Results 21 to 30 of about 2,222 (186)

Modeling Pyran Formation in the Molybdenum Cofactor: Protonation of Quinoxalyl–Dithiolene Promoting Pyran Cyclization [PDF]

Inorganic Chemistry, 2019
Mononuclear Mo and W enzymes require a unique ligand known as molybdopterin (MPT). This ligand binds the metal through a dithiolene chelate, and the dithiolene bridges a reduced pyranopterin group. Pyran scission and formation have been proposed as a reaction of the MPT ligand that may occur within the enzymes to adjust reactivity at the Mo atom.
Douglas R. Gisewhite, Alexandra L. Nagelski, Daniel C. Cummins, Glenn P. A. Yap, Sharon J. N. Burgmayer   +4 more
openaire   +2 more sources

Nano-SiO2 catalyzed three-component preparations of pyrano[2,3-d]pyrimidines, 4H-chromenes, and dihydropyrano[3,2-c]chromenes

Journal of Saudi Chemical Society, 2018
An efficient one-pot three-component procedure has been developed for the preparation of tetrahydrobenzo[b]pyrans, dihydropyrano[3,2-c]chromenes, and pyrano[2,3-d]pyrimidines using nano-SiO2 as catalyst in H2O at 70 °C.
Ebrahim Mollashahi, Mohammad Nikraftar
doaj   +1 more source

Convenient One-Pot Synthesis of Spirooxindole-4H-pyrans in the Presence of SBA-Pr-NH2 and Evaluation of their Urease Inhibitory Activities [PDF]

Journal of Nanostructures, 2012
A simple and efficient one-pot three-component synthesis of the biologically important spirooxindole-4H-pyrans was carried out by the reaction of isatin, activated methylene reagents, and 4- hydroxycoumarin in aqueous medium. SBA-Pr-NH2 was found to be
G. Mohammadi Ziarani, N. Hosseini Mohtasham, N. Lashgari, A. Badiei, M. Amanlou, R. Bazl   +5 more
doaj   +1 more source

Cu-phthalocyanine Coated Hybrid Magnetic Nanoparticles: Preparation and Application in the Synthesis of Mono- and Bis pyrano[2,3-d]pyrimidinones and mono- and Bis-2-amino-4H-pyrans [PDF]

Iranian Journal of Chemistry & Chemical Engineering, 2020
In this research, Cu-phthalocyanine coated hybrid magnetic nanoparticles have been prepared in a simple method and evaluated as an efficient catalyst in the preparation of mono- and bis-pyrano[2,3-d]pyrimidinones and mono- and bis-2-amino-4H-pyrans from ...
Ali Reza Karimi, Fatemeh Bagherian, Marzie Karimi   +2 more
doaj   +1 more source

Synthesis of Polyfunctionalized 4H-Pyrans

Journal of Chemistry, 2013
Amberlyst A21 catalyzed one-pot three-component coupling of aldehyde and malononitrile with active methylene compounds such as acetylacetone and ethyl acetoacetate for the synthesis of pharmaceutically important polyfunctionalized 4H-pyrans has been ...
Manisha Bihani, Pranjal P. Bora, Ghanashyam Bez   +2 more
doaj   +1 more source

Synthesis of novel photochromic pyrans via palladium-mediated reactions

Beilstein Journal of Organic Chemistry, 2009
Photochromic pyrans for applications in material and life sciences were synthesized via palladium-mediated cyanation, carbonylation and Sonogashira cross-coupling starting from bromo-substituted naphthopyran 1 and benzopyrans 2a/b.
Christoph Böttcher, Gehad Zeyat, Saleh A. Ahmed, Elisabeth Irran, Thorben Cordes, Cord Elsner, Wolfgang Zinth, Karola Rueck-Braun   +7 more
doaj   +1 more source

Chiral Cyclopentadienyl Ruthenium Complexes as Versatile Catalysts for Enantioselective Transformations

CHIMIA, 2017
Ruthenium complexes, in particular cyclopentadienyl ruthenium (??) derivatives, catalyze a vast number of transformations in the field of homogenous catalysis.
David Kossler, Nicolai Cramer
doaj   +1 more source

Synthesis of Fe3O4@SiO2@Pr-NH2@DAP as a magnetic recyclable nano-catalyst for efficient synthesis of pyranothiazolopyrimidines and 4H-pyrans under solvent-free condition

Scientific Reports, 2023
In this research, we describe the synthesis of silica-coated nano-Fe3O4 particles, which were successfully modified by diaminopyrimidine, and their physicochemical properties were characterized using FT-IR, XRD, TEM, FE-SEM, EDX, EDX-mapping, and TGA ...
Maryam Danehchin, Abbas Ali Esmaeili
doaj   +1 more source

Synthesis of Pyran and Pyranone Natural Products [PDF]

Molecules, 2004
An overview of the synthesis of the fungal metabolites (+)-dermolactone, (–)- semixanthomegnin, (+)- and (–)-mellein, (–)-ochratoxin α, (–)-(1R,3S)-thysanone, the enantiopure ventiloquinones L, E and G, and 8-desmethyleleutherin from a common chiral intermediate, is presented. Further methodology leading potentially toward extended quinones such as (3S,
Christopher D. Donner, Melvyn Gill, Leonie M. Tewierik   +2 more
openaire   +4 more sources

Hydrochloric acid immobilized on nano‐titanium dioxide: a novel and efficient nanocatalyst for the synthesis of tetrahydrobenzo[b]pyrans [PDF]

شیمی کاربردی روز, 2017
Hydrochloric acid was immobilized onto the surface of amine functionalized nano‐titania. For this purpose, 2,4‐toluene diisocyanate (TDI) as a bi‐functional covalent linker was grafted onto a nano‐titania and next, the unreacted isocyanate groups were ...
Taiebeh Shamsi, Ali Amoozadeh, Elham Tabrizian   +2 more
doaj   +1 more source