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الإسم : د. أحمد محمد كامل الشيخ

الرتبة العلمية: أستاذ مشارك

المسمى الوظيفي: عضو هيئة تدريسية

المكتب 8117       الرقم الفرعي 8117

بريد الكتروني: aalsheikh@uop.edu.jo

التخصص: كيمياء تحضير المركبات

جامعة التخرج: توبنغن

المؤهل العلمي

    المؤهل العلمي

    الجامعة

    البلد

    سنة الحصول على المؤهل

    البكالوريوس
    الجامعة الاردنية
    الاردن
    1994
    الماجستير
    الجامعة الاردنية
    الاردن
    1998
    الدكتوراه
    توبنغن
    المانيا
    2004



  • Journal Paper





      Ahmed Al-sheikh, " Elimination of a Thiomethyl Substituent from an Anionic 5-Methylenebarbituric Acid Derivative by Oxidation and Substitution " , "",Vol.,No., , , 03/31/2009 :الملخص
      A. Al-Sheikh, K. Sweidan, N. Kuhn, C. Maichle-Mossmer and M. Steimann, Z. Naturforsch. 64b(3), 307-312 (2009) Download




      Ahmed Al-sheikh
      :الملخص
      A. Al-Sheikh, K. Sweidan. C. Maichle-Mossmer, M. Steimann, N. Kuhn, Z. Naturforsch. 64b(1), 101-105 (2009) Download




      Kamal Sweidan, Ahmed, " Synthesis, Structure and Reactions of 1,3-Dimethyl-bis(thiomethyl)methylenebarbituric Acid " , "Z. Naturforsch",Vol.64b,No., University of Germany, Tuebingen, Germany, 01/31/2009 :الملخص
      1,3-Dimethyl-5-bis(thiomethyl)methylenebarbituric acid (8) is obtained from 1,3-dimethylbarbituric acid and CS2/NEt3 followed by alkylation with methyl iodide. Compound 8 reacts with aqueous ammonia to give 5-amino(thiomethyl)methylene-1,3-dimethylbarbituric acid (9). With benzylamine, the thiomethyl substituent in 9 is replaced to give 5-amino(benzylamino)methylene-1,3- dimethylbarbituric acid (10) while with methanesulfonic acid the sulfonate salt 11 is formed. The crystal structures of 8 and 9 are reported. Download




      Kamal Sweidan, Ahmed, " Synthesis of Phosphorus, Arsenic and Antimony Ylides Containing the 1,3-Dimethyl-2,4,6(1H,3H,5H)-pyrimidinetrione Fragments " , "Letters in Organic Chemistry",Vol.6,No., Bentham Science Publishers Ltd, Karatchy, Pakistan, 01/01/2009 :الملخص
      The ylides Ph3E-C6H6N2O3 (7, E = P (a), As (b), Sb (c)) have been prepared through the reaction of Ph3E and 5- bromo-1,3-dimethyl-2,4,6(1H,3H,5H)-pyrimidinetrione (5-bromo-1,3-dimethylbarbituric acid) 6 in the presence of triethylamine. Their characterisation was performed by nuclear magnetic resonance (NMR), mass spectrometry (MS) and elemental analysis. Download




      Ahmad Al-Sheikha, Ka, " Synthesis and Crystal Structure of Triethylammonium 5-[(2,2-Dimethyl-4,6-dioxo-1,3-dioxan-5-ylidene)(methylthio)methyl]-1,3-dimethylpyrimidine-2,4,6-trionate " , "Z. Naturforsch",Vol.63b,No., University of Tuebingen, Tuebingen, Germany, 04/30/2008 :الملخص
      Triethylammonium 5-[(2,2-dimethyl-4,6-dioxo-1,3-dioxan- 5-ylidene)(methylthio)methyl]-1,3-dimethylpyrimidine- 2,4,6-trionate (6) is obtained as red-orange stable crystals by reaction of 5-[bis(methylthio)methylene]-2,2-dimethyl- 1,3-dioxane-4,6-dione (5) with 1,3-dimethylbarbituric acid (2) in the presence of triethylamine in excellent yield. The crystal structure of 6 confirms the negative charge to be localized at the barbituric-acid ring in its enolate form. Download




      Norbert Kuhn, Ahmad , " The Crystal Structure of –Bis (thiomethyl)methylene Meldrum's Acid " , "Z. Naturforsch",Vol.62b,No., , , 11/01/2007 :الملخص
      The crystal structure of 5-bis(thiomethyl)methylene Meldrum’s Acid (2) reveals a zwitterionic nature of the compound apparently influenced by both steric and electronic factors (triclinic space group P¯1, Z = 2, a = 5.489(1), b = 7.402(2), c = 14.329(3) A˚ ; α = 82.25(3), β = 82.08(3), γ = 78.59(3)◦; V = 561.7(2) ˚A3). Download




      KuhnN., Eichele, K.,, " Hydrogen Bonds with Cyanide Ions The Structures of 1,3-Diisopropyl-4,5-dimethylimidazolium " , "",Vol.,No., , , 11/01/2006 :الملخص
      Hydrogen Bonds with Cyanide Ions? The Structures of 1,3-Diisopropyl-4,5-dimethylimidazolium Cyanide and 1-Isopropyl-3,4,5-trimethylimidazolium Cyanide Download




      Ahmed Al-sheikh, " Dihydroimidazol-2-ylidenes and Their Main Group " , "",Vol.,No., , , 10/01/2005 :الملخص
      N. Kuhn and A. Al-Sheikh , Review of 2,3- Coor. Chem. Review, 249, 829-857 (2005). Download




      Norbert Kuhn, Ahmad , " Zwitterionic Imidazolium and Phosphonium Derivatives of Methylenemeldrum's Acid [1,2] " , "Z. Naturforsch",Vol.60b,No., , , 08/01/2005 :الملخص
      2,2-Dimethyl-4,6-dioxo-5-pyridinomethyl-1,3-dioxan-5-yl-pyridinium ylide (9) reacts with 2,3-dihydro- 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (1; R1 = iPr, R2 = Me) to give the zwitterionic imidazolium derivative 2,2-dimethyl-4,6-dioxo-5-(1,3-diisopropyl-4,5-dimethylimidazoliomethyl)- 1,3-dioxan-5-yl-imidazolium ylide (4) in good yield. Similarly, the phosphonium compound 2,2-dimethyl-4,6-dioxo-5-triphenylphosphoniomethyl-1,3-dioxan-5-yl-phosphonium ylide (5) is obtained from 9 and PPh3. The crystal structures of 4 and 5 are reported. Download




      Norbert Kuhn Prof. D, " , On the Reaction of Meldrum's Acid with Sulfur Dichloride – Synthesis and Properties of anUncommon 1,3- Dithietane " , "",Vol.,No., , , 06/01/2005 :الملخص
      The 1,3-dithietane {MelS}2 (8) is obtained from Meldrum's acid MelH2 (1, Mel = C6H6O4) and sulphur dichloride in good yield. 8 reacts with the nucleophiles PPh3 and 2,3-dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (12, Im) to give the zwitterionic compounds Mel-S-PPh3 (11) and Mel-S-Im (13). Aqueous ammonia gives the dianionic disulfide (NH4)2[Mel-S-S-Mel] (14). The crystal structures of 8, 11, and 14 are discussed. Download




      Norbert Kuhn, Ahmed , " Synthesis and Structure of Meldrum’s Olefin [1] " , "Zeitschrift für Naturforschung B",Vol.59b,No., , , 11/01/2004 :الملخص
      Diisopropylidene ethylenetetracarboxylate, Meldrum’s olefin (4, Mel2) has been prepared from [HNEt3][(Mel)2CSMe] (8) and Meldrum’s acid (1, MelH2) in moderate yield. The X-ray analysis of 4 reveals a centrosymmetrical structure in which the two six-membered rings are folded along their carboxylate carbon axes by 34.9◦) and linked by a conventional C-C double bond [1.3501(19) A° ]. The “unsymmetrical” structure of 8 is also discussed. Download




      Norbert Kuhn, Ahmed , " On the Reaction of 2,3-Dihydro-1,3-diisopropyl-4,5-6-dimethylimidazol-2-ylidene with Bromine Derivatives of Meldrum's Acid, " , "",Vol.,No., , , 08/03/2004 :الملخص
      The Imidazolium salts [ImH][MelBr] (7) and [ImBr][MelBr] (8) have been obtained from the carbene Im (5) and the Meldrum’s acid derivatives MelHBr (3) and MelBr2 (4). The crystal structure analyses of 7 and 8 reveal the presence of ion pairs linked by short OH (7: 2.163 A° ) and OBr (8: 2.872 A° ) contacts Download




      Norbert Kuhn, Ahmed , " Synthesis andStructure of a Zwitterionic Imidazolium 1,3- dioxanide[1] " , "",Vol.,No., , , 11/01/2003 :الملخص
      {Bis(methylthio)methylene}-2,2-dimethyl-4,6-dioxo-1,3- dioxane (7) reacts with cis-1,2-diamino-1,2-dicyanoethene to give 2,2-dimethyl-4,6-dioxo-5-{2-(4,5-dicyano)} imidazolio-1,3-dioxan-5-yl-imidazolium ylide (8) as a stable crystalline solid in good yield. The crystal structure of 8 × C3H6OS is discussed. Download




      Norbert Kuhn, Ahmed , " 2-Amino-1,3-dimethylimidazolium 2,2-Dimethyl-4,6-dioxo-1,3-dioxanide. First Structural Characterisation of the Anionof Meldrum’s Acid [1] " , "",Vol.,No., , , 09/01/2003 :الملخص
      2-Amino-1,3-dimethylimidazolium 2,2-dimethyl- 4,6-dioxo-1,3-dioxanide (6) has been obtained from the reaction of 2,2-dimethyl-4,6-dioxo-1,3- dioxan (1, “Meldrum’s acid”) and 2-imino-1,3-dimethylimidazoline (5) in excellent yield. The unit cell of 6 contains two crystallographically independent anions lying on crystallographic mirror planes. The structure of the anion is compared with that of compound 1. Download




      Norbert Kuhn , Ahmed, " Novel Zwitterionic Sulfides, selenides and tellurides [1] " , "",Vol.,No., , , 02/01/2003 :الملخص
      The zwitterionic compounds Im-E-Mel [9, E = S (a), Se (b), Te (c), Im = 2-{1, 3-diisopropyl-4, 5-dimethylimidazolium}, Mel = 5-{2, 2-dimethyl-4, 6-dioxo-1, 3-dioxan-5-ylide}] are obtained from the corresponding 2-chalcogeno-1, 3-diisopropyl-4, 5-dimethylimidazolines 8 and 5-bromo-2, 2-dimethyl-4, 6-dioxo-1, 3-dioxan (7) in the presence of triethylamine in excellent yields. The crystal structures of the thermally stable compounds reveal most effective charge separations from which the compounds 9 resemble closely to diaryl chalkogenides. 9b and 9c are the first selenocarbonyl and tellurocarbonyl ylides reported, to our knowledge. Download




      Norbert Kuhn, Ahmed , " A New Route to Arsonium, Stibonium and Bismuthonium 2,2- Dimethyl-4,6-dioxo-1,3-dioxanides. The Crystal Structures of Ph3E-C6H6O4 (E = As, Sb, Bi). [1], " , "",Vol.,No., , , 01/01/2003 :الملخص
      The ylides Ph3E-C6H6O4 [3; E  As (a), Sb (b), Bi (c)] have been prepared through the reaction of Ph3E and 5-bromo-2,2- dimethyl-4,6-dioxo-1,3-dioxin (4) followed by addition of triethylamine in good yields. The crystal structures of 3 are reported. Download




      Norbert Kuhn, Ahmed , " Synthesis and Structure of 1-{2,2-Dimethyl-4,6-dioxo-5-(1-pyridinio)-1,3- " , "Z. Naturforsch",Vol.58b,No., , Tuebingen, Germany, 01/01/2003 :الملخص
      2-Bromo-5,5-dimethyl-4,6-dioxo-1,3-dioxine (3) reacts with pyridine and aqueous potassium carbonate to give 1-{2,2-dimethyl-4,6-dioxo-5-(1-pyridinio)-1,3-dioxan-5-yl}pyridinium ylide (5). Download




      Norbert Kuhn, Ahmed , " Synthesis and Structure of 1,3-Diisopropyl-4,5-dimethylimidazolium N,N’-Diphenylureate [1] " , "Zeitschrift f¨ur Naturforschung",Vol.57b,No., , , 11/01/2002 :الملخص
      1,3-Diisopropyl-4,5-dimethylimidazolium diphenylureate (4) has been obtained from 2,3- dihydro-1,3-diisopropyl-3,4-dimethylimidazol-2-ylidene (3) and N,N'-diphenylurea in good yield. The crystal structure of 4 contains dimeric ureate anions linked by unsymmetrical NHN hydrogen bonds while only weak interactions are detected between the imidazolium cations and the anions. Download




      Ahmed Al-sheikh, " Determination of Nchloramines in As-Samra chlorinated wastewater and their effect on the disinfection process " , "",Vol.,No., , , 11/01/2001 :الملخص
      . M. Fayyad and A. Al-Sheikh, , Water Research, 35(5), 1304-1310. (2001). Download




      Kamal Sweidan, Qutai, " Novel Derivatives of 1,3-Dimethyl-5-methylenebarbituric Acid " , "Letters in Organic Chemistry",Vol.1,No.6, Bentham Science Publishers Ltd., Karatchy, Pakistan, 12/01/2009 :الملخص
      The ability of the pyridinium adduct of 1,3-dimethyl-5-methylenebarbituric acid (2) to undergo nucleophilic substitution reaction has been examined. Various types of nucleophiles, including cyanide, barbiturate, sulfide anions and 1,2-bis(diphenylphosphino)ethane substitute the pyridinium fragment in 2 leading to synthesis of new organic derivatives. Keywords: 1,3-dimethyl-2,4,6(1H,3H,5H)-pyrimidinetrione (1,3-dimethylbarbituric acid), zwitterionic pyridinium adduct, Download




      K. Sweidan,1 A. Al-S, " NOVEL SYNTHETIC ROUTES TO 1,3,1,3-TETRAMETHYL- HYDURILIC ACID AND TETRAMETHYLALLOXANTINE (AMALIC ACID) AND THEIR CRYSTAL STRUCTURES " , "Journal of Structural Chemistry",Vol.51,No.4, Springer Science+Business Media, Inc., Mosco, Russia, 01/01/2010 :الملخص
      1,3,1,3-Tetramethylhydurilic acid (1) and tetramethylalloxantine (5) were prepared by simple novel methods. The crystal structures of the compounds 1 and 52(DMSO) are reported. Download




      Norbert Kuhn, Ahmed , " The Structural Chemistry of 2-Methylenimidazolines [1] " , "Z. Naturforsch. ",Vol.60b,No., , , 11/01/2005 :الملخص
      The 2-methylenimidazolines ImC(CN)2 (6a – c, Im = 1,3-dialkyl-4,5-dimethylimidazol-2-ylidene) are prepared by the reaction of the imidazolium salts [ImBr]Br (5) and malodinitrile while ImC{C(O)Ph}2 (7) is obtained from ImCH2 (2) and benzoic fluoride. Both the structural data of 6b, 6c, and 7 and the 13C NMR data demonstrate the influence of steric and electronic effects on the charge separation and the nonplanar arrangement of the substituents attached at the carbon atoms of the central olefinic bond. Download




      Ahmed Al-Sheikh, Kamal Sweidan, Munjed Ibrahim, Mohammed Alarjah and Norbert Kuhn, " Synthesis of novel derivatives of pyrano[2,3-d]pyrimidine via Intramolecular cyclocondensation reaction under acidic and basic conditions " , "Letters in Organic Chemistry",Vol.9,No.6, , , 12/01/2012




      Wael Abu Dayyih, Eyad Mallah, Kamal Sweidan, Ahmed Al-Sheikh and Manfred Steimann, " Crystal structure of 1,3-diisopropyl-4,5-dimethylimidazolium oxalic acid monomethyl ester, C14H24N2O4, " , "Z. Kristallogr. NCS,",Vol.,No., , , 08/01/2013




      Eyad Mallah, Ahmed Al-Sheikh, Kamal Sweidan, Wael Abu Dayyih and Manfred Steimann,, " Crystal structure of 5- [bis(methylsulfonyl)methyl]-1,3-dimethyl-5- (methylsulfonyl) pyrimidine-2,4,6(1H,3H,5H)-trione, " , " Acta Cryst",Vol. E71,No., , , 01/01/2015




      Riad Awad, Eyad Mallah, Kamal Sweidan, Ahmed AlSheikh, Wael Abu Dayyih, and Manfred Steimann,, , " Synthesis and crystal structure of 1,3-diisopropyl-4,5- dimethylimidazolium 4-methyl-benzenesulfinate " , "J. Chem. Pharm. Res.136",Vol.6,No.12, , , 11/01/2014
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