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(C(6)F(5))(3)-catalysed transfer reactions of El–H to π- and σ-donors (C[double bond, length as m-dash]C/C[triple bond, length as m-dash]C and C[double bond, length as m-dash]O/C[double bond, length as m-dash]N). 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.