ENANTIOSELECTIVE SYNTHESIS OF FUNCTIONALIZED TROPANES BY RHODIUM(II) CARBOXYLATE-CATALYZED DECOMPOSITION OF VINYLDIAZOMETHANES IN THE PRESENCE OF PYRROLES

A series of enantiomerically enriched tropanes was synthesized by the rhodium(II) octanoate-catalyzed reaction of various N-BOC-protected py rroles with vinyldiazomethanes. The overall 3 + 4 annulation occurs by a tandem cyclopropanation/Cope rearrangement. Asymmetric induction wa s best achieved in these transformations by using either (S)-lactate o r (R)-pantolactone as a chiral auxiliary on the vinyldiazomethanes. Re actions carried out with the chiral catalyst tetrakis[N-( tert-butylbe nzenesulfonyl)-(L)-prolinato]dirhodium (2) provided moderate asymmetri c induction, but also resulted in the formation of isomeric azabicyclo octane side products. The utility of the synthetic process was demonst rated through the asymmetric synthesis of(-)-anhydroecgonine methyl es ter and (-)-ferruginine.