A New Base For Selective Deprotonation of Weak CH Acids

Organolithium and organomagnesium compounds are often kinetically poor bases for proton removal from weak carbon acids. LDA can be effective for pKa in the 30-35 range, but the liberated amine may have a similar pKa and it is difficult to drive reactions to completion.

A new base formed by adding anhydrous isopropylamine to dibutylmagnesium is effective at deprotonation, and reactions are driven to competion by irreversible formation of butane (Zhang M X et al, Angew Chem Int Ed, 2002, 41, 2169). The methodology has been used to alkylate and arylate cyclopropanes and cyclobutanes.