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Ammonium Thiocyanate (ammonium + thiocyanate)
Selected AbstractsSynthesis of Some Novel Thioxanthenone-Fused Azacrown Ethers, and Their Use as New Catalysts in the Efficient, Mild, and Regioselective Conversion of Epoxides to , -Hydroxy Thiocyanates with Ammonium ThiocyanateHELVETICA CHIMICA ACTA, Issue 7 2007Hashem Sharghi Abstract The regioselective ring-opening reactions of some epoxides with ammonium thiocyanate in the presence of a series of new 9H -thioxanthen-9-one-fused azacrown ethers, i.e., 7,11 (Scheme,1), and also of dibenzo[18]crown-6 (12), Kryptofix®22 (13), and benzo[15]crown-5 (14) were studied (Tables 1 and 2). The epoxides were subjected to cleavage by NH4SCN in the presence of these catalysts under mild conditions in various aprotic solvents. Reagents and conditions were identified for the synthesis of individual , -hydroxy thiocyanates in high yield and with more than 90% regioselectivity. The results can be discussed in terms of a four-step mechanism (Scheme,2): 1) formation of a complex between catalyst and NH4SCN, 2) release of SCN, from the complex, 3) reaction of the released SCN, at the sterically less hindered site of the epoxide, and 4) regeneration of the catalyst. The major advantages of this method are the high regioselectivity, the simple regeneration of the catalyst, the reuse of it through several cycles without a decrease of activity, and the ease of workup of the reaction mixtures. [source] An expedient synthesis of novel, fused pyrimido[4,5- d]pyrimidine and pyrimido [5,4- e] [1,2,4]triazolo[4,3- c]pyrimidine analogues from 4-amino-2,6-dichloro-pyrimidineHETEROATOM CHEMISTRY, Issue 4 2006Pratibha Sharma A number of potent pyrimido[4,5-d]pyrimidine have efficiently been synthesized by the condensation of 4-amino-2,6-dichloropyrimidine with various substituted benzaldehyde followed by cyclization with ammonium thiocyanate. Also, these newly synthesized derivatives were utilized for the construction of novel pyrimido[5,4-e][1,2,4]triazolo[4,3-c]pyrimidine analogues via oxidative cyclization involving 1,5-hydrogen abstraction. Structure of all the newly constructed derivatives was corroborated by the elemental and spectral data. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:245,253, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20177 [source] Humoral immune response in early-onset periodontitis: influence of smokingJOURNAL OF PERIODONTAL RESEARCH, Issue 4 2001J. Mooney Sixty-five patients with generalised early-onset periodontitis (G-EOP)(age range 16,42 years, 32 smokers and 33 non-smokers) were assessed for antibody titres and avidity to a panel of five suspected periodontal pathogens (Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Prevotella intermedia, Treponema denticola and Bacteroides forsythus). Thirty-four of these patients were untreated (17 smokers and 17 non-smokers), and thirty-one were in the maintenance phase of periodontal therapy (15 smokers and 16 non-smokers). Previous studies have investigated the effect of smoking on IgG levels in periodontitis patients in the context of the more extensive periodontal destruction seen in smokers. Based on this literature our hypothesis was that smokers would have depressed serum IgG levels directed against recognised periodontal pathogens compared with non-smokers. Antibody titres were measured by ELISA deploying fixed whole cells as coating. The IgG response was detected with biotin-anti-human IgG and avidin-peroxidase; avidity was determined by elution with ammonium thiocyanate. Median titres to A. actinomycetemcomitans, P. intermedia and T. denticola were significantly lower in maintenance patient smokers (p=0.02, 0.02 and 0.002 respectively) but not in untreated patients. Avidity to P. gingivalis was also lower in smoking maintenance patients (p=0.003) but not in untreated patients. These findings may imply some interruption of immune maturation in smokers following periodontal treatment. [source] Intramolecular, Reductive Cyclization of ,-Ketoisothiocyanates Promoted by Using Samarium DiiodideCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2005Min Seok Cho Abstract A novel samarium diiodide (SmI2) promoted intramolecular cyclization of ,-ketoisothiocyanate, derived from ,,,-unsaturated esters and ammonium thiocyanate led to ,-hydroxythiolactams and/or thiolactams in high yields. Treatment of ,-ketoisothiocyanate with two equivalents of SmI2 gave a mixture of ,-hydroxythiolactam and thiolactam. Four equivalents of SmI2 afforded only thiolactam in high yields. The intramolecular cyclization took place with high to complete stereoselectivity. A mechanism to explain this transformation is proposed. [source] | ||||||||||