a 3-oxypentadienyl cation.

Review: 57 refs. [ABSTRACT FROM AUTHOR]

This article describes the evolution of a Nazarov cyclization-based synthetic strategy targeting the anticancer, anti-inflammatory, and insecticidal natural products (±)-rocaglamide. Initial pursuit of a polarized heteroaromatic Nazarov cyclization to construct the congested cyclopentane core revealed an unanticipated electronic bias in the pentadienyl cation. This reactivity was hamessed in a successful second-generation approach using an oxidation-initiated Nazarov cylization of a heteroaryl alkoxyallene. Full details of these two approaches are giving, as well as the characterization of undesired reaction pathways available to the Nazarov cyclization product. A sequence of experiments that led to an understanding of the unexpected reactivity of this key intermediate is described, which culminated in the successful total synthesis of (+)-rocaglamide. [ABSTRACT FROM AUTHOR]

The impact of dienone substitution on the Nazarov cyclization has been examined in detail. Substrates bearing different substituents at each of four positions on the dienone backbone were systematically probed in order to identify trends leading to higher reactivity and better selectivity. Desymmetrization of the pentadienyl cation and oxyallyl cation intermediates through placement of polarizing groups at both the C-2 and C-4 positions was found to be particularly effective. These modifications allowed cyclizations to occur in the presence of catalytic amounts of mild Lewis acids. It was also found that stereoconvergent cyclization of mixtures of E and Z isomers of alkylidene β-ketoesters occurred via an efficient isomerization process that occurred under the reaction conditions. [ABSTRACT FROM AUTHOR]