Stereoselective ring opening of meso bicyclic hydrazines: a straightforward approach to hydrazino cyclopentenic cores.

The diastereoselective synthesis of hydrazinocyclopentenes 6 or 7 can be achieved in a straightforward manner from Diels-Alder adduct 4 using an acid-catalyzed rearrangement or a palladium-catalyzed allylic substitution reaction. In the latter case, enantioenriched compounds with ee values up to 58% can be obtained when an appropriate chiral ligand is used. [reaction: see text]

Reversal of enantioselectivity in the asymmetric rhodium- versus iridium-catalyzed hydroboration of meso substrates.

The Ir-catalyzed asymmetric hydroboration of bicyclic hydrazines with ee and chemical yields up to 64% is reported. The switch from rhodium to iridium leads systematically to opposite enantiomers in this desymmetrization reaction.