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

Mixtures of (E and Z)-2-cyclobutylidenepropyl sulfonates, readily available from alpha,alpha-disubstituted cyclobutanones arising from suitable cyclopropane derivatives ring expansion, underwent regioselective and stereospecific reduction by formate anion to offer, through pi-1, 1-trimethyleneallylpalladium complexes formed upon treatment with palladium(O), a new and convenient entry to the diastereomeric four-membered ring monoterpenoids (+/-)-fragranol and (+/-)-grandisol. (C) 2003 Elsevier Ltd. All rights reserved.