Dirhodium(II) tetrakis[ N-tetrafluorophthaloyl-( S)- tert-leucinate]: an exceptionally effective Rh(II) catalyst for enantiotopically selective aromatic C–H insertions of diazo ketoesters

Abstract

Dirhodium(II) tetrakis[ N-tetrafluorophthaloyl-( S)- tert-leucinate], Rh 2[( S)-TFPTTL] 4, in which the phthalimido hydrogen atoms of the parent dirhodium(II) complex are substituted by fluorine atoms, dramatically enhances the reactivity and enantioselectivity (up to 97% ee) in intramolecular aromatic C–H insertion reactions of methyl 4-alkyl-2-diazo-4,4-diphenyl-3-oxopropionates. Catalysis with the use of 0.001 mol% of Rh 2[( S)-TFPTTL] 4 has achieved the highest turnover number (up to 98,000 with the methyl substituent) ever recorded for chiral dirhodium(II) complex-catalyzed carbene transformations, without compromising the yield or enantioselectivity of the process.