179. Stereocontrolled Syntheses of Polysubstituted 2,3-Dihydro-4H-pyran-4-ones by cyclocondensation of β-acyloxy-ketones
     Oppolzer, W.; Rodriguez, I.
     Helv. Chim. Acta 1993, 76, 1282-1291

syn-β-Acyloxy-ketones 6 and an anti-β-acyloxy-ketone 17 undergo smooth intramolecular enolate/ester condensations 6 18 and 17 19 when treated with TiCl₄/EtN(i-Pr)₂. Thus, tri- and tetrasubstituted cis- or trans-2,3-dihydro-4H-pyran-4-ones are easily prepared in a stereoselective manner.

DOI : 10.1002/hlca.19930760315 

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