Light-Induced Enantiospecific 4蟺 Ring Closure of Axially Chiral 2-Pyridones: Enthalpic and Entropic Effects Promoted by H-Bonding

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• 作者：Elango Kumarasamy ; Josepha L. Jesuraj ; Joseph N. Omlid ; Angel Ugrinov ; Jayaraman Sivaguru
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：November 2, 2011
• 年：2011
• 卷：133
• 期：43
• 页码：17106-17109
• 全文大小：833K
• 年卷期：v.133,no.43(November 2, 2011)
• ISSN：1520-5126

文摘

Nonbiaryl axially chiral 2-pyridones were synthesized and employed for light-induced electrocyclic 4蟺 ring closure leading to bicyclo-尾-lactam photoproducts in solution. The enantioselectivity in the photoproducts varied from 22 to 95% depending on the reaction temperature and the ability of the axially chiral chromophore to form intramolecular and/or intermolecular H-bonds with the solvent. On the basis of the differential activation parameters, entropic control of the enantiospecificity was observed for 2-pyridones lacking the ability to form H-bonds. Conversely, enthalpy played a significant role for 2-pyridones having the ability to form H-bonds.