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All total 130 Articles be found
All total 130 Articles be foundProcess development and pilot-scale synthesis of new cyclization conditions of substituted phenylacetamides to tetrahydroisoquinoline-2-ones using Eaton's reagent
Ulysse, Luckner G.,Yang, Qiang,McLaws, Mark D.,Keefe, Daniel K.,Guzzo, Peter R.,Haney, Brian P.
, p. 225 - 228 (2010)
Tetrahydroisoquinoline is a ubiquitous structural framework presented in numerous pharmacologically relevant molecules. Although accessible by the Pictet-Spengler cyclization, conditions commonly used for such cyclizations are often difficult to implement on scale. Herein, we report the development of a scaleable approach utilizing Eaton's reagent for the cyclization of substituted phenylacetamide analogues to tetrahydroisoquinoline-2-one. The development, optimization, and safety hazard evaluations, which outline the benefits and ease of workup of this new process, are discussed.
Direct meta-C?H Perfluoroalkenylation of Arenes Enabled by a Cleavable Pyrimidine-Based Template
Brochetta, Massimo,Borsari, Tania,Bag, Sukdev,Jana, Sadhan,Maiti, Siddhartha,Porta, Alessio,Werz, Daniel B.,Zanoni, Giuseppe,Maiti, Debabrata
, p. 10323 - 10327 (2019)
The development of efficient and mild methods for the synthesis of organofluorine compounds is of foremost interest in various fields of chemistry. A direct pyrimidine-based selective meta-C?H perfluoroalkenylation of arenes involving several commercially
Synthesis and antimicrobial activity of new 2-[p-substituted-benzyl]-5- [substituted-carbonyl-amino]benzoxazoles
Yildiz-Orena, Ilkay,Tekiner-Gulbas, Betul,Yalcin, Ismail,Temiz-Arpaci, Ozlem,Aki-Sener, Esin,Altanlar, Nurten
, p. 402 - 410 (2004)
A series of 23 new 2-[p-substituted-benzyl]-5-[p-substituted-phenyl/benzyl- carbonylamino]benzoxazole derivatives has been synthesized by reacting 5-amino-2-[p-substituted-benzyl]benzoxazoles with the appropriate carboxylic acid chlorides. The structures of the synthesized compounds were confirmed by IR and 1H-NMR spectral data. Antimicrobial activities of the compounds were investigated using the twofold serial dilution technique against two gram-positive and two gram-negative bacteria and three Candida species in comparison with standard drugs. Microbiological results indicated that the newly synthesized 2-[p-substituted-benzyl]-5-[p-substituted-phenyl/benzyl- carbonylamino]benzoxazole derivatives (3-25) possessed a broad spectrum of activity, showing MIC values of 6.25-200 μg/mL against the gram-positive and gram-negative microorganisms tested. Moreover, they showed significant antifungal activity with MIC values of 3.12-100 μg/mL against the Candida species tested. Especially, with a MIC value of 3.12 μg/mL, 2-benzyl-5-[p-bromobenzyl-carbonylamino]benzoxazole 9 displayed the same activity against C. glabrata as the standard drug myconazol.
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Carpino
, p. 96 (1957)
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Comparative reactivity of N′-(5-benzoyl/ethoxycarbonyl)thiazol-2-yl- N,N-dimethylformamidines with ketenes
Singh, Parvesh,Marwaha, Alka,Singh, Harmeet,Mahajan, Mohinder P.
, p. 11999 - 12005 (2005)
The comparative account of the reactivities of N′-[(5-benzoyl and ethoxycarbonyl)thiazol-2-yl]-N,N-dimethylformamidines (1a and 1b), tremendously influenced by the electronic nature of the substituents on C-5 of the thiazolic ring with various monosubstituted and conjugated ketenes is reported herein. The DA cycloadditions of the dienyl pyrimidinone 3h with both symmetrical as well as unsymmetrical dienophiles leading to the formation of various thiazolic pyrimidinone derivatives are also reported.
Photochemistry of N-hydroxypyridine-2-thione derivatives: Involvement of the 2-pyridylthiyl radical in the radical chain reaction mechanism
Aveline, Béatrice M.,Kochevar, Irene E.,Redmond, Robert W.
, p. 9699 - 9708 (1995)
The primary and subsequent photochemistry of four N-hydroxypyridine-2-thione esters has been investigated by laser flash photolysis (λexc = 355 nm). A simple, high-yield synthetic method is given for their preparation with high purity. UV irradiation of these ester compounds was shown to lead specifically to the formation of benzyl, diphenylmethyl, tert-butyl, and benzoyloxyl radicals in addition to the 2-pyridylthiyl radical. In all cases, the initial photoinduced nitrogen-oxygen bond cleavage was found to occur in high quantum yield (ΦN-O ≈ 0.5). The radical species generated by this process (2-pyridylthiyl radical and carbon-centered or oxygen-centered radicals) were characterized and their reactivity toward several radical scavengers has been studied. An efficient delayed depletion of the N-hydroxypyridine-2-thione esters was also observed, leading to overall bleaching quantum yields, ΦBl, close to unity. We have demonstrated that the delayed consumption of ground-state ester was due to the reaction of the 2-pyridylthiyl radical with its precursor, occurring with a rate constant, kr, of 3-4 × 109 M-1 s-1. This reaction, hitherto never proposed, leads to the formation of 2,2′-dipyridyl disulfide and further release of propagating radicals.
Remarkably Efficient Iridium Catalysts for Directed C(sp2)-H and C(sp3)-H Borylation of Diverse Classes of Substrates
Chattopadhyay, Buddhadeb,Hassan, Mirja Md Mahamudul,Hoque, Md Emdadul
supporting information, p. 5022 - 5037 (2021/05/04)
Here we describe the discovery of a new class of C-H borylation catalysts and their use for regioselective C-H borylation of aromatic, heteroaromatic, and aliphatic systems. The new catalysts have Ir-C(thienyl) or Ir-C(furyl) anionic ligands instead of the diamine-type neutral chelating ligands used in the standard C-H borylation conditions. It is reported that the employment of these newly discovered catalysts show excellent reactivity and ortho-selectivity for diverse classes of aromatic substrates with high isolated yields. Moreover, the catalysts proved to be efficient for a wide number of aliphatic substrates for selective C(sp3)-H bond borylations. Heterocyclic molecules are selectively borylated using the inherently elevated reactivity of the C-H bonds. A number of late-stage C-H functionalization have been described using the same catalysts. Furthermore, we show that one of the catalysts could be used even in open air for the C(sp2)-H and C(sp3)-H borylations enabling the method more general. Preliminary mechanistic studies suggest that the active catalytic intermediate is the Ir(bis)boryl complex, and the attached ligand acts as bidentate ligand. Collectively, this study underlines the discovery of new class of C-H borylation catalysts that should find wide application in the context of C-H functionalization chemistry.
Carbon dots as photocatalysts for organic synthesis: Metal-free methylene-oxygen-bond photocleavage
Cailotto, Simone,Negrato, Matteo,Daniele, Salvatore,Luque, Rafael,Selva, Maurizio,Amadio, Emanuele,Perosa, Alvise
supporting information, p. 1145 - 1149 (2020/03/11)
We report for the first time that irradiation of four different citric acid-derived carbon dots (CDs), in the absence of any other redox mediators, promotes an organic reaction. In this proof-of-concept study methylene-oxygen bond reductive photocleavage in N-methyl-4-picolinium esters is demonstrated. Cyclic voltammetry and UV-Vis spectra of the CDs and of the esters indicate that photocleavage reactivity correlates with the redox properties and the relative energies expressed in the Fermi scale. A photo-fragmentation mechanism is proposed. This study offers a new possibility to employ inexpensive and readily available CDs to promote photo-organic reactions.
