Studies on A Novel Asymmetric Cycloaddition Using Optically Active <alpha> , <beta> -Unsaturated Sulfoxides

研究了取代芳基亚磺酰基乙烯（乙烯基亚砜）的不对称Diels-Alder反应。高的非对映选择性被解释为在能量上有利的s-顺式或s-反式构象异构体中从硫孤对侧的二烯途径的有利方向，并且乙烯基亚砜中的构象偏好基于S-O与或位置处的取代基之间的偶极-偶极和/或空间相互作用而合理化<alpha><beta>。使用2-吡啶基亚磺酰基代替对甲苯基亚磺酰基显著提高了反应活性，并且通过与呋喃的环加成反应得到7-氧杂双环[2.2.1]庚-5-烯-2-羧酸衍生物，也保持了高的非对映选择性。实现了不对称Diels-Alder反应在手性合成某些具有生物活性的天然产物中的应用。

Asymmetric Diels-Alder reaction using substituted arylsulfinylethenes (vinyl sulfoxides) has been studied. The high diastereoselectivity was interpreted in terms of the favored direction of the diene approach from the side of the sulfur lone pair in energetically favored s-cis or s-trans conformers and the conformational preferences in vinyl sulfoxides are rationalized on the basis of dipole-dipole and/or steric interactions between S-O and the substituents at <alpha> or <beta> position.On the otherhand, the use of 2-pyridylsulfinyl group in place of p-tolyl-sulfinyl group enhanced the reactivity considerably and the high diastereoselectivity was also maintained by the cycloaddition with furan to give 7-oxabicyclo [2.2.1]hept-5-ene-2-carboxylic acid derivatives. The application of the asymmetric Diels-Alder reaction to the chiral synthesis of some biologically active natural products was achieved.