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

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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.