Impact of the Valence Charge of Transition Metals on the Cobalt- and Rhodium-Catalyzed Synthesis of Indenamines, Indenols, and Isoquinolinium Salts: A Catalytic Cycle Involving MIII/MV [M = Co, Rh] for [4 + 2] Annulation

Mong-Feng Chiou; Jayachandran Jayakumar; Chien-Hong Cheng; Shih-Ching Chuang

doi:10.1021/acs.joc.8b00711

Impact of the Valence Charge of Transition Metals on the Cobalt- and Rhodium-Catalyzed Synthesis of Indenamines, Indenols, and Isoquinolinium Salts: A Catalytic Cycle Involving M^III/M^V [M = Co, Rh] for [4 + 2] Annulation

J Org Chem. 2018 Aug 3;83(15):7814-7824. doi: 10.1021/acs.joc.8b00711. Epub 2018 Jun 22.

Authors

Mong-Feng Chiou¹, Jayachandran Jayakumar², Chien-Hong Cheng², Shih-Ching Chuang¹

Affiliations

¹ Department of Applied Chemistry , National Chiao Tung University , Hsinchu 30010 , Taiwan.
² Department of Chemistry , National Tsing Hua University , Hsinchu 30010 , Taiwan.

PMID: 29896964
DOI: 10.1021/acs.joc.8b00711

Abstract

Reaction mechanisms for the synthesis of indenamines, indenols, and isoquinolinium salts through cobalt- and rhodium-catalysis were investigated using density functional theory calculations. We found that the valence charge of transition metals dramatically influences the reaction pathways. Catalytic reactions involving lower-oxidation-state transition metals (M^I/M^III, M = Co and Rh) generally favor a [3 + 2] cyclization pathway, whereas those involving higher oxidation states (M^III/M^V) proceed through a [4 + 2] cyclization pathway. A catalytic cycle with novel M^III/M^V as a crucial species was successfully revealed for isoquinolinium salts synthesis, in which highly valent M^V was encountered not only in the [RhCp*]-catalysis but also in the [CoCp*]-catalysis.