Enantioselective Vinylogous Michael Organocascade of COCF3-Tethered Enediones and Pyrazolinones: Access to Spiro-Fused Linear Oxa-Triquinanes

We report a streamlined organocatalytic enantioselective construction of spiro-fused polycyclic scaffolds, achieving excellent yields and diastereo- and enantioselectivities. A bifunctional squaramide catalyst enables an asymmetric VMA reaction, followed by a proton transfer/aldol/acetalization cascade of vinylogous pyrazolones with trifluoroacetyl-tethered enediones. Additionally, the scalability and postsynthetic transformations of the titled products highlight their synthetic utility. Furthermore, control experiments confirmed the stability of the cyclic hemiketals present in the oxa-triquinanes.