Singh S, Mondal S, Tiwari V, Karmakar T, Hazra CK. Cooperative Friedel-Crafts Alkylation of Electron-Deficient Arenes via Catalyst Activation with Hexafluoroisopropanol.
Chemistry 2023;
29:e202300180. [PMID:
36680470 DOI:
10.1002/chem.202300180]
[Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 01/20/2023] [Accepted: 01/20/2023] [Indexed: 01/22/2023]
Abstract
A Friedel-Crafts alkylation of electron-deficient arenes with aldehydes through ''catalyst activation'' is presented. Through hydrogen bonding interactions, the solvent 1,1,1,3,3,3, -hexafluoroisopropanol (HFIP) interacted with the added Brønsted acid catalyst pTSA•H2 O, increasing its acidity. This activated catalyst enabled the Friedel-Crafts alkylation of electron-neutral as well as electron-deficient arenes. Strongly electron withdrawing arenes including arenes with multiple halogen atoms, NO2 , CHO, CO2 R, and CN, groups acted as efficient nucleophiles in this reaction. DFT studies reveal multiple roles of solvent HFIP viz; increasing the Brønsted acidity of the catalyst pTSA•H2 O, and stabilization of the transition states through a concerted pathway enabling the challenging reaction.
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