Diruthenium Tetracarboxylate-Catalyzed Enantioselective Cyclopropanation with Aryldiazoacetates

A series of chiral bowl-shaped diruthenium(II,III) tetracarboxylate catalysts were prepared and evaluated in asymmetric cyclopropanations with donor/acceptor carbenes derived from aryldiazoacetates. The diruthenium self-assembled to generate C4-symmetric structures an analogous manner their dirhodium counterparts. optimum catalyst was found be Ru2(S-TPPTTL)4·BArF [S-TPPTTL = (S)-2-(1,3-dioxo-4,5,6,7-tetraphenylisoindolin-2-yl)-3,3-dimethylbutanoate, BArF tetrakis(3,5-bis(trifluoromethyl)phenyl)borate], which resulted the cyclopropanation a range substrates up 94% ee. Synthesis evaluation first-row transition-metal congeners [Cu(II/II) Co(II/II)] invariably that afforded little no induction. Computational studies indicate carbene complexes these dicopper dicobalt complexes, unlike systems, are prone loss carboxylate ligands, would destroy structure critical for