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Stereoselectivity in (Acyloxy)borane-Catalyzed Mukaiyama Aldol Reactions

Författare och institution:
J. M. Lee (-); X. Zhang (-); Per-Ola Norrby (Institutionen för kemi och molekylärbiologi); P. Helquist (-); O. Wiest (-)
Publicerad i:
Journal of Organic Chemistry, 81 ( 13 ) s. 5314-5321
ISSN:
0022-3263
Publikationstyp:
Artikel, refereegranskad vetenskaplig
Publiceringsår:
2016
Språk:
engelska
Fulltextlänk:
Sammanfattning (abstract):
The origin of diastereo- and enantioselectivity in a Lewis acid catalyzed Mukaiyama aldol reaction is investigated using a combination of dispersion corrected DFT calculations and transition state force fields (TSFF) developed using the quantum guided molecular mechanics (Q2MM) method. The reaction proceeds via a closed transition structure involving a nontraditional hydrogen bond that is 3.3 kJ/mol lower in energy than the corresponding open transition structure. The correct prediction of the diastereoselectivity of a Mukaiyama aldol reaction catalyzed by the conformationally flexible Yamamoto chiral (acyloxy) borane (CAB) requires extensive conformational sampling at the transition structure, which is achieved using a Q2MM-derived TSFF, followed by DFT calculations of the low energy conformational clusters. Finally, a conceptual model for the rationalization of the observed diastereo-and enantioselectivity of the reaction using a closed transition state model is proposed.
Ämne (baseras på Högskoleverkets indelning av forskningsämnen):
NATURVETENSKAP ->
Kemi
Nyckelord:
diels-alder reactions, silyl ketene acetals, molecular-mechanics, force-field, conformational-analysis, reaction 40years, enol ethers, aldehydes, diastereoselectivity, catalyst, Chemistry
Postens nummer:
239848
Posten skapad:
2016-08-05 13:27

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