期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 25, 期 53, 页码 12431-12438出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201902817
关键词
asymmetric catalysis; azaarenes; Bronsted bases; hydantoins; quaternary stereocenters
资金
- University of the Basque Country UPV/EHU [UFI QOSYC 11/22]
- Basque Government [IT-1236-19]
- Ministerio de Economia y Competitividad (MEC), Spain [CTQ2016-78487-C2]
- KTH-Royal Institute of Technology
A bifunctional amine/squaramide catalyst promoted direct aldol addition of an hydantoin surrogate to pyridine 2-carbaldehyde N-oxides to afford adducts bearing two vicinal tertiary/quaternary carbons in high diastereo- and enantioselectivity (d.r. up to >20:1; ee up to 98 %) is reported. Acid hydrolysis of adducts followed by reduction of the N-oxide group yields enantiopure carbinol-tethered quaternary hydantoin-azaarene conjugates with densely functionalized skeletons. DFT studies of the potential energy surface (B3LYP/6-31+G(d)+CPCM (dichloromethane)) of the reaction correlate the activity of different catalysts and support an intramolecular hydrogen-bond-assisted activation of the squaramide moiety in the transition state of the catalytic reaction.
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