Computational studies of the mechanism of Pd-Catalyzed Intramolecular Friedel–Crafts allylic alkylation of phenols. Issue 18 (1st May 2020)

• Record Type: Journal Article
• Authors: Kuribara, Takahito; Matsumoto, Koki; Nagasawa, Sho; Suzuki, Yuta; Nakajima, Masaya; Hamada, Yasumasa; Nemoto, Tetsuhiro
• Is Part Of: Tetrahedron. Volume 76:Issue 18(2020)
• Publication Date: 2020-05-01
• Subjects: DFT -- Dearomatization -- Palladium; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2020.131146
• Languages: English
• ISSNs: 0040-4020

Abstract

Abstract: We previously reported a synthetic method of spirocyclohexadienones using an Pd-catalyzed intramolecular ipso-Friedel–Crafts allylic alkylation of para-substituted phenol derivatives. However, the mechanism for the step leading to spirocyclization and driving force behind the remarkably easier formation of the five-membered spirocyclohexadienone as compared with the six-membered spirocyclohexadienone were unclear. Herein, detailed density functional theory (DFT) calculations for the spirocyclization were performed to obtain a plausible reason for the observed behavior. In addition, the mechanistic basis of the characteristic ortho-selectivity in the related Pd-catalyzed intramolecular Friedel–Crafts allylic alkylation of meta-substituted phenol derivatives was elucidated. DFT calculations and experimental studies revealed that the ortho-selective allylation proceeded via an unexpected eleven-membered oxapalladacycle-mediated intramolecular Friedel–Crafts type process. Graphical abstract: Image 1 Highlights: DFT calculations for the Pd-catalyzed phenol dearomatization were performed. DFT calculations for the developed Friedel-Crafts type reaction were performed. DFT calculations and experimental studies revealed the plausible reaction pathway.