1. Synthesis of Spirocyclic and Fused Cyclic Compounds by Transition-Metal-Catalyzed Intramolecular Friedel-Crafts-Type Reactions of Phenol Derivatives.
- Author
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Tetsuhiro Nemoto and Yasumasa Hamada
- Subjects
CYCLIC compounds ,TRANSITION metal catalysts ,FRIEDEL-Crafts reaction ,PHENOL derivatives ,CHEMICAL synthesis ,AROMATIZATION - Abstract
This account describes the development of novel dearomatization reactions of phenols using transition-metal-catalyzed ipso-Friedel-Crafts-type processes. In general, phenols function as O-nucleophiles in transition-metal-catalyzed allylic substitution reactions, providing the corresponding aryl ethers. We found that, however, an intramolecular ipso-Friedel-Crafts allylic alkylation of phenols proceeded smoothly in the presence of a palladium catalyst, producing various spiro[4.5]cyclohexadienone derivatives. This finding led us to launch detailed investigations into this type of reaction. Pd-catalyzed intramolecular Friedel-Crafts allylic alkylation of phenols was next examined to synthesize 10-vinyl 9,10-dihydrophenanthrene derivatives. This reaction was successfully extended to a catalytic asymmetric process. We also developed a novel synthetic method for spiro[5.5]cyclohexadienones based on a Pd-catalyzed intramolecular ipso-Friedel-Crafts-type addition of phenols to ç3-propargylpalladium(II) intermediates. Mechanistic studies revealed that the present reaction proceeds through a rearomatization-assisted oxidative addition. Moreover, a Au-catalyzed intramolecular ipso-Friedel-Crafts alkenylation of phenols with a terminal alkyne is discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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