Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, USA.
J Am Chem Soc. 2011 Nov 2;133(43):17106-9. doi: 10.1021/ja203087a. Epub 2011 Oct 7.
Nonbiaryl axially chiral 2-pyridones were synthesized and employed for light-induced electrocyclic 4π ring closure leading to bicyclo-β-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.
非联芳轴向手性 2-吡啶酮被合成，并用于光诱导的电环化 4π 环闭合，在溶液中生成双环-β-内酰胺光产物。光产物的对映选择性取决于反应温度和轴向手性生色团与溶剂形成分子内和/或分子间氢键的能力，范围从 22%到 95%不等。根据差分活化参数，观察到缺乏形成氢键能力的 2-吡啶酮的对映选择性受到熵控制。相反，对于具有形成氢键能力的 2-吡啶酮，焓起着重要作用。
