Atomic Born radii (α) are used in the generalized Born (GB) equation to calculate approximations to the electrical polarization component (G pol) of solvation free energy. We present here a simple analytical formula for calculating Born radii rapidly and with useful accuracy. The new function is based on an atomic pairwise r ij -4 treatment and contains several empirically determined parameters that were established by optimization against a data set of >10 000 accurate Born radii computed numerically using the Poisson equation on a diverse group of organic molecules, molecular complexes, oligopeptides, and a small protein. Coupling this new Born radius calculation with the previously described GB/SA solvation treatment provides a fully analytical solvation model that is computationally efficient in comparison with traditional molecular solvent models and also affords first and second derivatives. Tests with the GB/SA model and Born radii calculated with our new analytical function and with the accurate but more time-consuming Poisson−Boltzmann methods indicate that comparable free energies of solventlike dielectric polarization can be obtained using either method and that the resulting GB/SA solvation free energies compare well with the experimental results on small molecules in water.

Transition-metal-catalyzed cross-coupling reactions have been well-established as indispensable tools in modern organic synthesis. One of the major research goals in cross-coupling area is expanding the scope of the coupling partners. In the past decade, diazo compounds (or their precursors N-tosylhydrazones) have emerged as nucleophilic cross-coupling partners in C-C single bond or C═C double bond formations in transition-metal-catalyzed reactions. This type of coupling reaction involves the following general steps. First, the organometallic species is generated by various processes, including oxidative addition, transmetalation, cyclization, C-C bond cleavage, and C-H bond activation. Subsequently, the organometallic species reacts with the diazo substrate to generate metal carbene intermediate, which undergoes rapid migratory insertion to form a C-C bond. The new organometallic species generated from migratory insertion may undergo various transformations. This type of carbene-based coupling has proven to be general: various transition metals including Pd, Cu, Rh, Ni, Co, and Ir are effective catalysts; the scope of the reaction has also been extended to substrates other than diazo compounds; and various cascade processes have also been devised based on the carbene migratory insertion. This review will summarize the achievements made in this field since 2001.

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Lewis base adducts of tetra-alkoxy diboron compounds, in particular bis(pinacolato)diboron (B2 pin2 ), have been proposed as the active source of nucleophilic boryl species in metal-free borylation reactions. We report the isolation and detailed structural characterization (by solid-state and solution NMR spectroscopy and X-ray crystallography) of a series of anionic adducts of B2 pin2 with hard Lewis bases, such as alkoxides and fluoride. The study was extended to alternative Lewis bases, such as acetate, and other diboron reagents. The B(sp(2) )-B(sp(3) ) adducts exhibit two distinct boron environments in the solid-state and solution NMR spectra, except for [(4-tBuC6 H4 O)B2 pin2 ](-) , which shows rapid site exchange in solution. DFT calculations were performed to analyze the stability of the adducts with respect to dissociation. Stoichiometric reaction of the isolated adducts with two representative series of organic electrophiles-namely, aryl halides and diazonium salts-demonstrate the relative reactivities of the anionic diboron compounds as nucleophilic boryl anion sources.

Aryl diazonium salts are versatile building blocks in organic synthesis. In light of the ever-increasing importance of aryl diazonium salts spanning most disciplines of the chemical sciences, we review the recent development of aryl diazonium chemistry over the past seven years (2013−2020). Special emphasis is put on various new transformations involving the generation of radical intermediates via thermal, photochemical, and electrochemical means. Recent advances in the development of transition metal-catalyzed reactions using aryl diazonium salts are also reviewed. Together, these newly developed transformations significantly expand the synthetic chemist's repertoire of aromatic carbon−carbon and carbon−heteroatom bond forming methods using aryl diazonium precursors, providing powerful tools for the synthesis and modification of complex molecular scaffolds.

Leave the metal out: Arylboronates are produced in moderate to good yields by direct borylation of readily available aryl amines (see scheme). The reaction can be carried out under air at room temperature and transition‐metal catalysis is not required. The boronate products can be used without purification in Suzuki–Miyaura cross‐coupling reactions.

A novel strategy for aromatic trifluoromethylation by converting aromatic amino group into CF3 group is reported herein. This method, which can be considered as trifluoromethylation variation of the classic Sandmeyer reaction, uses readily available aromatic amines as starting materials and is performed under mild conditions.

The resonance Raman (RR) spectra of blue copper proteins are unusually complicated, with at least five bands in the 400-cm-l region. To explore the sources of this complexity we have examined RR spectra of LCuSR complexes [L = hydrotris(3,5-diisopropyl-l-pyrazolyl)borate], which are known to be close structural and electronic analogs of the blue Cu site. When the C atom which is attached to the S atom lacks a proton, a single prominent band is seen near 430 cm-l, assignable to the stretching mode of a short (ca. 2.1 A) C u S bond, which is characteristic of the blue Cu site, and of the model complexes. The frequency decreases in the order R = tert-butyl > triphenylmethyl > pentafluorophenyl, consistent with the expected effect of increasing electron withdrawal on the C u S bond strength.Weaker bands are seen at lower frequencies, which are attributed to thiolate internal bending and to Cu-N[pyrazole] stretching coordinates. These assignments were confirmed with a normal coordinate analysis for the tert-butylthiolate complex, which accurately reproduced the frequencies and isotope shifts for perdeuteration of the tert-butyl substituent. When R = sec-butyl, three prominent bands are seen in the 400-cm-l region instead of one. Normal mode analysis shows extensive mixing of C u S stretching with C -C S and C-C-C bending coordinates in these three modes, occasioned by the inequivalences in the bending coordinates and the involvement of HC-CH torsion. Implications for the blue copper protein RR spectra are discussed.