Titanium-catalysed Miscellaneous Reactions

Besides the reactions described above, titanium-based complexes display both high catalytic activity and selectivity for a broad range of organic transformations, some of which are described below. 

The transformation of carbon-fluorine bonds into carbon-hydrogen bonds, known as hydrodefluorination reaction, is interesting for environmental chemists since it would help to remove fluorine-containing atmospheric 

Lentz and coworkers reported that air-stable titanocene difluoride can act as a catalyst for hydrodefluorination reactions in the presence of silane derivatives, giving excellent yields even at low temperature. The authors expanded the scope of the reaction to other substrates such as vinylic and allylic fluorides and a range of catalysts.Mechanistic studies indicated that a titanium(m) hydride is the active species, and the silane derivative is the hydride source. This catalytic system is not only interesting form the environmental point of view, but also for the synthesis of new organic molecules as it represents a new synthetic route to obtain inaccessible aminopyridine derivatives.  

Titanium tetrachloride has been studied in the hydrodefluorination reaction of trifluorotoluene derivatives in the presence of lithium aluminium hydride as hydride source, giving excellent yields. Rieger et al. studied group (iv) metallocenes dichlorides in carbon-fluorine activation reactions and they found higher catalytic activities for zirconocene and hafnocene complexes compared to the titanocene complex probably due to the tendency toward reduction of titanium(iv).  

Manners and coworkers described dehydrogenation of dimethylamine borane with titanocene complexes prepared in situ by reaction between the titanocene species and bulyllithium. The catalysts displayed good catalytic activity giving good yields.  

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