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

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.