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Pure Appl. Chem., 2006, Vol. 78, No. 2, pp. 463-467

Catalytic asymmetric ring-opening of cyclopentadiene - heterodienophile cycloadducts with organometallic reagents

Mauro Pineschi, Federica Del Moro, Paolo Crotti and Franco Macchia

Dipartimento di Chimica Bioorganica e Biofarmacia, Università di Pisa, Via Bonanno 33, 56126, Pisa, Italy

Abstract: An unprecedented catalytic asymmetric ring-opening of easily accessible 2,3-heterosubstituted norbornenes with hard alkyl metals (R-M), is able to give a practical regio- and stereoselective access to hetero-functionalized alkyl cyclopentenes in an enantioenriched form. The copper-catalyzed desymmetrization reaction with trialkylaluminums of sterically hindered and rigid, tri- or tetracyclic Diels-Alder adducts, easily available by cycloaddition reaction of cyclopentadiene with 4-phenyl-urazole and 2,3-phthalazine-1,4-dione, proved to be particularly efficient. Interestingly, the chirality of the amine part of the BINOL-based phosphoramidite is able to impose the absolute stereochemistry of the corresponding adducts.