Scheidt F, Thiehoff C, Yilmaz G, Meyer S, Daniliuc CG, Kehr G, Gilmour R. Fluorocyclisation via I(I)/I(III) catalysis: a concise route to fluorinated oxazolines.
Beilstein J Org Chem 2018;
14:1021-1027. [PMID:
29977374 PMCID:
PMC6009682 DOI:
10.3762/bjoc.14.88]
[Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 04/27/2018] [Indexed: 12/14/2022] Open
Abstract
Herein, we describe a catalytic fluorooxygenation of readily accessible N-allylcarboxamides via an I(I)/I(III) manifold to generate 2-oxazolines containing a fluoromethyl group. Catalysis is conditional on the oxidation competence of Selectfluor®, whilst HF serves as both a fluoride source and Brønsted acid activator. The C(sp3)-F bond of the mono-fluoromethyl unit and the C(sp3)-O bond of the ring are aligned in a synclinal relationship thereby engaging in stabilising hyperconjugative interactions with vicinal, electron-rich σ-bonds (σC-C→σ*C-F and σC-H→σ*C-O). This manifestation of the stereoelectronic gauche effect was established by X-ray crystallographic analysis of a representative example. Given the importance of fluorine in drug discovery, its ability to modulate conformation, and the prevalence of the 2-oxazoline scaffold in Nature, this strategy provides a rapid entry into an important bioisostere class.
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