Stereospecific palladium(0)-catalyzed reduction of 2-cyclobutylidenepropyl esters: A versatile preparation of diastereomeric monoterpenoids: (±)-Fragranol and (±)-Grandisol

Mixture of (E and Z)-2-cyclobutylidenepropyl sulfonates, readily available from alfa,alfa-disubstituted cyclobutanes arising from suitable cyclopropane derivatives ring expansion, underwent regioselective and stereospecific reduction by formate anion to offer, through pi-greco 1,1-trimethyleneallylpalladium complexes formed upon treatment with palladium(0), a new and convenient entry to the diastereomeric four-membered ring monoterpenoids racemica fragranol and racemic grandisol.