Chiral phosphite-urea bifunctional catalysts have been developed for the enantioselective bromocyclization of 2-geranylphenols with N-bromophthalimide (NBP) for the first time. The chiral triaryl phosphite moiety activates NBP to generate a bromophosphonium ion. On the other hand, the urea moiety interacts with a hydroxyl group of the substrate through hydrogen bonding interactions. Enantioselectivity is effectively induced through two-point attractive interactions between the catalyst and the substrate.
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http://dx.doi.org/10.1039/c6cc00229c | DOI Listing |
Chemistry
February 2024
Institute for Catalysis, Hokkaido University, Sapporo, Hokkaido, 001-0021, Japan.
Scavengers that capture reactive chemical substances are used to prevent the decomposition of materials. However, in the field of catalysis, the development of scavengers that inhibit background pathways has attracted little attention, although the concept will open up an otherwise inaccessible reaction space. In catalytic bromination, fast non-catalyzed background reactions disturb the catalytic control of the selectivity, even when using N-bromoamide reagents, which have a milder reactivity than bromine (Br ).
View Article and Find Full Text PDFChem Asian J
April 2023
School of Pharmaceutical Sciences, University of Shizuoka, Suruga-ku, Shizuoka, 422-8526, Japan.
We describe regio- and enantioselective bromocyclization of difluoroalkenes catalyzed by chiral bisphosphine oxides. Owing to the simultaneous activation of both the brominating reagent and amide substrate, the desired cyclization reaction proceeds smoothly even at low temperature to provide bromodifluoromethyl-containing oxazolines with a chiral quaternary center in a highly enantioselective fashion (up to 99% ee). This protocol features the use of commercially available brominating reagents and readily accessible chiral catalysts.
View Article and Find Full Text PDFJ Am Chem Soc
May 2020
Department of Chemistry, University of California, Berkeley, California 94720, United States.
Difluoromethylene-containing compounds have attracted substantial research interest over the past decades for their ability to mimic biological functions of traditional functional groups while providing a wide variety of pharmacological benefits bestowed by the C-F bond. We report a novel strategy to access RCFBr-containing heterocycles by regio- and enantioselective bromocyclization of difluoroalkenes enabled by chiral anion phase-transfer catalysis. The utility of this methodology was highlighted through a synthesis of an analogue of efavirenz, a drug used for treating HIV.
View Article and Find Full Text PDFChemistry
December 2018
Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya, Aichi, 468-8503, Japan.
J Am Chem Soc
August 2018
Institute of Chemistry and Biochemistry , Freie Universität Berlin, Takustraße 3 , 14195 Berlin , Germany.
We report a chiral phosphoric acid catalyzed bromocyclization/regiodivergent reaction of racemic intermediates sequence, which is enabled by anchimeric oxygen borrowing. Different types of alkenes are applicable, and both enantiomers of the bromohydrin products were obtained in generally excellent yields and enantioselectivities. In addition, an example of enantioconvergent synthesis from the two isomeric products is presented.
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