Rhodium-Catalyzed Carbonylation of Cyclopropyl Substituted Propargyl Esters: A Tandem 1,3-Acyloxy Migration [5 + 1] Cycloaddition

We have developed two different types of tandem reactions
for the
synthesis of highly functionalized cyclohexenones from cyclopropyl
substituted propargyl esters. Both reactions were initiated by rhodium-catalyzed
Saucy–Marbet 1,3-acyloxy migration. The resulting cyclopropyl
substituted allenes derived from acyloxy migration then underwent
[5 + 1] cycloaddition with CO. The acyloxy group not only eased the
access to allene intermediates but also provided a handle for further
selective functionalizations.