Linear zinc compounds

The ligand 2,5-bis(2-pyridyl)pyrazine was used in the synthesis of a range of zinc compounds to contrast with copper coordination polymers prepared with this ligand.169 Three zinc compounds were structurally characterized, [ZnCl2L(DMF)], [Zn3(OAc)6L2], and [Zn3Cl6L3] respectively a distorted square planar monomer, a linear trimer, and a triangular arrangement of zinc centers. 

Table it.1-137 Linear thermal expansion coefficient a of zinc compounds... 

The total syntheses and SAR studies, notably by Ganesan with FK228 and Williams with largazole, have identified the key features within depsipeptide HDAC inhibitors that are required for HDAC inhibition (Figure 4.17). The macrocyclic backbone is essential as linear uncyclized compounds are inactive. Within the macrocycle, the zinc binding thiol warhead needs to be of D-stereochemistry and the epimer is virtually inactive, while the other amino acid residues present can be varied without loss in activity. The... 

The principal compounds in this category are the monochalacogenides, which are formed by all three metals. It is a notable indication of the stability of tetrahedral coordination for the elements of Group 12 that, of the 12 compounds of this type, only CdO, HgO and HgS adopt a structure other than wurtzite or zinc blende (both of which involve tetrahedral coordination of the cation — see below). CdO adopts the 6-coordinate rock-salt structure HgO features zigzag chains of almost linear O-Hg-0 units and HgS exists in both a zinc-blende form and in a rock-salt form. 

Allylic substitutions with nonstabilized C-nucleophiles are an important domain of organocopper chemistry [51]. However, on close inspection of the literature, it becomes apparent that regioselectivity in favor of the branched allylic alkylation products is only obtained with alkyl copper compounds, while aryl copper compounds mainly give the linear alkylation products. This observation was an incentive for Alexakis et al. [52] to probe the reactions of aryl zinc hahdes in the Ir-catalyzed allylic substitution (Scheme 9.18). 

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