Soluble high‐Tg polyetherimides with good flame retardancy based on an asymmetric phosphinated etherdiamine

This study focuses on preparing soluble, high‐T_g polyetherimides (PEIs) with good flame retardancy. To achieve this goal, a phosphinated aminophenol, 1‐(4‐hydroxyphenyl)‐1‐(4‐aminophenyl)‐1‐(6‐oxido‐6H‐dibenz〈c,e〉〈1,2〉oxaphosphorin‐6‐yl)ethane ( 1 ), was prepared. Then, an asymmetric etherdiamine, 1‐(4‐(4‐aminophenoxy)phenyl)‐1‐(4‐aminophenyl)‐1‐(6‐oxido‐6H‐dibenz〈c,e〉〈1,2〉oxaphosphorin‐6‐yl)ethane ( 3 ), was prepared from the nucleophilic substitution of ( 1 ) with 4‐chloronitrobenzene, followed by catalytic hydrogenation. Light colored, tough, and foldable PEIs ( 5 ) with good thermal stability, organo‐solubility, and good flame retardancy were synthesized from the condensation of ( 3 ) with various aromatic dianhydrides in N,N‐dimethylacetamide, followed by thermal imidization. Properties of the resulting PEIs were evaluated and compared with those of symmetric PEIs ( 5 ′) and polyimides ( 5 ″). The structure–property relationships were discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A convenient route to pyridones,pyrazolo[2,3‐a]pyrimidines and pyrazolo[5,1‐c]triazines incorporating antipyrine moiety

Condensation of 4‐aminoantipyrine with ethyl acetoacetate, ethyl benzoylacetate, and ethyl cyanoacetate furnished the corresponding ethyl 3‐(1,2‐dihydro‐1,5‐dimethyl‐2‐phenyl‐3‐oxo‐3H‐pyrazol‐4‐yl)aminoacrylate and 2‐cyano‐N‐[(1,2‐dihydro‐1,5‐dimethyl‐2‐phenyl‐3‐oxo‐3H‐pyrazol‐4‐yl)]acetamide derivatives. The aminoacrylates derivatives react with acetonitrile and sodium hydride to give 2‐amino‐6‐methyl‐1‐(1,2‐dihydro‐1,5‐dimethyl‐2‐phenyl‐3‐oxo‐3H‐pyrazol‐4‐yl)‐4‐pyridone. Reaction of the cyanoacetamide derivative with dimethylformamide‐dimethylacetal (DMF‐DMA) afforded 2‐cyano‐N‐[1,2‐dihydro‐1,5‐dimethyl‐2‐phenyl‐3‐oxo‐pyrazol‐4‐yl]‐2‐(N,N‐dimethylamino)methylene acetamide in high yield. Treatment of the latter with 5‐aminopyrazole derivatives afforded the corresponding pyrazolo[2,3‐a]pyrimidines. 2‐cyano‐N‐[(1,2‐dihydro‐1,5‐dimethyl‐2‐phenyl‐3‐oxo‐3H‐pyrazol‐4‐yl)]acetamide also reacts with heterocyclic diazonium salts to give the corresponding pyrazolo[5,1‐c]‐1,2,4‐triazine derivatives. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:508–514, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20046     

New and Practical Synthesis of N‐(3‐Cyano‐7‐ethoxy‐4‐oxo‐1,4‐dihydroquinolin‐6‐yl)acetamide

New and practical synthetic route of N‐(3‐cyano‐7‐ethoxy‐4‐oxo‐1,4‐dihydroquinolin‐6‐yl)acetamide ( 1 ) is described, through the cyclization of 2‐aminophenyl‐ethanone ( 12 ) with N,N‐dimethylformamide dimethylacetal. The overall yield of 1 obtained from this process is 46% (five steps) with a purity of >99% (HPLC).     

Synthesis of New 3‐(Furan‐2‐yl)‐Substituted Dibenzo‐Diazepin‐1‐one Derivatives

A new series of 3‐(furan‐2‐yl) dibenzo‐diazepin‐1‐one derivatives were synthesized by condensation of 5‐(furan‐2‐yl)‐1,3‐cyclohexanedione, o‐phenylenediamine, and aromatic aldehydes, in which in some of them existed two very close isomer compounds. All the compounds were characterized by IR, MS, ¹H NMR, and elemental analysis. Also presented were the crystal structures of 3a , 3b and 3e , which were obtained and determined by X‐ray single‐crystal diffraction.     

Synthesis of some polycyclic 1,2,4‐triazines disposing of acidic N‐H group

7‐(6‐Azauracil‐5‐yl)‐isatin 1 was converted through its thiosemicarbazone 2 to 6‐(6‐azauracil‐5‐yl)‐2,3‐dihydro‐5H‐1,2,4‐triazino[5,6‐b]indol‐3‐thione 3 and through the thiosemicarbazone of appropriate isatinic acid to 2‐(2‐thio‐6‐azauracil‐5‐yl)‐6‐(6‐azauracil‐5‐yl)‐aniline 4. The course of the cyclocondensation of this compound was studied and the reaction was found to proceed in both possible ways, resulting in a mixture of compound 3 and regioisomer 6‐(2‐thio‐6‐azauracil‐5‐yl)‐2,3‐dihydro‐5H‐1,2,4‐triazino[5,6‐b]‐indol‐3‐one 5. Substituted aniline 4 was oxidized to 2,6‐bis‐(6‐azauracil‐5‐yl)‐aniline 7 , which served for the preparation of hydrazone 8 , cyclization of which led to 1‐[2,6‐bis‐(6‐azauracil‐5‐yl)‐phenyl]‐6‐azauracil‐5‐carbonitrile 9. This is the first tricyclic 6‐azauracil with vicinal arrangement of 6‐azauracil rings.     

Synthesis and characterization of some novel 2‐{2‐[1‐(3‐substituted‐phenyl)‐1H‐1,2,3‐triazol‐4‐yl‐] ethyl}‐1‐substituted‐1H‐benzo [d] imidazole derivatives

Synthesis of some novel 2‐{2‐[1‐(3‐substitutedphenyl)‐1H‐1,2, 3‐triazol‐4‐yl‐]ethyl)‐1H‐benzo[d]‐imidazole derivatives, by the condensation of o‐phenylenediamine with 3‐(1‐(3‐substituted‐phenyl)‐1H‐1,2,3‐triazol‐4‐yl) propanoic acid and then subsequent reactions with different substituted alkyl halides as electrophiles are mentioned. The synthesized compounds were characterized by ¹H NMR, EI‐MS and IR spectroscopic techniques.     

Synthesis of some symmetrically substituted compounds derived from 1,3‐bis(6‐azauracil‐1‐yl)benzene and 1,3,5‐tris(6‐azauracil‐1‐yl)benzene

The 3,5‐bis(5‐carboxy‐6‐azauracil‐1‐yl)aniline ( 7 ) and 1,3,5‐tris(5‐carboxy‐6‐azauracil‐1‐yl)benzene ( 10 ) were prepared from 3‐amino‐5‐nitroacetanilide ( 1 ) via intermediates 2–6 . A series of other substituted 6‐azauracil derivatives 9, 11‐14 were also prepared.     

Synthesis of some new Pyridine‐based Heterocyclic Compounds with Anticipated Antitumor Activity

A novel class of 5‐amino‐N′‐(1‐(pyridin‐4‐yl)ethylidene)‐1H‐pyrazole‐4‐carbohydrazides and 8‐(pyridin‐4‐yl)pyrido[2,3‐d][1,2,4]triazolo[4,3‐a]pyrimidin‐5(1H)‐ones was synthesized from reaction of 2‐cyano‐N′‐(1‐(pyridin‐4‐yl)ethylidene)‐acetohydrazide and 7‐(pyridin‐4‐yl)‐2‐thioxo‐2,3‐dihydropyrido[2,3‐d]pyrimidin‐4(1H)‐one with the appropriate hydrazonoyl halides. Moreover, 2‐cyano‐N′‐(1‐(pyridin‐4‐yl)‐ethylidene)‐acetohydrazide was used for the synthesis of 2‐cyano‐N′‐(1‐(pyridin‐4‐yl)ethylidene)‐acrylohydrazides and 2‐oxo‐2‐(2‐(1‐(pyridin‐4‐yl)ethylidene)‐hydrazinyl)‐acetohydrazonoyl cyanides. The structures of the newly prepared compounds were confirmed by both elemental and spectral analyses as well as by alternate synthesis. The anticancer activities of the prepared compounds were screened against the hepatocellular carcinoma (HepG2) cell line, and the results showed that most of the compounds exhibit considerable activities.     

Novel One‐Pot Synthesis of Aziridines Containing Sydnone Moiety

A novel series of 1,1a‐dihydro‐1‐aryl‐2‐(3‐aryl‐sydnone‐4‐yl)‐azirino[1,2‐a] quinoxalines were prepared in a one‐pot reaction of 2,3‐dibromo‐1‐(3‐arylsydnone‐4‐yl‐)‐3‐arylpropan‐1‐one with o‐phenylenediamine employing triethylamine in ethanol. The new compounds were well characterized by IR,¹H NMR, mass spectra, and C,H,N analysis.     

Three Questionable Cases in the Chemistry of Quinoxalines and Benzodiazepines in the Way of the Syntheses of Benzimidazoles

The reaction of 3‐ethoxycarbonylmethylene‐3,4‐dihydroquinoxalin‐2(1H)‐one 5 with the Vilsmeier reagent, the treatment of 3‐(3,4‐dihydroquinoxalin‐2(1H)‐on‐3‐yl)‐1,2‐dihydro‐1,5‐benzodiazepin‐2(1H)‐one hydrochloride 7 with 10% sodium hydroxide and 3‐benzimidazoylquinoxaline‐2(1H)‐one 3 with both 1,2‐phenylenediamine dihydrochloride, and the reactions of 1,2‐phenylenediamine have been reinvestigated, and the structures of these reaction products have been revised. The aforementioned reactions have been shown to proceed with the formation of 1‐N,N‐dimethylaminomethylene‐2‐oxo‐1,2‐dihydrofuro[2,3‐b]quinoxaline 10 in the first case, the formation of 3‐[2‐(benzimidazol‐2‐on‐1‐yl)vinyl]‐1H‐quinoxalin‐2‐one 12 in the second case, and the formation of 2,3‐bis‐(1H‐benzimidazol‐2‐yl)quinoxaline 17 in the third case and not the formation of 3‐(N,N‐dimethylaminocarbonyl)furo[2,3‐b]quinoxaline hydrochloride 6 , the free base of 3‐(3,4‐dihydroquinoxalin‐2(1H)‐on‐3‐yl)‐1,2‐dihydro‐1,5‐benzodiazepin‐2(1H)‐one 7 , that is, compound 11 and benzodiazepine derivative 4 , as has been described earlier. In the third case, the formation of 2,3‐bis‐(1H‐benzimidazol‐2‐yl)quinoxaline 17 occurs according to the novel quinoxalin‐2(1H)‐one benzimidazole rearrangement discovered by us. The potential mechanisms for the investigated reactions are discussed.     

Study of the Reactivity of 6,8‐Dimethyl‐4‐oxo‐4H‐1‐benzopyran‐3‐carboxaldehyde Towards Amino‐6‐oxopyridine‐3‐carboxylate Derivatives

The condensation reactions of 6,8‐dimethyl‐4‐oxo‐4H‐1‐benzopyran‐3‐carboxaldehyde ( 1 ) with equimolar amounts of ethyl 2‐amino‐4‐(4‐chlorophenyl)‐5‐cyano‐1‐[(5,6‐diphenyl‐1,2,4‐triazin‐3‐yl)amino]‐6‐oxo‐1,6‐dihydropyridine‐3‐carboxylate ( 2 ) at different reaction conditions gave different chromanone and chromenone products 3 , 4 , 5 . Also, the condensation reactions of compound 1 with ethyl 5‐cyano‐1,2‐diamino‐4‐(3‐nitrophenyl)‐6‐oxo‐1,6‐dihydropyridine‐3‐carboxylate ( 6 ) in absolute ethanol, dry benzene, acetic acid, and/or dry xylene gave a variety of products 7 , 8 , 9 , 10 depending on the solvent used.     

Synthesis and characterization of novel soluble triphenylamine‐containing aromatic polyamides based on N,N′‐bis(4‐aminophenyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine

A new triphenylamine‐containing aromatic diamine, N, N′‐bis(4‐aminophenyl)‐N, N′‐diphenyl‐1,4‐phenylenediamine, was prepared by the condensation of N,N′‐diphenyl‐1,4‐phenylenediamine with 4‐fluoronitrobenzene, followed by catalytic reduction. A series of novel aromatic polyamides with triphenylamine units were prepared from the diamine and various aromatic dicarboxylic acids or their diacid chlorides via the direct phosphorylation polycondensation or low‐temperature solution polycondensation. All the polyamides were amorphous and readily soluble in many organic solvents such as N, N‐dimethylacetamide and N‐methyl‐2‐pyrrolidone. These polymers could be solution cast into transparent, tough, and flexible films with good mechanical properties. They had useful levels of thermal stability associated with relatively high glass‐transition temperatures (257–287 °C), 10% weight‐loss temperatures in excess of 550 °C, and char yields at 800 °C in nitrogen higher than 72%. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2810–2818, 2002     

Synthesis,Characterization and Antimicrobial Activity of 1,2‐dihydroquinoxaline‐3‐yl‐3‐Substitutedphenyl‐1H‐pyrazole‐4‐Carbaldehyde

A series of 1,2‐dihydroquinoxaline‐3‐yl‐3‐substitutedphenyl‐1H‐pyrazole‐4‐carbaldehyde were synthesized and evaluated for their antimicrobial activity against two Gram‐positive and two Gram‐negative organisms and two fungal organisms. The study has shown that pyrazole‐4‐carbaldehyde‐incorporated quinoxaline was essential for activity. Among the compounds, 5a , 5c , 5d had shown significant activity against all selected strains when compared with control. These compounds may prove useful as antimicrobial agents.     

Optimization of the Suzuki coupling reaction in the synthesis of 2‐[(2‐substituted)phenyl]pyrrole derivatives

A facile three‐step synthesis of 2‐(2‐aminophenyl)pyrrole ( 1 ) and 2‐[(2‐aminomethyl)phenyl]pyrrole ( 2 ) is reported by use of Suzuki coupling of N‐Boc‐pyrrol‐2‐yl boronic acid ( 3 ) and o‐substituted aryl halogenides, followed by hydrogenation. The Pd‐catalyzed cross‐coupling reaction is optimized to be applicable to a wide range of substitued aryl halogenides, with electron‐donating and electron‐withdrawing substituents, 5a , 5b , 5c , 5d , 5e , 5f , 5g . Moreover, Pd‐catalyzed coupling of o‐bromoaniline and 3 could be applied for the one‐step preparation of pyrrolo[1,2‐c]quinazolin‐5(6H)‐one ( 8 ). J. Heterocyclic Chem., (2011).     

Synthesis of diallyl‐containing polyimide and the effect of allyl groups on properties

A diallyl‐containing bisphenol, 1,1‐bis(3‐allyl‐4‐hydroxyphenyl)‐1‐(6‐oxido‐6H ‐dibenzo [c,e][1,2] oxaphosphorin‐6‐yl) ethane ( 1 ), was prepared by a two‐step procedure. Then, a diallyl‐containing diamine, 1,1‐bis(3‐allyl‐4‐(4‐aminophenoxy)‐phenyl)‐1‐(6‐oxido‐6H‐dibenzo [c,e][1,2] oxaphosphorin‐6‐yl)ethane ( 3 ), was prepared from the nucleophilic substitution of ( 1 ) with 4‐fluoronitrobenzene, followed by the reduction by Fe/HCl. A flexible polyimide ( 4 ) with curable diallyl linkages was prepared from the condensation of ( 3 ) and 4,4′‐oxydiphthalic anhydride in m‐cresol in the presence of isoquinoline. Curing polyimide ( 4 ) at 300 °C leads to thermosetting polyimide ( 5 ). We discussed the amounts of allyl group on T_g, coefficient of thermal expansion, and thermal stability of thermosetting polyimides, and found that thermal properties and dimensional stability of thermosetting polyimides increase with the amounts of cured allyl moieties. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 513–520     

New route for preparation of nitrosubstituted 1,2‐phenylenediamines

4‐Nitrobenzoselenadiazole was methylated with dimethylsulphate to give corresponding 1‐N‐methyl‐4‐nitrobenzoselenadiazolium methylsulphate which after alkaline ring‐opening afforded 1‐N‐methyl‐3‐nitro‐1,2‐phenylenediamine in 90% yield. This compound was also prepared from 3‐nitro‐1,2‐phenylenediamine by monomethylation through tosylation, methylation and detosylation and was confirmed and characterised as 1‐methyl‐4‐nitrobenzimidazole. Methylation of 5‐nitrobenzoselenadiazole and subsequent alkaline ring‐opening led to unseparable mixture of both methylated products.     

Convenient Synthesis of Piperazine Substituted Quinolones

A series of 1‐[(4‐hydroxy‐2‐oxo‐1‐phenyl‐1,2‐dihydroquinolin‐3‐yl)carbonyl]‐4‐(substituted) piperazines 3a–c and methyl 2‐[(4‐hydroxy‐2‐oxo‐1‐phenyl‐1,2‐dihydroquinolin‐3‐yl)carbonylamino] alkanoates 5a–d has been developed by the direct condensation of ethyl [4‐hydroxy‐2‐oxo‐1‐phenyl‐1,2‐dihydro‐3‐quinoline] carboxylate 2 with N ¹‐monosubstituted piperazine hydrochlorides or amino acid ester hydrochloride in the presence of triethyl amine. The quinolone amino acid esters 5a–d were the key intermediate for the preparation of a series of 1‐[2‐((4‐hydroxy‐2‐oxo‐1‐phenyl‐1,2‐dihydroquinolin‐3‐yl)carbonylamino)alkylcarbony]‐4‐substituted piperazine derivatives 8–11 (a‐d) via azide coupling method with amino acid ester hydrochloride.     

Facile synthesis of high‐performance poly(pyrrolone imide)s from an unsymmetric phosphinated triamine

High‐performance and flexible poly(pyrrolone imide)s (PPyIs) were firstly prepared by the reaction of dianhydrides with an unsymmetric phosphinated triamine, 1‐(3,4‐diaminophenyl)‐1‐(4‐aminophenyl)‐1‐(6‐oxido‐6H ‐dibenz <c,e> <1,2> oxaphosphorin‐6‐yl)ethane (1), which was prepared by a facile, one‐pot procedure from the reaction DOPO, 4‐aminoacetophenone in excess o‐phenylenediamine in the presence of p‐toluenesulfonic acid. Thermal properties of the resulting PPyIs were evaluated and compared with those of phosphinated polyimides with a similar structure. All of the prepared PPyIs films are tough and creasable. They display higher T_g (374–412 °C), lower coefficient of thermal expansion (34–46 ppm/°C), and better thermal stability (T_d 5 wt %: 456–477 °C, 800 °C char yield: 59–63%) than analogous phosphinated polyimides. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2709–2715     

2‐Cyano‐N‐(thiophen‐2‐yl)acetamide in Heterocyclic Synthesis: Synthesis and Antibacterial Screening of Novel Pyrido[1,2‐a]thieno[3,2‐e]pyrimidine‐2‐carboxylate Moieties

A novel series of interesting 6,8‐dicyanopyrido[1,2‐a]thieno[3,2‐e]pyrimidine‐2‐carboxylate compounds were prepared via the reaction of readily accessible 2‐cyano‐N‐(thiophen‐2‐yl)acetamide with arylidene malononitriles in pyridine in the presence of piperidine. Biological screening of the tested compounds as antibacterial agents was also studied.     

Synthesis of Some New Heterobicyclic Nitrogen Systems Bearing 7H‐1,2,4‐Triazolo[1,5‐d]tetrazol‐6‐yl Moiety for Biological Interest

Reaction of 6‐mercapto‐7H‐1,2,4‐triazolo[1,5‐d]tetrazole ( 1 ) wtih 1,2‐phenylenediamine afforded N‐{7H‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐yl}‐1,2‐phenylenediamine which was cyclized to benzimidazolyl‐1,2,4‐triazolo[1,5‐d]tetrazoles using various one‐carbon cyclizing agents. Also, the treatment of 1 with maleic anhydride or phthalic anhydride gave the corresponding thio derivatives followed by hydrazinolysis to afford the thio heterobicyclic systems. Former structures of the products have been established upon elemental and spectral analyses.