Cyclohexa-1,4-dienes in transition-metal-free ionic transfer processes
Safe- and convenient-to-handle surrogates of hazardous chemicals are always in demand. Recently introduced cyclohexa-1,4-dienes with adequate substitution fulfil this role as El+/H− equivalents in B(C6F5)3-catalysed transfer reactions of El–H to π- and σ-donors (CC/CC and CO/CN). Surrogates of Si–H/Ge–H, H–H and even C–H bonds have been designed and successfully applied to ionic transfer hydrosilylation/hydrogermylation, hydrogenation and hydro-tert-butylation, respectively. These processes and their basic principles are summarised in this Minireview. The similarities and differences between these transfer reactions as well as the challenges associated with these transformations are discussed.