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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Yasumasa Hamada and Tetsuhiro Nemoto
- Subjects
chemistry.chemical_classification ,Substitution reaction ,Allylic rearrangement ,010405 organic chemistry ,education ,Organic Chemistry ,Alkyne ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Tsuji–Trost reaction ,chemistry ,Cascade reaction ,Intramolecular force ,Propargyl ,Organic chemistry ,Friedel–Crafts reaction - 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 η3-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. 1 Introduction 2 Pd-Catalyzed Intramolecular Friedel–Crafts Allylic Alkylation of Phenols 2.1 Synthesis of Spirocyclohexadienone Derivatives by Pd-Catalyzed Intramolecular ipso-Friedel–Crafts Allylic Alkylation of Phenols 2.2 Mechanistic Considerations 2.3 Application to Cascade Reaction Processes 2.4 Asymmetric Synthesis of Dihydrophenanthrene Derivatives by Pd-Catalyzed Asymmetric Intramolecular Friedel–Crafts Allylic Alkylation of Phenols 3 Dearomatization of Phenols by Activation of Propargyl Carbonates with a Pd Catalyst 4 Au-Catalyzed Intramolecular ipso-Friedel–Crafts Alkenylation of Phenols 5 Summary and Outlook
- Published
- 2016