The vilsmeier-haack reaction. IV. Reaction of phosphorus oxychloridedimethylformamide with semicarbazones

Ketone semicarbazones react with two moles of phosphorus oxychloride-dimethylformamide with the formation of 3-substituted pyrazole-4-carboxaldehydes. Aldehyde semicarbazones give, with one mole of phosphorus oxychloride-dimethylformamide, amidazines.     

High-spin metal complexes containing a ferromagnetically coupled tris(semiquinone) ligand

The tris-bidentate ligand 1,3,5-tris(5'-tert-butyl-3',4'-dihydroxyphenyl)benzene ((TBCat)(3)Ph) was synthesized. The reaction of this molecule in basic solution with two paramagnetic acceptors, i.e., a nickel(II)minus signtetraazamacrocyclic ligand complex (Ni(CTH)) (CTH = dl-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) and manganese(II)-hydrotris[3-(4'-cumenyl)-5-methylpyrazolyl]borate (Mn(Tp(Cum,Me))), yielded two complexes whose analytical formulas are consistent with those of trinuclear complexes. Spectroscopic and magnetic measurements suggest that these derivatives contain divalent metal ions coordinated to the tris(semiquinone) form of the ligand. Analysis of the magnetic data shows that the pi-connectivity of the ligand enforces ferromagnetic coupling between the three semiquinone units of the molecule, giving rise to complexes with S = 9/2 (M = Ni(II)) and S = 6 (M = Mn(II)) ground states. The coupling within the tris(semiquinone) unit is quite large (J = -26 cm(-1) for the nickel(II) derivative and J = -40 cm(-1) for the manganese(II) one, using the general exchange Hamiltonian H = sigma J(ij)S(i)S(j)), and it is of the same order of magnitude as that observed in an analogous series of bis(semiquinone) complexes that we recently reported.     

A mechanistic study of reactions of stable disilenes with haloalkanes.

Mechanisms of the reactions of three tetrakis(trialkylsilyl)disilenes and a tetraaryldisilene with various haloalkanes such as carbon tetrachloride, chloroform, dichloromethane, which gave the corresponding 1-alkyl-2-chlorodisilanes and/or 1,2-dichlorodisilanes, were investigated in detail. As evidenced by an ESR observation of an intermediate radical, these reactions were quite unusual, forming neutral radical pairs from two closed shell molecules at the first step; no similar reactions have been observed between alkenes and haloalkanes. Low oxidation potentials of these disilenes, large negative activation entropies, and solvent effects for the rates are in good accord with the direct halogen abstraction of disilenes from haloalkanes instead of single-electron transfer at the rate-determining first step. The structure--reactivity relationship of the reactions and the Hammond postulate suggest that the transition state structures for the first step are similar to those for the halogen abstraction by silyl radicals, but more product-like.     

Central limit results for jump diffusions with mean field interaction and a common factor

A system of N weakly interacting particles whose dynamics is given in terms of jump-diffusions with a common factor is considered. The common factor is described through another jump-diffusion and the coefficients of the evolution equation for each particle depend, in addition to its own state value, on the empirical measure of the states of the N particles and the common factor. A Central Limit Theorem, as N → ∞, is established. The limit law is described in terms of a certain Gaussian mixture. An application to models in mathematical finance of self-excited correlated defaults is described.     

Structural and electronic characterization of non-heme Fe(II)-nitrosyls as biomimetic models of the Fe(B) center of bacterial nitric oxide reductase

The detoxification of nitric oxide (NO) by bacterial NO reductase (NorBC) has gained much attention as this reaction provides a paradigm as to how NO can be detoxified anaerobically in cells. However, a clear mechanistic picture of how the heme/non-heme active site of NorBC activates NO is lacking, mostly as a result of insufficient knowledge about the properties of the non-heme iron(II)-NO adduct. Here we report the first biomimetic model complexes for this species that closely resemble the coordination environment found in the protein, using the ligands BMPA-Pr and TPA. The systematic investigation of these compounds allowed us to gain key insight into the electronic structure and geometric properties of high-spin non-heme iron(II)-NO adducts. In particular, we show how small changes in the ligand environment of iron could be used by NorBC to greatly modulate the properties, and hence, the reactivity of this species.     

A Stable Cyclic (R2SnAu)3 Anion Having In‐Plane σ‐Möbius Aromaticity

A cyclic (R₂SnAu)₃ anion ( 3^? , R₂Sn=2,2,5,5‐tetrakis(trimethylsilyl)‐1‐stannacyclopentane‐1,1‐diyl) has been synthesized as a stable blue salt with K⁺(THF)₆ through the reaction of stable dialkylstannylene 1 with R′₃PAuCl (R′=Et, Ph) followed by the reduction with KC₈. Crystallographic and NMR analysis shows that the six‐membered (SnAu)₃ ring of 3^? is planar and highly symmetric with an equal distance of six Au?Sn bonds. A UV/Vis spectrum of 3^? in hexane reveals an intense absorption maximum at 598 nm. While cyclic Au₃^? with four valence electrons is known as unstable anti‐aromatic anion, 3^? with three divalent tin ligands is stable σ aromatic anion with an unprecedented Möbius orbital array as predicted by the perturbation MO and CCSD analysis of 3^? .     

Alkylation of Aryl and Hetaryl Ketoximes with Alkyl Iodides Prepared In Situ from Alkyl Chlorides Under Phase Transfer Catalysis Conditions

Two simple one-pot phase transfer catalytic methods for the preparation of ketoxime O-ethers from the corresponding ketoximes and alkyl iodides prepared in situ from alkyl chlorides were developed. The corresponding aryl and hetaryl ketoxime O-ethers were obtained in 15–83% yields.