Polyesters based on bromine-containing bis(p-methoxycarbonylphenoxymethyl)-methylphosphine oxide

A phosphorus- and bromine-containing bifunctional monomer has been prepared from bis(chloromethyl)methylphosphine oxide and the sodium salt of methyl 3-bromo-4-hydroxybenzoate. From this monomer, bis(2-bromo-4-methoxycarbonylphenoxymethyl)methylphosphine oxide and glycols, polyesters have been obtained by transesterification in the melt. Similarly, using dimethyl terephthalate and ethylene glycol, copolymers containing different amounts of Br and P have been prepared. They are actually polyethyleneterephthalates containing different amounts of phosphorus and bromine. The critical oxygen index is used in the evaluation of the resistance of copolyesters to combustion. It is shown that the P- and Br-containing copolyesters possess a significantly higher resistance to combustion than similar P- and P- and Cl-containing polymers with the same P content.     

Selective C-3 lithiation of 2,3-dibromo- and 2,3-diiodo-1-methylindoles

Reaction of 2,3-dibromo-1-methylindole with tert-butyllithium at −78 °C followed by treatment with tropylium ion gave 2-bromo-3-cycloheptatrienyl-1-methylindole in a moderate yield, indicating that 2-bromo-3-lithio-1-methylindole would be involved as an intermediate instead of 3-bromo-2-lithio-1-methylindole. The structure of 2-bromo-3-cycloheptatrienyl-1-methylindole was unequivocally determined by a single X-ray analysis. 2,3-Diiodo-1-methylindole also gave a 3-lithio derivative exclusively.     

Brominated trimetrexate analogues as inhibitors of pneumocystis carinii and toxoplasma gondii dihydrofolate reductase

Five previously undescribed trimetrexate analogues with bulky 2′-bromo substitution on the phenyl ring were synthesized in order to assess the effect of this structure modification on dihydrofolate reductase inhibition. Condensation of 2-[2-(2-bromo-3,4,5-trimethoxyphenyl)ethyl]-1,l-dicyanopropene with sulfur in the presence of N,N-diethylamine afforded 2-amino-5-(2′-bromo-3′,4′,5′-trimethoxybenzyl)-4-methyl-thiophene-3-carbonitrile ( 15 ) and 2-amino-4-[2-(2′-bromo-3′,4′,5′-trimethoxyphenyl)ethyl]thiophene-3-car-bonitrile ( 16 ). Further reaction with chloroformamidine hydrochloride converted 15 and 16 into 2,4-diamino-5-(2′-bromo-3′,4′,5′-trimethoxybenzyl)-4-methylthieno[2,3-d]pyrimidine ( 8a ) and 2,4-diamino-4-[2-(2′-bromo-3′,4′,5′-trimethoxyphenyl)ethylthieno[2,3-d]pyrimidine ( 12 ) respectively. Other analogues, obtained by reductive coupling of the appropriate 2,4-diaminoquinazoline-6(or 5)-carbonitriles with 2-bromo-3,4,5-trimethoxyaniline, were 2,4-diamino-6-(2′-bromo-3′,4′,5′-trimethoxyanilinomethyl)-5-chloro-quinazoline ( 9a ), 2,4-diamino-5-(2′-bromo-3′,4′,5′-trimethoxyanilinomethyl)quinazoline ( 10 ), and 2,4-diamino-6-(2′-bromo-3′,4′,5′-trimethoxyanilinomethyl)quinazoline ( 11 ). Enzyme inhibition assays revealed that space-filling 2′-bromo substitution in this limited series of dicyclic 2,4-diaminopyrimidines with a 3′,4′,5′-trimethoxyphenyl side chain and a CH₂, CH₂CH₂, or CH₂NH bridge failed to improve species selectivity against either P. carinii or T. gondii dihydrofolate reductase relative to rat liver dihydrofolate reductase.     

Electrochemical Reduction of Mono- and Dihalothiophenes at Carbon Cathodes in Dimethylformamide. First Example of an Electrolytically Induced Halogen Dance

Cyclic voltammetry and controlled-potential electrolysis have been employed to probe the electrochemical reduction of a number of mono- and dihalothiophenes at carbon cathodes in dimethylformamide containing tetramethylammonium perchlorate. Reduction of 2-bromo-, 3-bromo-, 2-chloro-, 3-chloro-, and 2-iodothiophene gives rise to a single irreversible cyclic voltammetric wave for each compound that corresponds to the two-electron cleavage of the carbon-halogen bond, and thiophene is obtained as the only product. Cyclic voltammograms for the reduction of 2,3-dibromo-, 2,4-dibromo-, 2,5-dibromo-, 3,4-dibromo-, 2-bromo-5-chloro-, and 3-bromo-2-chlorothiophene each exhibit a pair of irreversible two-electron waves. Electrolyses of either 2,3-dibromo- or 2,4-dibromothiophene at potentials corresponding to the first voltammetric wave yield a two-to-one mixture of 3-bromo- and 3,4-dibromothiophene; under similar conditions, electrolyses of 2,5-dibromothiophene give a mixture of 2-bromo-, 3-bromo-, and 3,4-dibromothiophene, electrolyses of 2-bromo-5-chlorothiophene afford a mixture of 3-bromo-, 3,4-dibromo-, 3-bromo-2-chloro-, 4-bromo-2-chloro-, and 2-chlorothiophene, and electrolyses of 3-bromo-2-chlorothiophene yield 2-chlorothiophene. Aside from the last result, these product distributions appear to arise from an electrolytically induced halogen dance. When electrolyses of the dibromothiophenes and of 2-bromo-5-chloro- and 3-bromo-2-chlorothiophene are performed at potentials that correspond to the second voltammetric wave, thiophene is the only product obtained.     

Highly efficient one-pot synthesis of D-ring chloro-substituted neocryptolepines via a condensation—Pd-catalyzed intramolecular direct arylation strategy

D-ring chloro-substituted neocryptolepines have been synthesized in excellent yield starting from 3-bromo-2-chloro-1-methylquinolinium triflate via a one-pot condensation—Pd-catalyzed intramolecular direct arylation strategy involving chloroanilines. The 3-bromo-2-chloro-1-methylquinolinium triflate was obtained via methylation of commercial 3-bromo-2-chloroquinoline with methyl triflate.     

Synthesis and isomerization reaction of 2-(benzoxazol-2-yl)-1,3-tropolones

An acid-catalyzed reaction of 2-methylbenzoxazole with 3,4,5,6-tetrachloro-1,2-benzoquinone leads to 2-(benzoxazol-2-yl)-5,6,7-trichloro-1,3-tropolone and 2-(benzoxazol-2-yl)-4,5,6,7-tetrachloro-1,3-tropolone. 1,3-Tropolones upon reflux in ethyl alcohol undergo the rearrangement resulted in the seven-membered ring contraction to form ethyl 2-(benzoxazol-2-yl)-5,6-dichloro-3-hydroxybenzoate and ethyl 2-(benzoxazol-2-yl)-4,5,6-trichloro-3-hydroxybenzoate. The molecular structure of the latter was established by X-ray diffraction analysis.     

Effect of methyl substituents on the NMR spectra of aromatic protons of some nitrobenzene derivatives

Proton NMR spectra were recorded and analysed for 1-bromo-4-nitrobenzene, 2-bromo-5-nitroluene, 3-bromo-6-nitrotoluene and 2-bromo-5-nitro-p-xylene, as well as for the corresponding compounds having p-CH₃C₆H₄S in place of Br. Chemical shifts and coupling constants generally agree with expected values; however, a deshielding effect of the methyl group on aromatic protons was observed in one case.     

STEROIDAL 2-AMINO-1,3,4-THIADIAZINES AND AMINOTHIAZOLES

Abstract

The reaction of 16-bromo-17-ketones and 2-bromo-3-ketones reacted readily-upon heating for short periods of time with thiosemicarbazide in isopropanol in a 1:2 ratio to give 2-amino-1,3,4-thiadiazines. Extension of this reaction to 21-bromo-33-hydroxy-5-pregnen-20-one produced the corresponding thiadiazine.     

Synthesis of trisubstituted thiophenesvia a halogen dance reaction at 2-bromo-5-methylthiophene

Summary A new example of a selective halogen dance reaction was observed upon lithiation of 2-bromo-5-methylthiophene withLDA under appropriate reaction conditions. A series of 2-substituted 3-bromo-5-methylthiophenes was prepared by reacting the thus selectively generated intermediate 3-bromo-2-lithio-5-methylthiophene with various electrophiles to study scope and limitations of the reaction.Dedicated to Prof. emeritusHans Suschitzky, University of Salford, UK, on the occasion of his 80^th birthday     

Synthesis of 3,5-ditert-butyl-4-hydroxybenzoates and their thermal antioxidation behavior for polypropylene

Butyl 3,5-ditert-butyl-4-hydroxybenzoate (BB), octyl 3,5-ditert-butyl-4-hydroxybenzoate (OB), and dodecyl 3,5-ditert-butyl-4-hydroxybenzoate (DB) were synthesized and characterized, and their performance as antioxidant for polypropylene (PP) were also investigated. The thermooxidative stability of PP with different antioxidants were assessed by the measurements of long-term accelerated aging, differential scanning calorimetery, and thermogravimetric analysis. The results showed that 3,5-ditert-butyl-4-hydroxybenzoates could effectively inhibit the oxidation degradation of PP. And it was also found that the antioxidant efficiency of BB, OB, and DB for PP was in the order of DB > OB > BB.     

Nonlinear analysis of dynamic binding in affinity capillary electrophoresis demonstrated for inclusion complexes of beta-cyclodextrin

The stability of the molecular host-guest inclusion complexes of beta-cyclodextrin with benzoate and four different hydroxybenzoates is investigated. For the measurement of the binding constants an experimental method is devised that is based on affinity capillary electrophoresis (ACE) with indirect UV absorbance detection. We derive an explicit equation for effective mobilities in ACE experiments without violation of rigorous mass balance. This equation is employed in the nonlinear least-squares analyses of the experimental data yielding binding constants of 48+/-2 M(-1) for benzoate, 299+/-38 M(-1) for 2-hydroxybenzoate, 37+/-1 M(-1) for 3-hydroxybenzoate, 228+/-9 M(-1) for 4-hydroxybenzoate, and 895+/-110 M(-1) in the case of 2,4-dihydroxybenzoate.     

2-(5-Bromo-2-furyl)quinoxaline and 3-(5-bromo-2-furyl)-2-quinoxalone

2-(5-Bromo-2-furyl)quinoxaline and 3-(5-bromo-2-furyl)-2-quinoxalone were obtained by the action of bromine on the corresponding quinoxaline derivatives and also by condensation of o-phenylenediamine with, respectively, (5-bromo-2-furyl)glyoxal or (5-bromo-2-furyl)glyoxylic acid esters.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 404–406, March, 1973.     

On the reaction of methoxide ion with bromoiodothiophenes

The reaction of 3-bromo-2-iodothiophene with sodium methoxide in methanol, pyridine or hexamethylphosphoric triamide and the same reaction of 4-bromo-2-iodo- and 4-bromo-3-iodo-thiophene in pyridine led to a halogen-dance, giving the same mixture of 3-bromothiophene, bromo-iodothiophenes, diiodo-bromothiophenes and triiodo-bromothiophenes. The reaction of all three isomeric bromo-iodothiophenes with sodium methoxide in methanol in the presence of cupric oxide gave 4-bromo-2-methoxythiophene.     

Addition of hypobromous acid to 1-phenylcycloalkenes

Reaction of 1-phenylcyclooctene and 1-phenylcycloheptene with N-bromosuccinimide (NBS) in aqueous DMSO gives the corresponding 3-bromo-2-phenylcycloalkenes and 2-phenylcycloalk-2-enols in a ratio of 3 : 1. Unlike them, 1-phenylcyclohexene gives a mixture of 3-bromo-2-phenylcyclohexene and 2-bromo-l-phenylcyclohexanol. The oxidation of allylic alcohols with pyridinium chlorochromate afforded the corresponding α,β-unsaturated ketones.     

A facile synthesis of methyl 2-substituted-4-benzoxazolecarboxylates

Methyl 2-substituted-4-benzoxazolecarboxylates were synthesized from methyl 2-amino-3-hydroxybenzoate and the corresponding acid chloride or ortho acetal with pyridinium p-toluenesulfonate as an acid catalyst. Decomposition due to hydration at the 2-position was seen for some compounds during purification.     

Regioselective synthesis of ω-bromo-3-ketosulfones, ω-bromo-3-ketonitriles and 2-(ω-bromoalkyl)benzofurans based on a ‘ring-closing/ring-opening’ strategy

ω-Bromo-3-ketosulfones, ω-bromo-3-ketonitriles and various functionalized 2-(ω-bromoalkyl)benzofurans were chemo- and regioselectively prepared by application of a ‘ring-closing/ring-opening’ strategy. The cyclization of 3-ketosulfone and 3-ketonitrile dianions with 1-bromo-2-chloroethane or 1,4-dibromobut-2-ene afforded functionalized 2-alkylidenetetrahydrofurans which were subsequently cleaved by reaction with boron tribromide or boron trichloride to give the final products.     

Reactions of 1-aryl-2-bromo-3,4,4-trichlorobut-3-en-1-ones with some nucleophilic reagents

Reactions of 2-bromo-1-phenyl- and 2-bromo-1-(4-methylphenyl)-3,4,4-trichlorobut-3-en-1-ones with morpholine and diethylamine are accompanied by prototropic allylic rearrangement, leading to 3-amino-1-aryl-2-bromo-4,4-dichlorobut-2-en-1-ones as mixtures of E and Z isomers. The title compounds react with hydrazine, hydroxylamine, and thiourea to give the corresponding 5-aroyl-4-methoxypyrazoles, 3-aryl-5-hydroxyiminomethyl-4-methoxyisoxazoles, and 2-amino-4-aryl-5-trichlorovinylthiazoles.     

Unforeseen formation of 2-bromo-3-hydroxybenzaldehyde by bromination of 3-hydroxybenzaldehyde

Contrary to literature reports, bromination of 3-hydroxybenzaldehyde can afford both 2-bromo-5-hydroxybenzaldehyde and 2-bromo-3-hydroxybenzaldehyde, but 4-bromo-3-hydroxybenzaldehyde was not detected. 2-Bromo-3-hydroxybenzaldehyde was converted into 2-(benzyloxy)-1-bromo-5-methoxy-7-methylnaphthalene. X-ray crystallographic analysis supports the identity of 2-bromo-3-hydroxybenzaldehyde.     

Reactions of 3-isopropenyltropolones with bromine and N-bromosuccinimide: Formation of 8H-cyclohepta[b]furan-8-one derivatives

3-Isopropenyltropolones 1a-c were treated with bromine in carbon tetrachloride to give 3-methyl-8H-cyclohepta[b]furan-8-ones 2a-c and their corresponding 7-bromo-substituted compounds 3a-c , while reactions in acetic acid gave the bromo-substituted compounds 3a-c . On the other hand, bromination of 1a-c with N-bromosuccinimide afforded 7-bromo-3-(2-bromo-1-methylethenyl)tropolones 5a-c . The compound 2a was treated with bromine to give 2-bromo-3-methyl-8H-cyclohepta[b]furan-8-one ( 4 ). The tropolones 5a-c were heated in the presence of potassium carbonate to give the cyclized compounds 3a-c .     

Fluorénacènes et fluorénaphènes synthèses dans la série des indéno-fluorènes,XVII. Dérivés méthylés du cis-fluorénacène,du trans-fluorénacène et du trans-fluorénaphène

By condensation of the chlorides of the three 9-oxo-fluorene-2-, -3-, and -4-carboxylic acids with 4-bromo-1,2-xylene on one side, and of the chlorides of o-bromobenzoic acid, 2-bromo-4-methyl-benzoic acid and 2-bromo-4,5-dimethyl-benzoic acid with fluorene, 2-methylfluorene and 3-methylfluorene on the other side, followed by direct or indirect cyclisation and by final reduction, several new methyl derivatives of the indenofluorenes I, II and IV are synthesized.