Royal Society of Chemistry, Chemical Communications, 77(52), p. 11575-11578
DOI: 10.1039/c6cc05838h
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A diastereoselective, DABCO-catalyzed reaction of isatin-derived ketimines with allenoates is described. Exploiting the stereodirecting effect of the bulky tert-butanesulfinyl chiral auxiliary, the method provides an efficient access to single diastereoisomers of unprecedented spirocyclic oxindoles, bearing a 4-methyleneazetidine ring at the spiro junction. The versatility of the method is fully demonstrated by further transformations including the conversion to relevant spirocyclic oxindolo-[small beta]-lactams.