Very high stereoselectivity in organocatalyzed desymmetrizing aldol reactions of 3-substituted cyclobutanonesElectronic supplementary information (ESI) available: Experimental procedures, copies of NMR spectra, HPLC analyses, X-ray diffraction data. CCDC reference numbers 752280 and 796934. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2ob25813g

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. N -Phenylsulfonyl ( S )-proline catalyzes the direct aldol reaction of 3-substituted cyclobutanones and aryl aldehydes with excellent diastereoselectivity and enantioselectivity.