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DOI: 10.1055/sos-SD-026-00397

Salaün, J.Science of Synthesis, (200526571.

Cyclobutanones can also be prepared by [2+2] cycloadditions in which thioacetals are used with chiral catalysts to give products with significant asymmetric induction. For example, cyclobutanone thioacetal 70 is obtained in 89% yield and >90% ee when the [2+2] cycloaddition of ketene dimethyl dithioacetal with but-2-enoate 68 is catalyzed by the chiral titanium reagent obtained in situ from dichlorodiisopropoxytitanium(IV) and chiral diol 69 (Scheme 28).[‌68‌] Thioacetal 70 is readily converted into chiral cyclobutan­ones.

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