Spin density distributions in radical anions of heterocyclic amine N-oxides

The unrestricted Hartree-Fock (UHF) method of Snyder and Amos is used to calculate, in the -electron approximation, the spin density distributions in radical anions of heterocyclic amine N-oxides. The computed spin densities are observed to be in good agreement with the experimental values. The computed spin density distribution of the radical anion of pyridine N-oxide is consistent with the greater susceptibility of pyridine N-oxide relative to pyridine to electrophilic nitration. Also, the calculations are consistent with the lower basicity of the N-oxides relative to the parent bases.     

4-Hydroxy-2-quinolones 131. Bromination of 3-allyl-4-hydroxy-2-oxo-1,2-dihydroquinoline

The bromination of 3-allyl-4-hydroxy-2-oxo-1,2-dihydroquinoline by molecular bromine is accompanied by the closure of a five membered furan ring and gives the corresponding 2-bromomethyl-3,9-dihydro-2H-furo[2,3-b]quinolin-4-one. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1677–1686, November, 2007.     

An efficient, rapid and regioselective nuclear bromination of aromatics and heteroaromatics with NBS using sulfonic-acid-functionalized silica as a heterogeneous recyclable catalyst

A simple, efficient and rapid method has been developed for high-yielding regioselective nuclear monobromination of aromatic and heteroaromatic compounds using NBS in the presence of sulfonic-acid-functionalized silica at room temperature. The catalyst works under heterogeneous conditions and can be recycled.     

Synthesis of brominated 2-(tert-butyl-NNO-azoxy)anilmes

2-(tert-Butyl-NNO-azoxy)aniline was prepared by selective reduction of 2-(tert-butyl-NNO-azoxy)nitrobenzene. Its bromination yielded the correspondingpara-bromo- andortho, para-dibromoanilines (3a,b).meta-Bromoanilines (6a,b) were synthesized by selective replacement of theortho-bromine atoms in ortho,para-bromo(tert-butylazoxy)benzenes (5a,b) by ammonia in toluene under pressure.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1620–1623, September, 1994.This work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 93-03-18461).     

A simple and regioselective α-bromination of alkyl aromatic compounds by two-phase electrolysis

Electrochemical bromination of toluene and substituted toluenes by two-phase electrolysis yields the corresponding α-brominated products. The reaction has been carried out in a single compartment cell with platinum electrodes at 0 °C in chloroform using an aqueous sodium bromide solution (60%) containing a catalytic amount of HBr. Two-phase electrolysis results in high yields (60-95%) of monobromo compounds with very high regioselectivity (>95%).     

Electrophilic monofluoromethylation of O-, S-, and N-nucleophiles with chlorofluoromethane

CH₂ClF has been found to be a useful electrophilic monofluoromethylating agent for a variety of O-, S-, and N-nucleophiles. The reaction is not sensitive to the radical scavenger such as nitrobenzene, which strongly supports an S_N2 mechanism rather than an SET mechanism. Although most of these products (fluoromethyl ethers, sulfides, and amines) can be isolated with good purity, some of these compounds do intend to decompose (via defluorination) during storage. The electrophilic monofluoromethylation of carbon-nucleophiles was attempted with CH₂ClF, CH₂FI, or FCH₂OTs as monofluoromethylating agents, but with no success.     

Synthesis of 4-Pyridyl-2,3-dihydro-1H-1,5-benzodiazepin-2-ones

4-Pyridyl-2,3-dihydro-1H-1,5-benzodiazepin-2-ones were obtained by the condensation of ethyl nicotinoyl- or isonicotinoylacetates with o-phenylenediamine. Alkylation of the pyridylbenzodiazepinones with ethyl iodide under phase-transfer catalysis conditions occurred at the amide nitrogen of the heterocycle, whereas in nitromethane it occurred at the nitrogen of the pyridine substituent. Bromination with N-bromosuccinimide occurred at position 3 of the heterocycle. Pyridyldibenzodiazepinones underwent thermal rearrangement to derivatives of vinylbenzimidazole.     

Microwave-assisted rapid electrophilic fluorination of 1,3-dicarbonyl derivatives with Selectfluor

A microwave-assisted fluorination method for 1,3-dicarbonyl compounds using Selectfluor^® has been developed. 2-Monofluorinated products can be obtained in high yield in neutral reaction conditions with addition of 1 eq. of Selectfluor^®. Treatment of 1,3-dicarbonyls with 3 eq. of Selectfluor^® in the presence of tetrabutylammonium hydroxide (TBAH) as the base results in the formation of 2,2-difluorinated derivatives only.     

4-hydroxy-2-quinolones. 124. Synthesis and structure of ethyl 2-bromomethyl-5-oxo-1,2,6,7,8,9-hexahydro-5H-oxazolo-[3,2-<Emphasis Type="Italic">a</Emphasis>]quinoline-4-carboxylate

The hydrogenation of the benzene part of the molecule in N-allyl-substituted 4-hydroxy-2-quinolinones does not affect the nature of their bromination by molecular bromine and gives 2-bromomethyl-5-oxo-1,2,6,7,8,9-hexahydro-5H-oxazolo[3,2-a]quinolines. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1180–1188, August, 2007.     

Reductive opening of 1H,3H-benzo[de]isochromene: synthesis of 1,8-difunctionalised naphthalenes

The lithiation of 1H,3H-benzo[de]isochromene (6) with lithium and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5% molar) in THF at −50 °C gives dianionic intermediate 7, which by reaction with different electrophiles {H₂O, D₂O, ^tBuCHO, PhCHO, Me₂CO, (CH₃CH₂)₂CO, [CH₃(CH₂)₄]₂CO, (CH₂)₅CO, (CH₂)₇CO, (−)-menthone} at the same temperature followed by hydrolysis leads to functionalised alcohols 8. If after addition of a carbonyl compound as the first electrophile [^tBuCHO, (CH₂)₅CO, (−)-menthone], the resulting dialcoholate 9 is allowed to react at 0 °C, a second lithiation takes place to give intermediate 10 which by reaction with a second electrophile [H₂O, ^tBuCHO, (CH₂)₅CO, CO₂], yields, after hydrolysis, 1,8-difunctionalised naphthalenes 11. Cyclization under acidic conditions of diols 8e-i gives oxygen-containing eight-membered heterocycles, which are homologous to the starting material 6.