Mechanisms cross-dehydrogenative coupling

The same catalytic system as described for the CDC of amines and ni-troalkanes, complemented with C0CI2 as a co-catalyst, also proved efficient for the allylic alkylation via cross-dehydrogenative coupling between various cycloalkenes and diketones (Eq. 9). Again, the exact mechanism or role of the organic peroxide are not known to date, but the formation of water probably provides the thermodynamic driving force for these reactions [121,122]. 

By building their own vibration ball mill, Shayesteh and coworkers obtained 100% conversion in just 12 min at 30 Hz for cross-dehydrogenative coupling (CDC) of 2-naphthol [62]. In comparison, the Toda s mortar grinding and above described method by Rasmussen et al. needed 2 and 1 h, respectively. On operation condition of 30 Hz vibration ball mill gives better performance in comparison to other commonly used methods such as ball mill and mortar and pestle, due to higher mechanical... 

The cross-dehydrogenative coupling of N-protected acetanilides such as 112 with arenes proceeds with Pd(II) and Cu(II) via paUadacycles 113 (Scheme 11.38) [147]. Presumably, paUadacycles 113 react with the arenes by a proton-abstraction mechanism via transition state 114 to form Pd(II) complexes 115, which evolve by reductive elimination to yield the coupled products 116. A palladacycle was also involved in the related reaction of acetanilides with boronic acids catalyzed by Pd(ll) and Cu(ll) [148]. 

Scheme 14 A proposed reaction mechanism for the Ni-catalyzed cross-dehydrogenative coupling of C-H bonds with toluene C-H bonds...

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