140-69-2Relevant academic research and scientific papers
Metal-Free Synthesis of 1,3,4-Oxadiazoles from N′-(Arylmethyl)hydrazides or 1-(Arylmethyl)-2-(arylmethylene)hydrazines
Shang, Zhenhua,Chu, Qianqian,Tan, Sheng
supporting information, p. 1032 - 1040 (2015/03/30)
An efficient and versatile metal-free synthesis of 1,3,4-oxadiazoles from N′-(arylmethyl)hydrazides or 1-(arylmethyl)-2-(arylmethylene)hydrazines through oxidative dehydrogenation is reported. A range of 2,5-disubstituted 1,3,4-oxadiazoles were prepared by treating N′-(arylmethyl)hydrazides with (diacetoxyiodo)benzene in acetonitrile or by treating 1-(arylmethyl)-2-(arylmethylene)hydrazines with [bis(trifluoroacetoxy)iodo]benzene in methyl tert-butyl ether. Aldehyde N-acylhydrazones and aldazines were initially generated in situ as intermediates.
Structure-activity relationship and improved hydrolytic stability of pyrazole derivatives that are allosteric inhibitors of West Nile Virus NS2B-NS3 proteinase
Sidique, Shyama,Shiryaev, Sergey A.,Ratnikov, Boris I.,Herath, Ananda,Su, Ying,Strongin, Alex Y.,Cosford, Nicholas D.P.
scheme or table, p. 5773 - 5777 (2010/04/30)
West Nile Virus (WNV) is a potentially deadly mosquito-borne flavivirus which has spread rapidly throughout the world. Currently there is no effective vaccine against flaviviral infections. We previously reported the identification of pyrazole ester derivatives as allosteric inhibitors of WNV NS2B-NS3 proteinase. These compounds degrade rapidly in pH 8 buffer with a half life of 1-2 h. We now report the design, synthesis and in vitro evaluation of pyrazole derivatives that are inhibitors of WNV NS2B-NS3 proteinase with greatly improved stability in the assay medium.
The 4-methoxybenzyl (PMB) function as a versatile protecting group in the synthesis of N-unsubstituted pyrazolones
Eller, Gernot A.,Holzer, Wolfgang
, p. 2537 - 2555 (2007/10/03)
Starting from diethyl ethoxymethylenemalonate and 4-methoxy-benzylhydrazine (PMB-NHNH2) 2-(4-methoxybenzyl)-2,4-dihydro-3H-pyrazol-3-one was prepared. Reaction of the latter with carboxylic acid chlorides/calcium hydroxide in 1,4-dioxane afforded 4-acyl-5-hydroxy-1-PMB-1H-pyrazoles, whereas with dimethylformamide diethyl acetal or benzaldehyde the corresponding (E)-4-dimethylaminomethylene or (E)-4-benzylidene products, respectively, were obtained. The PMB protecting group could be conveniently removed from the pyrazole nucleus by treatment with trifluoroacetic acid to give the N-unsubstituted pyrazolones. Detailed NMR spectroscopic investigations ( 1H, 13C, 15N) with the obtained compounds are presented.
Mechanisms of benzyl group transfer in the decay of (E)-arylmethanediazoates and aryldiazomethanes in aqueous solutions
Finneman, Jari I.,Fishbein, James C.
, p. 4228 - 4239 (2007/10/02)
Rate constants are reported for the buffer-independent decay of ten (E)-arylmethanediazoates in aqueous media at 25 °C, ionic strength 1 M (NaClO4), 4% 2-propanol, in the region of pH 4-12. The rate constants are proportional to hydrogen ion concentration at high pH and become pH independent in the low-pH region. Varying concentrations of oxyanion, amine, and hydrazine buffers over the range 0.05-0.2 M increased the pseudo-first-order rate constant for decay of the diazoates by less than 10%. The azide - water selectivities, ka/ks, for partitioning of the benzyl groups in the decay of (E)-(3,5-bis(trifluoromethyl)phenyl)methanediazoate and the (3,5-bis(trifluoromethyl)phenyl)diazomethane are determined to be 0.20 and 0.21 M-1, respectively, in phosphate buffered water and 0.27 and 0.26 M-1, respectively, in 20/80 DMSO-water. It is concluded that these two reactants decompose, in these media, via a common free diazonium ion intermediate that is formed in the case of the diazoate upon unassisted N-O bond cleavage of the diazoic acid. A common rate-limiting step is indicated for all the diazoates by the correlation line for the plot of log k1, the pH independent rate constant, against σ that has a slope q = -1.23. Product ratios for trapping of benzyl groups derived from other pairs of arylmethanediazoates and aryldiazomethanes with less electron withdrawing groups are different outside experimental error, indicating the importance of different nitrogen-separated ion pairs in these reactions. The (E)-(p-methoxy)phenyl)methane-16O-diazoate decomposes in 16O/18O water to give alcohol that has an "excess" abundance of 16O compared to solvent. Decomposition of the same compound in 50/50 trifluoroethanol-water with varying concentrations of azide indicates that azide ion appears to trap a limiting amount, ～80%, of the p-methoxybenzyl group. Quantitative analysis of the data indicates that 16% of the p-methoxybenzyl cation is trapped by solvent at the nitrogen-separated ion pair stage, in the absence of azide ion. There is a 9-fold enhancement of selectivity for trifluoroethanol at the ion pair stage that is ascribed to a proton switch initiated by the leaving hydroxide ion in the ion pair. The values of Ka/ks ～ 0.2 M-1 and kT/kH ～ 0.5-0.6 for the trifluoroethanol-water selectivity and kET/kT ～ 1 for the ethanol-trifluoroethanol selectivity are independent of substituent in the decay of arylmethanediazoates (X = H and EWG) in water, water-trifluoroethanol (50/50), and water-trifluoroethanol-ethanol (50/40/10), respectively. It is concluded from this that the productdetermining steps do not involve chemical bonding but rather rotational/translational reorientation of the nucleophiles in the first solvation sphere of the carbocation intermediates. It is concluded that the values of kH/kT = 0.5-0.6 indicate preferential solvation of the cation precursor by trifluoroethanol. It is shown that a preferential interaction for trifluoroethanol of 1 kcal/mol is required to generate the observed selectivities.
Reactions of N-Aminophthalimide With Electrophiles. II. Preparation and Properties of Araldehyde Hydrazones
Hearn, Michael J.,Lucero, Elena R.
, p. 1537 - 1539 (2007/10/02)
N-Aminophthalimide (I) reacted with a variety of aromatic aldehydes to give the related arylideneaminophthalimides (III-X), although typical ketones such as acetone and benzophenone did not under the specific conditions employed.Catalytic reduction of benzylideneaminophthalimide (III) led to N-benzylaminophthalimide (XI), a stable acid-free precursor of benzylhydrazine.
