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Relevant academic research and scientific papers

Chiral Brosted acids in the catalytic asymmetric nazarov cyclization - The first enantioselective organocatalytic electrocyclic reaction

(Chemical Equation Presented) Low catalyst loadings, high enantioselectivities, mild conditions, and fast reaction times are the important features of the first enantioselective organocatalytic electrocyclic reaction: a Nazarov cyclization leading to the

Natural deep eutectic solvents as an efficient and reusable active system for the Nazarov cyclization

Natural deep eutectic solvents have emerged as alternative non-toxic, non-aqueous solvents for an increasing number of synthetic transformations. Remarkably, in some cases one (or more) components of the NaDES plays an active role in the reaction mechanism and directly participates as either a catalyst or a reagent in the reaction. In this paper, we tested several NaDESs in which one of the components is a carboxylic acid as a medium to perform the Nazarov cyclization of divinyl ketones to obtain cyclopentenones, a widespread motif in natural compounds. The reaction conditions were optimized and the scope was investigated on C-, O- A nd N-derived compounds. To assess the full sustainability of the proposed approach, the recyclability and scalability of the process were investigated, thus proving that multi-gram preparations are possible with complete recycling of the medium.

Iodine-Catalyzed Nazarov Cyclizations

The Nazarov cyclization is an important pericyclic reaction that allows the synthesis of substituted cyclopentenones. We now demonstrate that this reaction can be performed under very mild, metal-free reaction conditions using molecular iodine as the catalyst. A variety of different divinyl ketones including aromatic systems undergo the iodine-catalyzed reaction with moderate to very good yields in both polar and apolar solvents. Our mechanistic studies indicate that the Nazarov system is activated through a halogen bond between the carbonyl group and the catalyst, and other modes of action like Br?nsted acid or iodonium ion catalysis are unlikely. Furthermore, addition of iodine to the double bond or a putative iodine-catalyzed cis-trans isomerization of the employed olefins seem not to be an important side reaction here.

2,2′-Biphenol/B(OH)3 catalyst system for Nazarov cyclization

A novel catalyst system—a combination of the readily available 2,2′-biphenol with the inexpensive, nontoxic, and eco-friendly B(OH)3—promoted the Nazarov cyclization of activated and inactivated divinyl ketones to afford the corresponding cyclo

Hydroxylamine catalyzed Nazarov cyclizations of divinyl ketones Dedicated to Professor Hilton Weiss on his 80th birthday

The first examples of iminium catalyzed Nazarov cyclizations of divinyl ketones are presented. Experiments describing hydroxylamine catalysis of the cyclization of eight α-alkoxy divinyl ketones (60-79% yield) and one unactivated divinyl ketone (38% yield) are reported. Phenyl substitution at the β-position of the divinyl ketone inhibits cyclization, whereas β-alkyl substituted α-alkoxy divinyl ketones readily cyclize.

A mild, catalytic and efficient Nazarov cyclization mediated by phosphomolybdic acid

A mild, selective and efficient Nazarov cyclization of divinyl ketones catalyzed by phosphomolybdic acid (PMA) is described. The process demonstrates a broad substrate scope with functional group tolerance under short reaction times. PMA supported on silica gel is more efficient than the bulk catalyst and is recycled up to three times without significant activity loss.

Reagent-free Nazarov cyclisations

A new protocol for Nazarov cyclisation is described that involves simple heating of dienones in the absence of any external Lewis acid. The Royal Society of Chemistry 2005.

Efficient Nazarov Cyclizations of 2-Alkoxy-1,4-pentadien-3-ones

(Equation presented) Expeditious and high-yielding Nazarov cyclizations of 2-alkoxy-1,4-pentadien-3-ones are described. An example of a catalytic asymmetric Nazarov cyclization is presented.