Reaction of a stable aminoarylcarbene with 2-chloroacrylonitrile: dearomatizing cyclization rather than cyclopropanation

The reaction of a stable aminoarylcarbene with 2-chloroacrylonitrile is reported. The resulting 1/1 adduct has been spectroscopically and structurally characterized. The initial Michael addition is not followed by cyclopropane formation but by a dearomatizing cyclization affording an original bicyclic structure.     

Reaktionen von komplexliganden : XIX. Einschiebung von inaminen in chrom-alkenylcarben- und chrom-aminocarber-bindungen

1-Diethylaminopropyne reacts with pentacarbonyl[methoxy(2,2-diphenylethenyl)carbene]chromium in a stereoselective way to give pentacarbonyl-[diethylamino-E-(2-methoxy-1-methyl-4,4-diphenyl-1,3-butadienyl)carbene]-chromium via insertion of the alkyne into the metal-carbene bond. The reaction of the ynamine with pentacarbonyl[methylamino(phenyl)carbene]chromium results in insertion of the alkyne and loss of carbon monoxide to give cis-tetracarbonyl[3-aza-1-methyl-2-phenyl-2-butenyl)diethylaminocarbene]-chromium. Its structure was established by oxidative degradation in an aqueous medium to give 2-benzoyl-N,N-diethylpropanamide and finally confirmed by an X-ray analysis. The new compounds are characterized spectroscopically.     

Preparation and properties of polymers from aryl cyclic sulfonium zwitterions

A new class of zwitterionic monomers were prepared in which the positive and negative sites are cyclic sulfonium and phenolate. Thermal polymerization occurs by phenolic anionic attack upon the aliphatic carbon α to the sulfonium sulfur. Polymerization proceeds with ring opening and net loss of charge to form nonionic polymers. The monomeric zwitterions are generally hydrated, crystalline solids that are soluble in water or alcohol. Chlorination of the aromatic portion of the molecule yields nonhydrated species. The polymerizations of 1-(4-hydroxy-3-methylphenyl)tetrahydrothiophenium hydroxide inner salt (dihydrate) and 1-(3,5-dichloro-4-hydroxyphenyl)tetrahydrothiophenium hydroxide inner salt were studied. The latter monomer gave a polymer with M?_n of 46,000 when a nucleophile was present as an initiator. The physical properties of this polymer were determined. Cyclization appears to be the main mechanism of termination in the polymerization of zwitterions.     

LiTiCl3: Synthesis and thermal behaviour

LiTiCl₃ is obtained as one example within an ample solid solution, Li_24–2nTi_nCl₂₄ (?4?n?10), by synpropotionation of TiCl₃ and Ti in the presence of LiCl (2:1:3 molar ratio) in sealed tantalum tubes at 750°C. It crystallizes with the inverse spinel-type structure according to (Li_0.67)^[4](Li_0.67Ti_1.33)^[4]Cl₄ with, at 25°C, a = 1048.62(4) pm, space group Fd3m. Thermal expansion is linear with α = 4.85 × 10^?5K^?1 up to about 300°C and thereafter, when the migration of Li⁺ from tetrahedral to octahedral interstices becomes increasingly important, it exhibits a relative decrease resulting, finally, in the phase transition to a NaCl-type structure that is observed for the first time at about 575°C.     

The Chemistry of Dichloromethylenammonium Salts (“Phosgenimonium Salts”)

Dichloromethylenammonium salts, particularly dichloromethylenedimethylammonium chloride, occupy a unique place as stable but reactive building blocks for synthesis. They contain three mobile chlorine atoms activated by an amino group on the same carbon atom. These salts can be regarded as chlorinated Vilsmeier or Mannich reagents and are thus at a higher oxidation level. As in the Mannich or Vilsmeier reaction, the carbon condenses here as an electrophile with formation of C? C or C? hetero atom bonds in a variety that is still far from being exhausted.     

Thermodynamic and kinetic data for adduct formation, cis-trans isomerization and redox reactions of ML4 complexes: a case study with rhodium- and iridium-tropp complexes in d8, d9 and d10 valence electron configurations (tropp=dibenzotropylidene phosphanes)

The formation of adducts of the square-planar 16-electron complexes trans-[M(tropp(ph))(2)](+) and cis-[M(tropp(ph))(2)](+) (M=Rh, Ir; tropp(Ph)=5-diphenylphosphanyldibenzo[a,d]cycloheptene) with acetonitrile (acn) and Cl(-), and the redox chemistry of these complexes was investigated by various physical methods (NMR and UV-visible spectroscopy, square-wave voltammetry), in order to obtain some fundamental thermodynamic and kinetic data for these systems. A trans/cis isomerization cannot be detected for [M(tropp(ph))(2)](+) in non-coordinating solvents. However, both isomers are connected through equilibria of the type trans-[M(tropp(ph))(2)](+)+L<==>[ML(tropp(ph))(2)](n)<==>cis-[M(tropp(ph))(2)](+)+L, involving five-coordinate intermediates [ML(tropp(ph))(2)](n) (L=acn, n=+1; L=Cl(-), n=0). Values for K(d) (K(f)), that is, the dissociation (formation) equilibrium constant, and k(d) (k(f)), that is, the dissociation (formation) rate constant, were obtained. The formation reactions are fast, especially with the trans isomers (k(f)>1x10(5) m(-1) s(-1)). The reaction with the sterically more hindered cis isomers is at least one order of magnitude slower. The stability of the five-coordinate complexes [ML(tropp(ph))(2)](n) increases with Ir>Rh and Cl(-)>acn. The dissociation reaction has a pronounced influence on the square-wave (SW) voltammograms of trans/cis-[Ir(tropp(ph))(2)](+). With the help of the thermodynamic and kinetic data independently determined by other physical means, these reactions could be simulated and allowed the setting up of a reaction sequence. Examination of the data obtained showed that the trans/cis isomerization is a process with a low activation barrier for the four-coordinate 17-electron complexes [M(tropp(ph))(2)](0) and especially that a disproportionation reaction 2 trans/cis-[M(tropp(ph))(2)](0)-->[M(tropp(ph))(2)](+)+[M(tropp(ph))(2)](-) may be sufficiently fast to mask the true reactivity of the paramagnetic species, which are probably less reactive than their diamagnetic equilibrium partners.     

Nickel(II)-komplexe des unsubstituierten cyclobutadiens

cis- and trans-3,4-Dichlorocyclobutene (I) react with Ni(CO)₄ and AlCl₃ to give (C₄H₄)NiCl₂ · AlCl₃ (II), while the bromo- and iodo-substituted cyclobutenes (III) without AlCl₃ yield the complexes (C₄H₄)NiX₂ (IVa, X  Br; IVb, X  I). Properties of II and IV are discussed and the presence of a C₄H₄ ring attached to nickel is likely from the results obtained.     

The Chemistry of Simple Phosphorus-Carbon Compounds

With the aid of selected examples an overview is given of the development trends in phosphoruscarbon chemistry over the past few years. An attempt is made to demonstrate the relationships between various parameters and properties such as constitution, basicity, substitution by functional groups, reaction behavior etc. of the compounds. In the case of basis compounds containing methylphosphorus groups the state of development of industrially interesting processes is also outlined. In addition, the synthesis of a few bifunctional phosphorus-carbon compounds which can be employed as comonomers in the production of polymers is described.     

A novel synthesis of substituted 4H-pyrazolo[3,4-d]pyrimidin-4-ones

A novel synthesis of 4H-pyrazolo-[3,4-d]pyrimidin-4-ones is described. This approach utilizes an in situ generated iminochloride as a key precursor for amidine formation, with subsequent base-catalyzed ring closure. This method represents a mild and efficient entry into this ring system which is amenable to diversification of the core template.     

Ein biologischer Vergleich zwischen Benzol und Pyridin in kondensierten Ringsystemen

The synthesis of imidazo[4,5-b]pyridines and of [1,2,4]-triazolo[1,5-a]pyridines is described, and their biological activity in relation to the standard antiviral substance, 2-(α-hydroxybenzyl)benzimidazol, is discussed.