Anion-Activated Bases and Nucleophiles Characterized by Photoelectron Spectroscopy.

Negative ion photoelectron spectra at 20 K along with ab initio [CCSD(T)] and M06-2X density functional theory calculations are reported for a series of six basic and nucleophilic pyridine derivatives with an anionic substituent [i.e., 3- and 4-PyrBX, where X = F, 4--BuCH, 4-MeOCH, and 3,5-(MeO)CH].

Electrostatically Enhanced 3- and 4-Pyridyl Borate Salt Nucleophiles and Bases.

A variety of electrostatically enhanced 3- and 4-pyridylborate salt catalysts are reported and show significant improvement over an activated noncharged neutral control compound. Their nucleophilicity in a stoichiometric S2 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 CHCl and CHCl were carried out, two separate solution-state IR studies in CCl and CDCl are reported, and the proton affinities of the anionic components of the salts were computed.

Structure determination of a bis[4-(di-n-butylamino)phenyl](pyridin-3-yl)borane tetramer highlighting a unique geometric conformation of the core 16-membered ring.

The tetramer of bis(4-di-n-butylaminophenyl)(pyridin-3-yl)borane [systematic name: 2λ,4λ,6λ,8λ-tetrabora-1,3,5,7(1,3)-tetrapyridinacyclooctaphane-1,3,5,7-tetrakis(ylium)], CHBN, 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 symmetry that is very different from the two other reported examples of this ring system.

Liberating the Anion: Evaluating Weakly Coordinating Cations.

A series of commonly used weakly coordinating cations (WCCs) including tetraalkylammonium, bis(triphenylphosphine)iminium (PPN), P2 and P5 phosphazenium, and tetraphenylphosphonium ions were investigated along with five additional tetraarylphosphonium ions [Ar = 4-Me, 4--Bu, 3,5-Me, 4-MeN, and 3,5-(MeO) phenyl derivatives]. Dissociation enthalpies of their chloride complexes were computed in the gas phase and in dichloromethane. These results are compared to infrared spectra of these salts in chloroform- which provide free and bound C-D stretches, F NMR spectra of the corresponding tetrafluoroborate salts, ion-pair equilibrium constants, and reaction rates of the chlorides and acetates with 1-iodooctane.

Facile syntheses of functionalized toll-like receptor 7 agonists.

Protein conjugates of toll-like receptor 7 agonists have been shown to elicit powerful immune responses. In order to facilitate our studies in this area our group has developed efficient syntheses for a number of functionalized derivatives that retain immune stimulatory activity.