Organozincs acidic-hydrogen

Water as the Co-)Solvent. In view of the reactivity of organozinc compounds towards acidic hydrogens, the use of water as the (co-)solvent in Zn-Barbier reactions is even more surprising than the use of alcohols. 

Ketones are less reactive than aldehydes toward organozinc reagents, and they are inherently less stereoselective because the differentiation is between two carbon substituents, rather than between a carbon substituent and hydrogen. Recently, a diol incorporating both franr-cyclohexanediamine and camphorsulfonic acid has proven effective in conjunction with titanium tetraisopropoxide.159... 

The organozinc prepared from propargyl bromide did not react with terminal alkynes because, under the reaction conditions, abstraction of the acidic terminal acetylenic hydrogen from the propargylic metabotropic form presumably occurred (equation 154)185. 

We have shown for the first time 12 that not only c/oso-carboranes, but also iodo-nido-7,8-dicarbaundecaborates containing an iodine atom in the polyhedral skeleton or in the pentagonal plane of the polyhedron enter into cross-coupling reactions with organomagnesium and organozinc compounds catalyzed by palladium complexes. It is known that ifo-7,8-dicarbaundecaborates are strong BH-acids (pKa = 21.1), due to the presence of the axial hydrogen atom. 

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