C-H functionalizations by means of direct borane-hydrocarbon dehydrogenations and dehydrocarbonations.

The C-H functionalization of methane by means of direct C--H borations with BH(3) or MeBH(2) is compared computationally (using the B3LYP/6-311(++)G** method) to C-H lithiations with LiH or LiMe as well as to other analogue C-metal (Be, Na, Mg, Al) formations. For the borations only, this internal electrophilic substitution at carbon (S(E)i) relies more on the electrophilicity of boron than on the basicity of the internal base Y, that is, H or Me. Such direct borations of methane are more favored for dehydrogenations than for dehydrocarbonations. Due to decreased electrophilicity, substituents at boron disfavor such borations. Hence, the BH(2) group appears to be most efficient for C--H functionalizations by means of direct hydrocarbon borations.