A variety of electrostatically enhanced 3-and 4pyridylborate salt catalysts are reported and show significant improvement over an activated noncharged neutral control compound. Their nucleophilicity in a stoichiometric S N 2 reaction and catalytic performance in a urethane synthesis are evaluated along with three methods for rapidly evaluating the basicity of these species. That is, qualitative titrations in CH 2 Cl 2 and CHCl 3 were carried out, two separate solution-state IR studies in CCl 4 and CDCl 3 are reported, and the proton affinities of the anionic components of the salts were computed. Charge differences between the anion and its protonated zwitterionic conjugate acid are evaluated along with the highest occupied molecular orbitals of the anions in relationship to some of the surprising reactivity findings that were observed in the two kinetic studies.

Several charge-containing TADDOL salts were synthesized and used as organocatalysts in asymmetric Diels-Alder and hetero-Diels-Alder reactions.Their catalytic activity was found to exceed that of a noncharged analog while maintaining or improving upon the enantioselectivity. The enhanced activities of the TADDOL salts enabled them to act as presumed hydrogen bond donor catalysts in the Diels-Alder and hetero-Diels-Alder reactions of 1,3-cyclohexadiene with methyl vinyl ketone at 40 C and 2-phenoxy-1,3-butadiene with ethyl glyoxylate at room temperature, respectively. Given the ionic nature of these charge-activated catalysts, it also proved possible to recycle and reuse the TADDOL without chromatography or the need for a recrystallization.

A series of ferrocenium (Fc, FcCO2H, FcCO2Me, and Fc­(Me)10) and cobaltocenium (Cc, CcCO2H, CcCO2Me) salts were prepared and explored as air- and water-tolerant homogeneous catalysts. They were found to be active catalysts at room temperature for the Friedel–Crafts alkylation of trans-β-nitrostyrene and N-methylindole and the Diels–Alder cycloaddition of 1,3-cyclohexadiene with methyl vinyl ketone. These catalysts are valuable additions to more traditional Lewis acids in that they are soluble in nonpolar media, did not decompose the starting materials, and dual activation exploiting both the Lewis (metal) and Brønsted acid (CO2H) centers was observed.

The tetramer of bis(4-di-n-butylaminophenyl)(pyridin-3-yl)borane [systematic name: 2λ4,4λ4,6λ4,8λ4-tetrabora-1,3,5,7(1,3)-tetrapyridinacyclooctaphane-11,31,51,71-tetrakis(ylium)], C132H192B4N12, was synthesized unexpectedly and crystallized. Its structure contains an unusual 16-membered ring core made up of four (pyridin-3-yl)borane groups. The ring adopts a conformation with pseudo-S 4 symmetry that is very different from the two other reported examples of this ring system. Density functional theory (DFT) computations indicate that the stability of the three reported ring conformations is dependent on the substituents on the B atoms, and that the pseudo-S 4 geometry observed in the bis(4-dibutylaminophenyl)(pyridin-3-yl)borane tetramer becomes significantly more stable when phenyl or 2,6-dimethylphenyl groups are attached to the boron centers.