New polydentate ligands based on sterically hindered o-benzoquinones (pyrocatechols) containing the 1,4-diazadiene group

New bifunctional ligands containing the 1,4-diazadiene and 1,2-benzoquinone groups were synthesized by the reactions of 4-amino-3,6-di-tert-butylpyrocatechol with glyoxal and its derivatives. Their o-semiquinone complexes with transition and nontransition metals were studied in solution by the ESR method.     

Formation and structures of 2,5-di-<Emphasis Type="Italic">tert</Emphasis>-butylcyclopentadienone dimers

The structures of dimers formed from 2,5-di-tert-butylcyclopentadienone in the reaction with alkaline metals and in the Diels-Alder reaction were studied. A photochemical rearrangement with ring contraction was found for the second dimer. Spectral features of the dimers related to steric hindrance were studied by 1D and 2D NMR procedures.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2179–2183, October, 2004.     

Preparation of sodium and bisarenechromium fullendes containing esters of ethylene glycol,diethylene glycol,crown ethers,methoxyarenes, and N-ethyl-N-phenylbenzamide

Russian Chemical Bulletin - The sodium and bis(arene)chromium salts of monosubstituted hydrofullerides, containing bis(3,4-dimethoxyphenyl)phenylmethane, 2,6-bis(4-methoxyphenyl)-4-phenylpyridine,...     

Oxidation by oxygen and sulfur of Tin(IV) derivatives containing a redox-active o-amidophenolate ligand

Oxidation of tin(IV) o-amidophenolate complexes [Sn(ap)Ph(2)] (1) and [Sn(ap)Et(2)(thf)] (2) (ap=dianion of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone (ImQ)) with molecular oxygen and sulfur in toluene solutions was investigated. The reaction of oxygen with 1 at room temperature forms a paramagnetic derivative [Sn(isq)(2)Ph(2)] (3) (isq=radical anion of ImQ) and diphenyltin(IV) oxide [{Ph(2)SnO}(n)]. Interaction of 1 with sulfur gives another monophenyl-substituted paramagnetic tin(IV) complex, [Sn(ap)(isq)Ph] (4), and the sulfide, [Ph(3)Sn](2)S. The oxidation of 2 with oxygen and with sulfur proceeds through the derivative [Sn(isq)(2)Et(2)] (7), which undergoes alkyl elimination to give two new tin(IV) compounds, [Sn(ap)(isq)Et] (5) and [Sn(ap)(EtImQ)Et] (6) (EtImQ=2,4-di-tert-butyl-6-(2,6-diisopropylphenylimino)-3-ethylcyclohexa-1,4-dienolate ligand), respectively, along with the corresponding alkyltin(IV) oxide and sulfide. Complexes 3-5 and 7 were studied by EPR spectroscopy. The structures of 3, 4 and 6 were investigated by X-ray analysis.     

Hydroamination of 2-vinylpyridine,styrene, and isoprene with pyrrolidine catalyzed by alkali and alkaline-earth metal complexes

The complexes (dpp-bian)Mg(thf)₃, (dpp-bian)Ca(thf)₄ and (dpp-bian)Mg(pyr)₃ (dpp-bian is the 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene dianion; pyr is the pyrrolidine) catalyze the addition of pyrrolidine to 2-vinylpyridine at room temperature. The compound (dppbian)Mg[N(SiMe₃)₂] containing a dpp-bian radical anion catalyzes the addition of pyrrolidine to styrene at 60 °C. The dpp-bian radical anion lithium-sodium salt [(dpp-bian)Li{N-(SiMe₃)₂}][Na(C₇H₈)] is an active catalyst of the addition of pyrrolidine to styrene and isoprene at 60 °C. In all the case, the content of the catalyst was from 1 to 2 mol.%. For styrene and 2-vinylpyridine, the reactions proceeded with the formation of anti-Markovnikov addition product, while 1,4-addition product was obtained in the case of isoprene.     

A new procedure for preparing butyl acrylate-vinyl n-butyl ether copolymer as effective thickening additive to oils

The possibility of preparing copolymers by radical copolymerization on adding an active monomer, butyl acrylate, to refluxing inactive vinyl n-butyl ether was examined. The copolymer composition was studied by IR and NMR spectroscopy and by gravimetric analysis. The molecular weight and polydispersity coefficient of the copolymer were determined.     

N,N′-Disubstituted phenanthrene-9,10-diimines: synthesis and NMR spectroscopic study

Novel aryl-aryl, alkyl-alkyl, aryl-alkyl N,N′-disubstituted phenanthrene-9,10-diimines were synthesized by condensation of 9,10-phenanthrenequinone with primary amines. The novel two-stage method of synthesis of disubstituted phenanthrene-9,10-diimines with identical or different aryl and alkyl substituents at the nitrogen atom was established. The investigated compounds undergo slow Z-E/E-Z interconversion which was studied by NMR spectroscopy. Thermodynamic parameters of interconversion were obtained by variable temperature NMR spectroscopy.     

Reaction of 3,4,6-Triisopropyl-<Emphasis Type="Italic">о</Emphasis>-benzoquinone with 3,4,6-Triisopropylcatechol

Formation of protonated 3,4,6-triisopropylsemiquinone radicals in solution of a mixture of 3,4,6- triisopropyl-о-benzoquinone and 3,4,6-triisopropylcatechol was shown using ESR spectroscopy. Heating the mixture to 110°С leads to the formation of the condensation products, additional amount of 3,4,6-triisopropylcatechol, and evolution of propylene. Mathematical simulation of the kinetics of the reaction was performed.     

Catalytic C-phenylation of methyl acrylate with tetraphenylantimony(v) halides and carboxylates

Catalytic C-phenylation of methyl acrylate to methyl cinnamate with the Ph₄SbX complexes (X = F, Cl, Br, OH, OAc, O₂CEt) in the presence of the palladium compounds PdCl₂, Pd(OAc)₂, Pd₂(dba)₃, Pd(Ph₃P)₂Cl₂, and Pd(dppf)Cl₂ (dba is dibenzylideneacetone and dppf is bis(diphenylphosphinoferrocene)) was studied in organic solvents (MeCN, THF, DMF, MeOH, and AcOH). The highest yield of methyl cinnamate (73% based on the starting organometallic compound) was obtained for the Ph₄SbCl—PdCl₂ (1 : 0.04) system in acetonitrile.     

Beckmann rearrangement of the E isomer of cis-4,6,6-trimethylbicyclo[3.1.1]-heptan-2-one oxime

The individual E isomer of 4,6,6-trimethylbicyclo[3.1.1]heptan-2-one oxime has been obtained, and its transformations under the conditions of acid catalysis have been studied. The action of sulfuric acid on a solution of the oxime in acetonitrile leads to the selective formation of 5,7,7-trimethyl-2-azabicyclo[4.1.1]octan-3-one, while the action of hydrochloric acid with heating gives 4-isopropyl-3-methylaniline.Institute of Physical Organic Chemistry, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 29–32, January–February, 1991.