Intermolecular
C(sp3)–H insertions of β-carbonyl ester dirhodium-carbenes
are extremely rare. Toward developing efficient reactions of these
carbenes, a model for their insertion into C(sp3)–H
bonds is described using density functional theory (DFT) calculations.
In this study, the relevant electronic and steric components of β-carbonyl
ester dirhodium-carbenes that affect intermolecular C(sp3)–H activation energies are explored, parametrized, and used
to construct an intuitive model for predicting propensity for C–H
insertion. The resulting insights from the theoretical investigation
are actualized through experiments to establish reactivity trends
for these species and reaction discovery. On the basis of these integrated
computational and experimental efforts, examples of intermolecular
C(sp3)–H insertions featuring secondary α-diazo-β-amide
esters are reported. The resulting carbenes feature an intramolecular
1,6-hydrogen bond that affords increased stability and enhanced reactivity
for C(sp3)–H insertion as compared to other β-carbonyl
ester dirhodium-carbenes. The reactivity of these carbenes is also
highlighted through (1) an example of a cyclopropanation reaction
and (2) the use of a chiral dirhodium catalyst system.