Fathi A. Abu-Shanab

POLYCYCLIC PYRIDINES: SYNTHESIS OF PYRIDOTHIENOPYRIMIDINES PYRIDOTHIENOTRIAZINES AND PYRIDOTHIENOTRIAZEPINES

Abstract Thienopyridines 3a-c were acetylated with Ac2O to afford the pyridothienopyrimidines 4a-c. Also 3a-c were treated with carbon disulfide in dioxan solution to give 5a-c. Diazotization of 3a-c gave the triazine derivatives 6a-c. Treatment of 3a-c with triethyl orthoformate in acetic acid gave 7a-c in good yield. Chlorination of 7a by POCl3, afforded the chlorine derivatives 8. Similarly diazotization of the ortho-aminohydrazide 3d give the corresponding azide 9 which was subjected to Curtius rearrangement in boiling xylene to give the imidazothienopyridine 10. Compound 12 was obtained by the reaction of 3d with either formic acid or trimethyl orthoformate. Compond 14 was also obtained by the reaction of 3d with ethyl chloroformate. Refluxing of 3d with methyl isothiocyanate gave 15. The interaction of 3d with acetylacetone furnished the pyrazolyl derivative 16. The ortho-aminonitrile 3e reacts with mixture of formic acid and formamide (1:1) to give 7a. whereas 3e reacts with formamide alone give 17. Treatment of 3e with carbon disulfide in boiling pyridine afforded 18. Also, acetylation of 3e with acetic anhydride afforded 4a. Finally, treatment of 3e with triethyl orthoformate in acetic anhydride afford 19. The reaction of 3e with phenyl isothiocyanate gave 20.

ENAMINONES AS BUILDING BLOCKS IN ORGANIC SYNTHESIS: SYNTHESIS OF NEW POLYFUNCTIONAL PYRIDINES, CONDENSED PYRIDINES, AND PENTA SUBSTITUTED BENZENE

ABSTRACT Several new thienopyridine and methylthioether derivatives have been synthesized. New synthesis of pyrido[2,3-b]-thieno[3,2-d]pyrimidine and penta substituted benzene were achieved.

Spectrophotometric and derivative spectrophotometric determination of palladium(II) using pyridopyridazine dithione in the presence of non-ionic surfactant

Pyridopyridazine dithione (PPD) was synthesized as a new sensitive and selective reagent for spectrophotometric and derivative spectrophotometric determination of palladium(II). In aqueous and micellar medium, PPD forms 1:4 complexes having molar absorptivities of 4.68 × 104 and 5.74 × 104lmol−1 cm−1 at 570 and 615 nm, respectively. Beers law was obeyed up to 2.2 and 2.5 μg ml−1 with detection limits of 0.2 and 0.1μg ml−1. The relative standard deviations for 1.23μg ml−1 were 2.6 and 1.3%, in the absence and presence of Triton X-100. In fourth-derivative mode, the regression equation, linear range, detection limit and RSD for 0.075 μg ml−1 wereD4 = 4.3C + 1.5 × 10−3, 0.013 – 0.23 μg ml−1, 3.7 ng ml−1 and 0.78%, respectively. The ionization constants of the reagent and stability constants of the complexes were evaluated. The method is free from interference by most common metal ions and anions. The method was applied for determination of palladium in activated charcoal.

Studies on heterocyclic β-enaminonitriles: Synthesis of new condensed thieno[2,3-b]pyridines containing N-heterocyclic moieties

New versatile enaminonitrile-type building blocks, 3-aminothieno[2,3-b]pyridine-2-carbonitriles 3a,b, were synthesized from 3-cyanopyridine-2-(1H)-thiones 1a,b. Interaction of 3a,b with triethyl orthoformate furnished the corresponding ethoxymethylideneamino derivatives 6a,b. Derivatives of heterocyclic systems having the pyrazole, pyrimidine, and pyridine rings were obtained from the key precursors 3a,b and 6a, respectively.

STUDIES ON THE SYNTHESIS OF SOME PYRAZOLO[1,5=a]PYRIMIDINES BEARING SULFONAMIDO MOIETIES

Abstract A novel synthesis of pyrazolo[1,5-a]pyrimidine derivatives 4,5 and 9 bearing sulfonamide moieties from the reaction of aminopyrazoles 1 with [bis(methy1sulfanyl)methylidene]malononitrile 2, [arylamino(methylsulfanyl)methylidene]malonoNtrile 6 and ethyl [bis(methylsulfanyl)methylidene]cyano acetate 7 is reported.

Synthesis of 1,4‐Diaryl‐piperazine‐2,5‐diones: New Behavior of N,N‐Dimethylformamide Dimethyl Acetal (DMFDMA)

Abstract Reactions of chloroacetamides (5) with N,N‐dimethylformamide dimethyl acetal gave 1,4‐diaryl‐piperazine‐2,5‐diones 11a–e in good yield, rather than 1,5‐diaryl‐3,7‐dimethoxy‐1H,5H‐[1,5]diazocine‐2,6‐diones (9a–e).

β-Aminocrotononitrile in heterocyclic synthesis: Synthesis of polysubstituted pyridines as precursors to bicycles and polycycles

β-aminocrotononitrile (1) reacted with either cyanothioacetamide to give (3) or malononitrile to afford an anion (5). Pyridine-2(1H)-thione (4) was obtained by boiling of (3) in ethanol and Et 3N or treatment of (5) with H 2S, respectively. The reaction of anion 5 with isothiocyanates (6) gave N-substituted pyridine-2(1H)-thiones (7). N-Substituted pyridine-2(1H)-thiones (7) can be used for the preparation of pyrido[2,3-d]pyrimidines (8a–e) and (10a–e), or the preparation of pyrido[1,2-a]pyrimidines (12a–d). 1,8-Naphthyridine derivatives (14a–d) and (16a–e) can also be obtained from pyridine-2(1H)-thione (7). Finally, 1,8-naphthyridine derivatives (16a–e) can be used for the preparation of tetracyclic compounds 17a–c and 18a,b.

Synthesis of Some Novel Benzothiazole Derivatives

Novel 1,2,4-triazine, pyridine, and benzopyran derivatives have been synthesized from N-(2-benzothiazolyl)cyanoacetamide via its reaction with some electrophiles. The structure of the synthesized compounds was established by analytical and spectral data.

Unsaturated sulfur compounds from reactions of lithiated methylazines with carbon disulfide and electrophiles

2-Methylpyridine (1a), 2,6-dimethylpyridine (1b), 2-methylpyrazine (1c) and 2-methylquinoline (1d) were treated with lithium diisopropylamide (LDA) in THF at low temperature followed by carbon disulfide to give the dianion (5). Reactions of dianion (5) with iodomethane, 1,2-dibromoethane, ethyl chloroacetate, α -chloroacetonitrile or phenacyl bromide gave 6a–c, 6e, 9, 10, 11, 12 and 13, respectively. Reactions of dianion (5) with 1,2-dibromoethene gave the dithiocarboxylic acids (14a–c) rather than a dithiolene, and reaction of dianion (5a) with aqueous ammonium persulfate gave 15. Treatment of 2-methylpyridine (1a) with lithium diisopropylamide (LDA) and 2-bromopyridine afforded tetra-2-pyridylmethane (18) as the main product.

Synthesis of polyfunctionally substituted pyridine-2-(1H)-thiones containing a sulfone moiety

1-Phenyl-2-(phenylsulfonyl)ethanone (1) reacts with DMFDMA to give enamine 2, which upon treatment with cyanothioacetamide affords 3-cyano-5-benzenesulfonyl-4-phenylpyridine-2(1H)-thione (4), a compound that can also be obtained by the reaction of 1-benzenesulfonyl-1-benzoyl-2-ethoxyethene (3) with cyanothioacetamide. The reaction of 2-thiocarbamoylacetamide (8a) and N-phenyl-2-thiocarbamoylacetamide (8b) with 3-aryl-2-benzenesulfonylacrylonitrile (9a– c) affords 10a–f. The methylation of 10d–f with methyl iodide results in the formation of S-methyl derivatives (12a–c). Compound 12c can be obtained by the reaction of 13 with 9c.