scholarly journals A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

2021 ◽  
Vol 17 ◽  
pp. 1509-1517
Author(s):  
Greta Utecht-Jarzyńska ◽  
Karolina Nagła ◽  
Grzegorz Mlostoń ◽  
Heinz Heimgartner ◽  
Marcin Palusiak ◽  
...  
Keyword(s):  
Visible Region ◽  
Pyrazole Derivatives ◽  
Low Intensity ◽  
Medium Intensity ◽  
Aerial Oxidation ◽  
Nitrile Imines ◽  
Moderate Yield

In-situ-generated N-aryl nitrile imines derived from trifluoroacetonitrile efficiently react with polycyclic 1,4-quinones, yielding fused pyrazole derivatives as the exclusive products. The reactions proceed via the initially formed [3 + 2]-cycloadducts, which undergo spontaneous aerial oxidation to give aromatized heterocyclic products. Only for 2,3,5,6-tetramethyl-1,4-benzoquinone, the expected [3 + 2]-cycloadduct exhibited fair stability and could be isolated in moderate yield (53%). The presented method offers a straightforward access to hitherto little known trifluoromethylated polycyclic pyrazoles. All products were isolated as pale colored solids with medium-intensity absorption maxima in the range of 310–340 nm for naphthoquinone-derived products and low-intensity bands in the visible region (≈400 nm) for the anthraquinone series.

A Convenient Synthesis of Tetrasubstituted Pyrazoles from Nitrile Imines and 2-(Thioxothiazolidin-5-ylidene)acetates

Synlett ◽  
2018 ◽  
Vol 29 (07) ◽  
pp. 918-921 ◽  
Author(s):  
Issa Yavari ◽  
Zohreh Taheri ◽  
Maryam Naeimabadi ◽  
Samira Bahemmat ◽  
Mohammad Halvagar
Keyword(s):  
Double Bond ◽  
Dipolar Cycloaddition ◽  
Pyrazole Derivatives ◽  
X Ray ◽  
X Ray Crystallography ◽  
Hydrazonoyl Chlorides ◽  
Convenient Synthesis ◽  
Nitrile Imines ◽  
Fast Access

Alkyl 2-(3-alkyl-4-oxo-2-thioxothiazolidin-5-ylidene)acetates react with hydrazonoyl chlorides in the presence of triethylamine to ­afford tetrasubstituted pyrazole derivatives. Formally, this transformation is regarded as a 1,3-dipolar cycloaddition of the exocyclic carbon–carbon double bond of the thioxothiazolidine derivatives with nitrile imines generated in situ. This efficient method provides fast access to a range of structurally diverse pyrazoles. The structure of a typical product is confirmed by X-ray crystallography.

scholarly journals Non-Selective Dimerization of Vinyl Silanes by the Putative (Phenanthroline)PdMe Cation to 1,4-Bis(trialkoxysilyl)butenes

Inorganics ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 102
Author(s):  
Sandun Perera ◽  
Michael Findlater
Keyword(s):  
Nmr Spectroscopy ◽  
Palladium Complex ◽  
Organic Products ◽  
Vinyl Silanes ◽  
In Situ Nmr Spectroscopy ◽  
In Situ Nmr ◽  
Moderate Yield

Activation of the dialkylpalladium complex (phen)Pd(CH3)2 (phen = 1,10-phenanthroline) with B(C6F5)3 affords a competent catalyst for the dimerization of vinyl silanes. All organic products of the catalytic dimerization of trialkoxyvinylsilanes were characterized by in situ NMR spectroscopy and GC–MS. The putative palladium cation was characterized by NMR spectroscopy. Upon activation, the palladium complex generated products in moderate yield (60–70%) and selectivity (~60:40, dimer:disproportionation products).

scholarly journals Selective benzylic C–H monooxygenation mediated by iodine oxides

2019 ◽  
Vol 15 ◽  
pp. 602-609
Author(s):  
Kelsey B LaMartina ◽  
Haley K Kuck ◽  
Linda S Oglesbee ◽  
Asma Al-Odaini ◽  
Nicholas C Boaz
Keyword(s):  
Selective Oxidation ◽  
High Yield ◽  
Hypervalent Iodine ◽  
Iodine Species ◽  
Mechanistic Analysis ◽  
Substrate Tolerance ◽  
Iodine Oxides ◽  
Moderate Yield

A method for the selective monooxdiation of secondary benzylic C–H bonds is described using an N-oxyl catalyst and a hypervalent iodine species as a terminal oxidant. Combinations of ammonium iodate and catalytic N-hydroxyphthalimide (NHPI) were shown to be effective in the selective oxidation of n-butylbenzene directly to 1-phenylbutyl acetate in high yield (86%). This method shows moderate substrate tolerance in the oxygenation of substrates containing secondary benzylic C–H bonds, yielding the corresponding benzylic acetates in good to moderate yield. Tertiary benzylic C–H bonds were shown to be unreactive under similar conditions, despite the weaker C–H bond. A preliminary mechanistic analysis suggests that this NHPI-iodate system is functioning by a radical-based mechanism where iodine generated in situ captures formed benzylic radicals. The benzylic iodide intermediate then solvolyzes to yield the product ester.

Parallel synthesis of meso-substituted corroles and meso-substituted [22]pentaphyrins(1.1.1.0.0) from diacyl-dipyrromethanes

2003 ◽  
Vol 07 (04) ◽  
pp. 239-248 ◽  
Author(s):  
Daniel T. Gryko ◽  
Mariusz Tasior ◽  
Beata Koszarna
Keyword(s):  
Functional Groups ◽  
Parallel Synthesis ◽  
New Method ◽  
Large Excess ◽  
Tertiary Amides ◽  
Moderate Yield ◽  
Made In

A new method was devised for the synthesis of 1,9-diacyldipyrromethanes - crucial intermediates in the synthesis of meso-substituted corroles and porphyrins with different substituents. The diacylodipyrromethanes formation involves acylation of dipyrromethanes with salts made in situ from POCl 3 and tertiary amides. This modified Vilsmeier approach gives higher yields and no concomitant formation of monoacyldipyrromethanes as compared with the Grignard route. Moreover, compounds possessing groups previously inaccessible ( CN , NO 2 etc.) can be synthesized. During optimization of the transformation of diacyldipyrromethanes into meso-substituted corroles it was found that if macrocyclization reaction mediated by DDQ is performed in the presence of large excess of pyrrole, meso-substituted [22]pentaphyrins(1.1.1.0.0) can be obtained in moderate yield. The currently described procedure constitutes a new method for the synthesis of these valuable porphyrinoids. Corroles possessing interesting, easy to transform, functional groups were obtained in 3-40% yield.

Optical Characteristics of Chemically Prepared ZnO Nanostructures on Silica Modified Polyaniline Nanocomposites

2014 ◽  
Vol 548-549 ◽  
pp. 196-200 ◽  
Author(s):  
Katherine M. Emphasis ◽  
Reynaldo M. Vequizo ◽  
Rolando T. Canditato ◽  
Majvell Kay G. Odarve ◽  
Filchito Renè G. Bagsican ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Fourier Transform ◽  
Ftir Spectroscopy ◽  
Chemical Bath Deposition ◽  
In Situ Polymerization ◽  
Visible Region ◽  
Optical Characteristics ◽  
Zno Nanostructures ◽  
Vis Spectroscopy

Zinc oxide (ZnO) on silica modified polyaniline (SM-PANI) was prepared via chemical bath deposition and in situ polymerization. The optical characteristics of the nanocomposites were investigated using ultraviolet-visible (UV-Vis) spectroscopy. The bands showed higher absorbance in the visible region. Fourier transform infrared (FTIR) spectroscopy revealed that there is an interaction between SM-PANI and ZnO.

3D Ln–Organic Frameworks Featuring Lantern-Shaped Dihelicate Chains: Synthesis and Magnetic and Photophysical Properties

2016 ◽  
Vol 69 (9) ◽  
pp. 1062 ◽  
Author(s):  
Shengyun Liao ◽  
Peiyao Du ◽  
Yanping Zhang ◽  
Xin Fu ◽  
Wen Gu ◽  
...  
Keyword(s):  
Near Infrared ◽  
Hydrothermal Reaction ◽  
Photophysical Properties ◽  
Metal Organic Framework ◽  
Visible Region ◽  
Infrared Region ◽  
X Ray Diffraction ◽  
Topological Network ◽  
Metal Organic

The in situ hydrothermal reaction of rare earth nitrate (Ln(NO3)3), 5-(4-carboxyl-1H-1,2,3-triazol-1-yl) isophthalic acid (H3ctia), and (NH4)2C2O4 resulted in the formation of a series of 3D 4f coordination polymers ([Ln(tia)(C2O4)0.5(H2O)]) (Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6), and tia2– = 5-(1H-1,2,3-triazol-1-yl) isophthalate). The results of single crystal X-ray diffraction reveal that the dinuclear lantern sub-building units ([Ln2(CO2)4]2+) are linked by C2O42– to form dihelicate chains, which are connected by tia2– to afford a novel 3D metal–organic framework with an unordinary 3-nodal (2,3,8)-connected topological network with the Schläfli symbol of {4.62}2{42.616.89.10}{6}. Complexes 2, 3, 5, and 6 exhibit strong fluorescent emissions in the visible region and complexes 1, 2, and 6 show characteristic fluorescent emissions in the near-infrared region. In addition, the magnetic properties of complexes 4, 5, and 6 were also investigated.

Synthesis of functionalized pyrazole derivatives by regioselective [3+2] cycloadditions of N-Boc-α-amino acid-derived ynones

2018 ◽  
Vol 73 (7) ◽  
pp. 467-480 ◽  
Author(s):  
Eva Pušavec Kirar ◽  
Uroš Grošelj ◽  
Amalija Golobič ◽  
Franc Požgan ◽  
Sebastijan Ričko ◽  
...  
Keyword(s):  
Amino Acids ◽  
Nuclear Magnetic Resonance ◽  
Amino Acid ◽  
Ring Opening ◽  
Pyrazole Derivatives ◽  
X Ray Diffraction ◽  
X Ray ◽  
Acid Catalyzed ◽  
Azomethine Imines

Abstract [3+2] cycloadditions of ynones derived from glycine and (S)-alanine and some other dipolarophiles with azomethine imines, nitrile oxides, diazoacetate, and azidoacetate were studied. The dipolarophiles were obtained from α-amino acids, either by the reduction of the carboxy function with ethynylmagnesium bromide or by propiolation of the amino function. Cu-catalyzed cycloadditions of ynones to azomethine imines were regioselective and gave the expected cycloadducts as inseparable mixtures of diastereomers. In some instances, further oxidative hydrolytic ring-opening took place to afford 3,3-dimethyl-3-(1H-pyrazol-1-yl)propanoic acids. Acid-catalyzed cycloadditions of 3-butenone were also regioselective and provided mixtures of diastereomeric cycloadducts, which were separated by chromatography. In the reactions of title ynones with alkyl diazoacetates, in situ-formed benzonitrile oxides, and tert-butyl azidoacetate, all cycloadducts were obtained as single regioisomers. The structures of all novel compounds were established by nuclear magnetic resonance and X-ray diffraction.

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