Efficient Syntheses of Highly Substituted Organic Molecules Starting from Torquoselective Olefination

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We have developed the highly stereoselective olefination of carbonyl compounds with ynolates, and clarified the reaction mechanism by the theoretical calculations and the generality. The olefination of alkynyl ketones via ynolates provided the corresponding en-yne compounds with high E-selectivity, in which the alkynyl group works as an electron donating group in the torquoselectivity. The resulting olefins were converted into β-alkoxy divinyl ketones, which was subjected to the catalytic Nazarov reaction to afford α-alkoxy cyclopentenones in good yield. This cyclization was applied to the synthetic study of stemona alkaloids.