Andreev IA, Ratmanova NK, Augustin AU, Ivanova OA, Levina II, Khrustalev VN, Werz DB, Trushkov IV. Protic Ionic Liquid as Reagent, Catalyst, and Solvent: 1-Methylimidazolium Thiocyanate.
Angew Chem Int Ed Engl 2021;
60:7927-7934. [PMID:
33433034 PMCID:
PMC8048580 DOI:
10.1002/anie.202016593]
[Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Indexed: 02/06/2023]
Abstract
We propose a new concept of the triple role of protic ionic liquids with nucleophilic anions: a) a regenerable solvent, b) a Brønsted acid inducing diverse transformations via general acid catalysis, and c) a source of a nucleophile. The efficiency of this strategy was demonstrated using thiocyanate-based protic ionic liquids for the ring-opening of donor-acceptor cyclopropanes. A wide variety of activated cyclopropanes were found to react with 1-methylimidazolium thiocyanate under mild metal-free conditions via unusual nitrogen attack of the ambident thiocyanate ion on the electrophilic center of the three-membered ring affording pyrrolidine-2-thiones bearing donor and acceptor substituents at the C(5) and C(3) atoms, respectively, in a single time-efficient step. The ability of 1-methylimidazolium thiocyanate to serve as a triplex reagent was exemplarily illustrated by (4+2)-annulation with 1-acyl-2-(2-hydroxyphenyl)cyclopropane, epoxide ring-opening and other organic transformations.
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