N-Phenylsulfonyl (S)-proline catalyzes the direct aldol reaction of 3-substituted cyclobutanones and aryl aldehydes in good yield and with excellent diastereoselectivity and enantioselectivity. This desymmetrization process provides highly functionalized cyclobutanones with control over three contiguous stereogenic centers.

[reactions: see text] Regioselective synthesis of 2,4,5- or 3,4,5-trisubstituted 2,3-dihydrofurans has been realized by using donor-acceptor cyclopropanes or by a Corey ylide reaction with alpha-sulfenyl-, alpha-sulfinyl-, or alpha-sulfonylenones. The method allowed a straightforward synthesis of the natural product calyxolane B.

An overview of the most important synthetic strategies currently available for the preparation of cyclopent-2-enones is presented and illustrated with recent applications.

An eco-friendly methodology for the direct alpha-sulfanylation of ketones, has been developed. The procedure, based on the use of functionalized diaryldisulfides and catalyzed by D,L-proline, represents a mild and efficient approach for the preparation of alpha-arylthio-ketones