Photoacetylation of Diamondoids: Selectivities and Mechanism (Eur. J. Org. Chem. 30/2009)

The cover picture shows shows the photochemical generation of triplet diacetyl (butadione, center) and its highly selective C–HH bond-activation reactions in the functionalizations of tertiary C–H bonds. Despite several similarly reactive tertiary C–HH bonds and a multitude of secondary C–HH bonds with similar or even smaller bond dissociation energies (blue hydrogen atoms on structures on the left), this reagent shows remarkable selectivity for the apical positions of diamondoids owing to its high sensitivity to steric hindrance. This gives the respective apical acetyl diamondoids (blue groups on the right) in high yields. Deuterium kinetic isotope effects and accompanying computational studies shed light on the rate-determining C–HH bond-activation step. Details are discussed in the article by A. A. Fokin, P. R. Schreiner et al. on p. 5153 ff.