Iron-Catalyzed Photoinduced LMCT: a 1° C-H Abstraction Enables Skeletal Rearrangements and C(sp)-H Alkylation

Overview

Journal ACS Catal

Publisher American Chemical Society

Date 2022 Jun 7

PMID 35669035

Authors

Yi Cheng Kang

Sean M Treacy

Tomislav Rovis

Affiliations

Soon will be listed here.

Abstract

Herein we disclose an iron-catalyzed method to access skeletal rearrangement reactions akin to the Dowd-Beckwith ring expansion from unactivated C(sp)-H bonds. Photoinduced ligand-to-metal charge transfer at the iron center generates a chlorine radical, which abstracts electron-rich C(sp)-H bonds. The resulting unstable alkyl radicals can undergo rearrangement in the presence of suitable functionality. Addition to an electron deficient olefin, recombination with a photoreduced iron complex, and subsequent protodemetallation allows for redox-neutral alkylation of the resulting radical. Simple adjustments to the reaction conditions enable the selective synthesis of the directly alkylated or the rearranged-alkylated products. As a radical clock, these rearrangements also enable the measurement of rate constants of addition into various electron deficient olefins in the Giese reaction.

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References

Kim Y, Kim D . Electrochemical Radical Selenylation/1,2-Carbon Migration and Dowd-Beckwith-Type Ring-Expansion Sequences of Alkenylcyclobutanols. Org Lett. 2019; 21(4):1021-1025. DOI: 10.1021/acs.orglett.8b04041. View

Song Z, Fan C, Tu Y . Semipinacol rearrangement in natural product synthesis. Chem Rev. 2011; 111(11):7523-56. DOI: 10.1021/cr200055g. View

Hu A, Guo J, Pan H, Zuo Z . Selective functionalization of methane, ethane, and higher alkanes by cerium photocatalysis. Science. 2018; 361(6403):668-672. DOI: 10.1126/science.aat9750. View

Hudzik J, Bozzelli J . Thermochemistry and bond dissociation energies of ketones. J Phys Chem A. 2012; 116(23):5707-22. DOI: 10.1021/jp302830c. View

Ardura D, Sordo T . Three-carbon Dowd-Beckwith ring expansion reaction versus intramolecular 1,5-hydrogen transfer reaction: a theoretical study. J Org Chem. 2005; 70(23):9417-23. DOI: 10.1021/jo051551g. View

Beckwith A, Poole J . Factors affecting the rates of addition of free radicals to alkenes-determination of absolute rate coefficients using the persistent aminoxyl method. J Am Chem Soc. 2002; 124(32):9489-97. DOI: 10.1021/ja025730g. View

Yi H, Zhang G, Wang H, Huang Z, Wang J, Singh A . Recent Advances in Radical C-H Activation/Radical Cross-Coupling. Chem Rev. 2017; 117(13):9016-9085. DOI: 10.1021/acs.chemrev.6b00620. View

Jung M, Piizzi G . gem-disubstituent effect: theoretical basis and synthetic applications. Chem Rev. 2005; 105(5):1735-66. DOI: 10.1021/cr940337h. View

Overman L . Molecular Rearrangements in the Construction of Complex Molecules. Tetrahedron. 2010; 65(33):6432-6446. PMC: 2902795. DOI: 10.1016/j.tet.2009.05.067. View

10.

Bachrach S . The gem-dimethyl effect revisited. J Org Chem. 2008; 73(6):2466-8. DOI: 10.1021/jo702665r. View

11.

Karkas M, Porco Jr J, Stephenson C . Photochemical Approaches to Complex Chemotypes: Applications in Natural Product Synthesis. Chem Rev. 2016; 116(17):9683-747. PMC: 5025835. DOI: 10.1021/acs.chemrev.5b00760. View

12.

Perry I, Brewer T, Sarver P, Schultz D, DiRocco D, MacMillan D . Direct arylation of strong aliphatic C-H bonds. Nature. 2018; 560(7716):70-75. PMC: 6192026. DOI: 10.1038/s41586-018-0366-x. View

13.

Duecker F, Heinze R, Heretsch P . Synthesis of Swinhoeisterol A, Dankasterone A and B, and Periconiastone A by Radical Framework Reconstruction. J Am Chem Soc. 2019; 142(1):104-108. DOI: 10.1021/jacs.9b12899. View

14.

Chen Z, Zhang X, Tu Y . Radical aryl migration reactions and synthetic applications. Chem Soc Rev. 2015; 44(15):5220-45. DOI: 10.1039/c4cs00467a. View

15.

Lemek T, Mayr H . Electrophilicity parameters for benzylidenemalononitriles. J Org Chem. 2003; 68(18):6880-6. DOI: 10.1021/jo0344182. View

16.

Liu Y, Yeung Y . Synthesis of Macrocyclic Ketones through Catalyst-Free Electrophilic Halogen-Mediated Semipinacol Rearrangement: Application to the Total Synthesis of (±)-Muscone. Org Lett. 2017; 19(6):1422-1425. DOI: 10.1021/acs.orglett.7b00350. View

17.

Chirik P, Morris R . Getting Down to Earth: The Renaissance of Catalysis with Abundant Metals. Acc Chem Res. 2015; 48(9):2495. DOI: 10.1021/acs.accounts.5b00385. View

18.

Ringer A, Magers D . Conventional strain energy in dimethyl-substituted cyclobutane and the gem-dimethyl effect. J Org Chem. 2007; 72(7):2533-7. DOI: 10.1021/jo0624647. View