@article{22ab3c851e504119bedc31b2a20a8eb6,
title = "Enantioselective Protonation of Enol Esters with Bifunctional Phosphonium/Thiourea Catalysts",
abstract = "Bifunctional phosphonium/thioureas derived from tert-leucine behaved as highly selective catalysts for enantioselective protonation of enol esters, providing α-chiral ketones in yields of up to 99% with high enantioselectivities (up to 98.5:1.5 er). Control experiments clarified that a bulky tert-butyl group and phosphonium and thiourea moieties were necessary to achieve such high stereoselectivity. In addition, mechanistic investigations indicated the catalyst was converted to the corresponding betaine species, which served as a monomolecular catalyst.",
author = "Eiji Yamamoto and Kodai Wakafuji and Yusuke Mori and Gaku Teshima and Yuki Hidani and Makoto Tokunaga",
note = "Funding Information: This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI (Grant Nos. 16H07042 and 15K05431); a Grant-in-Aid for Scientific Research on Innovative Areas “Advanced Molecular Transformations by Organocatalysts” from The Ministry of Education, Culture, Sports, Science and Technology, Japan (No. 26105744); and the Research Program for Next Generation Young Scientists of “Five-star Alliance” in “NJRC Mater. & Dev.” We appreciate the reviewers for the fruitful suggestions in the peer review process. Publisher Copyright: Copyright {\textcopyright} 2019 American Chemical Society.",
year = "2019",
month = jun,
day = "7",
doi = "10.1021/acs.orglett.9b01216",
language = "English",
volume = "21",
pages = "4030--4034",
journal = "Organic letters",
issn = "1523-7060",
publisher = "American Chemical Society",
number = "11",
}