Moore cyclization

Scheme 25. Synthesis of terreic acid via Moore cyclization...

This reaction was first reported by Moore in 1985. It is a synthesis of phenol (or quinone) derivatives by means of the thermal cyclization of enyne-ketenes between C2 and Cy via an aryl/phenoxy biradical intermediate. Therefore, it is generally known as the Moore cyclization. Occasionally, it is directly referred to as the Moore reaction. 

Other references related to the Moore cyclization are cited in the literature. ... 

This reaction is related to the Bergman Cyclization, Moore Cyclization, and Myers-Saito Cyclization. 

Moore Myers Cyclization Moore Cyclization Myers Cyclization... 

Moore cyclization is formulated as a cyclization of enyne-ketenes 1 to diradicals 2. This process usually proceeds by thermal induction, leading to the formation of a benzene ring. 

Enediynyl ethyl ethers like 12 have been applied by Wang s group as precursors of enyne-ketenes 13, which underwent the Moore cyclization reaction to form diradicals. The intermediate 14 and (after 1,5-hydrogen shift) new diradical 15, form, upon the cascade transformations, the final products mainly chromanol 16 and spiro ketone 17. The latter is a result of subsequent intramolecular reaction of intermediates o-quinones methide and spiro ketone (not illustrated). ... 

Another example of the application of the chromium carbene complex for the synthesis of benzannulated compounds was described by Herndon and Wang." The coupling of substituted carbene chromium complex 27 with conjugated enediyne 28 results in the formation of intermediate enyne-ketene 29, which undergoes the Moore cyclization to produce the intermediate chromium-complexed diradical 30. The... 

The Myers-Saito cyclization was first described independently in 1989 by Isao Saito (Kyoto University, Japan) and Andrew G. Myers (California Institute of Technology, Pasadena) whose findings were submitted for publication on June 7 and June 12, respectively. As a parallel transformation to the Moore cyclization (Chapter 4.12), in which an allenic fragment replaces the ketene moiety in the substrate, the Myers-Saito reaction provides a path to carbon diradicals. In its pioneering version, the reaction involved the cyclization of (Z)-l,2,4-heptatrien-6-yne (enyne-allene) 3, or its phosphine oxide derivative 5, to substituted a,3-dehydrotoluene diradicals, and subsequently to toluene derivatives 4 and 6. The reaction proceeds under thermal neutral conditions in 1,4-cyclohexadiene or other organic solvents such as methanol or carbon tetrachloride. 

In the cases where R is an ethoxyl group, thermolysis at 132 C induced a retro-ene reaction with the elimination of an ethylene to generate enyne-ketenes. Specifically, 72a was converted to the enyne-ketene 73, which then underwent a Moore cyclization reaction to form the biradical 74 (Scheme 17) (27). A 1,5-hydrogen shift afforded the biradical 75, which decayed via intramolecular routes to give the chromanol 76, the phenols 77 and 78, and the spiro ketone 79. 

Kitahara, Y., T. Kato, T. Kobayashi, and B. P. Moore Cyclization of polyenes. XVII. Synthesis and pheromone activity of d,l-neocembrene. Chem. Lett. 1976, 219—222. 

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