Silver(I) complexes of 6-methyl-2-pyridinecarboxylic acid: the crystal structure of [Ag(MeC5H3NCOO)(MeC5H3NCOOH)]

Silver(I) complexes of 6-methyl-2-pyridinecarboxylic acid (HL) have been prepared, and the crystal structure of [Ag(L)(LH)] has been determined from X-ray diffraction data. This complex crystallizes in the monoclinic space group P2₁/n, with a = 13.4055(13), b = 7.1012(7), c = 15.588(2) Å, = 112.779(2)°, and Z = 4. Anionic [AgL₂]^– units are linked together by protons in approximately symmetrical linear O—H—O hydrogen bonds involving uncoordinated carboxylate oxygen atoms, to give polymeric chains. The most significant intermolecular interaction between adjacent parallel chains is offset ring stacking of pairs of aromatic rings with a perpendicular distance of 3.27 Å. The Ag coordination geometry is highly distorted tetrahedral, from two pyridine N atoms and two carboxylate O atoms, each ligand forming a five-membered chelate ring.     

Fractional eigenvalues

We study the non-local eigenvalue problem $$\begin{aligned} 2\, \int \limits _{\mathbb{R }^n}\frac{|u(y)-u(x)|^{p-2}\bigl (u(y)-u(x)\bigr )}{|y-x|^{\alpha p}}\,dy +\lambda |u(x)|^{p-2}u(x)=0 \end{aligned}$$ for large values of $p$ and derive the limit equation as $p\rightarrow \infty $ . Its viscosity solutions have many interesting properties and the eigenvalues exhibit a strange behaviour.     

Frustrated Lewis Pair Chemistry of Chiral (+)‐Camphor‐Based Aminoboranes

Dimethylamino‐(+)‐camphorenamine reacted with an equimolar amount of Piers’ borane, HB(C₆F₅)₂, to give the corresponding iminium–hydroborate zwitterionic salt. Being in equilibrium with the parent enamine–HB(C₆F₅)₂ N–B pair, this salt was able to split hydrogen heterolytically, hydrogenating the iminium group in the molecule. Detailed studies revealed that the hydrogen splitting in this reaction proceeded through an intermolecular pathway leading to a bornylamine–HB(C₆F₅)₂ adduct. When the starting enamine is present in excess over HB(C₆F₅)₂, the produced bornylamine–HB(C₆F₅)₂ adduct breaks up, eliminating free bornylamine and forming the initial camphorenamine– HB(C₆F₅)₂ pair. This results in hydrogenation of the camphorenamine framework in a catalytic fashion.     

Synthesis of the antiproliferative agent hippuristanol and its analogues via Suárez cyclizations and Hg(II)-catalyzed spiroketalizations

A full account of the synthesis of hippuristanol and its analogues is described. Hecogenin acetate was identified as a suitable and economical starting material for this work, and substrate-controlled stereoselection was obtained throughout the construction of the key spiroketal unit. Suárez cyclization was first used, but Hg(II)-catalyzed spiroketalization of the 3-alkyne-1,7-diol motif was finally identified as the most convenient strategy.