Selectivity of C-H activation Carbon–hydrogen bond activation

in figure above, axial c-h bond in cis-1,2-dimethylcyclohexane selectively oxidized on equatorial c-h bond. during oxidation, axial methyl group becomes planar, decreasing 1,3-diaxial interactions in transition state, stabilizes transition state.

an alkene c–h bond activation rhodium catalyst demonstrated in synthesis of strained bicyclic enamine:

^ du, x.; houk, k. n. (1998). transition states alkane oxidations dioxiranes . j. org. chem. 63: 6480–6483. doi:10.1021/jo9801519. 
^ yotphan, sirilata; bergman, robert g.; ellman, jonathan a. stereoselective formation of bicyclic enamines bridgehead unsaturation via tandem c–h bond activation/alkenylation/ electrocyclization j. am. chem. soc. . 2008 . 130: 2452–2453. doi:10.1021/ja710981b.