Nucleophilic susceptibility

By exploiting electrostatic field effects (unfavourable through-space charge-dipole repulsion) to increase the nucleophilic susceptibility of cyclohexanones, more efficient catalysts (16) and (17) for epoxidafion through in situ dioxirane formation have been designed. ... 

A type of mixed anhydride derivative (2, see p. 322) has been produced by reaction of O-(carboxymethyl) cellulose with ethyl chloro-formate, and is useful in insolubilization of macromolecules because of its nucleophilic susceptibility. ... 

Acylation catalysts, typically nucleophilic amines and imines that activate caiboxylates by forming highly nucleophile-susceptible acyliminium intermediates, promote a wide variety of synthetically useful caiboxylate transformations. Many are sufiSciently water-soluble to evaluate as anhydride hydrolysis catalysts. Scheme 1 depicts a representative example of this class of reaction, the hydrolysis of a P(NB/MA) polymer matrix in aqueous base (TMAH) catalyzed by 4-(dimethylamino)pyridine (DMAP). 

Electron density surface of the bro-monium ion from isobutene, shaded by nucleophilic susceptibility. 

Figure 9.16 shows a portion of the PM3 electron density surface of the bromonium ion derived from isobutene. The C-CH2—Br bond angle was fixed at 80° in accordance with the results reported in reference 77. The shading illustrates regions of similar nucleophilic susceptibility, which was calculated on the basis of the density of frontier MOs by the method of Fukui et al. The nucleophilic susceptibility on the carbon atom with the two hydrogen atoms is 0.04, while that for the carbon atom with two methyl substituents is 1.18. Therefore, an incoming nucleophile would be attracted more strongly to the more substituted carbon atom of the bromonium ion. ... 

By comparison, nucleophilic susceptibility was found to be 0.46 for each of the two carbon atoms in the bromonium ion formed from ethene. These results are consistent with the tendency for the bromonium ion from isobutene to react with nucleophiles at the more highly substituted position, but the calculated structures implicitly represent gas phase species. Structures in solution may be affected by solvent or counterions. 

Figure 4 Electron density isosurface (cut open for visibility), color coded by nucleophilic susceptibility for acyclovir , shown as a ball-and-stick model...

---