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Asymmetric Synthesis of Adjacent Tri- and Tetrasubstituted Carbon Stereocenters. Organocatalytic Aldol Reaction of an Hydantoin Surrogate with Azaarene 2-Carbaldehydes.

Autoría:
J. Izquierdo, N. Demurget, A. Landa, T. Brinck, J. M. Mercero, P. Dinér, M. Oiarbide, C. Palomo
Año:
2019
Revista:
Chem. Eur. J.
Factor de impacto:
5.160
Cuartil:
Q1
Volumen:
25
Página de inicio - Página de fin:
12431 - 12438
ISBN/ISSN:
ISSN: 1521-3765 (web)
DOI:
10.1002/chem.201902817
Descripción:

Abstract: 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.upto>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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