Search results for "CLEAVAGE"
showing 10 items of 281 documents
ChemInform Abstract: Metal-Free Regioselective C-C Bond Cleavage in 1,3,5-Triazine Derivatives of β-Diketones.
2014
The reaction of cyanuric chloride (I) with 3 equivalents of ketones (II) in the presence of 3 equivalents of KOH affords adducts (IV), which are converted into deacylated derivatives (III) by treatment with aqueous HCl solution in MeOH.
ChemInform Abstract: Multi-Arm 1,2,3-Thiadiazole Systems.
2010
Benzene derivatives 2a–c with 6, 4, and 3 side chains bearing terminal 1,2,3-thiadiazole rings, respectively, have been prepared. Alkaline cleavage of 2a–c led to the corresponding alkynethiolates 6a–c, which were trapped by electrophiles such as benzyl bromide or iodomethane. The method provides an alternative to the thermal or photochemical cleavage of 1,2,3-thiadiazoles to thioketenes, which react further with nucleophiles.
Photodissociation of Formyl Fluoride in Rare Gas Matrixes
2006
Photodissociation of formyl fluoride (HCOF) is studied in Ar, Kr, and Xe matrixes at 248 and 193 nm excitation by following spectral changes in the infrared absorption spectra. In all matrixes, the main photodissociation products are CO/HF species, including CO-HF and OC-HF complexes and thermally unstable CO/HF species (a distorted CO/HF complex or a reaction intermediate), which indicate negligible cage exit of atoms produced via the C-F and C-H bond cleavage channels. However, the observation of traces of H, F, CO, CO(2), F(2)CO, FCO, and HRg(2)(+) (Rg = Kr or Xe) in Kr and Xe matrixes would imply some importance of other reaction channels too. The analysis of the decay curves of the pre…
Alkylumlagerungen und acidolyse der ethylidenbrücken bei der synthese von ethylidendiphenolen
1990
For the synthesis of symmetrical and unsymmetrical ethylidenediphenols the corresponding hydroxyphenylethanols (1a–c) were prepared by hydrogenation of hydroxyphenyl methyl ketones with hydrogen/Raney nickle or with lithium aluminium hydride. Condensations of the hydroxyphenylethanols with different phenols under the usual acidic conditions gave products formally resulting form transalkylations. Only the reaction of 1-(3-bromo-2-hydroxy-5-methylphenyl)ethanol (1c) with p-cresol gave the expected product 2d with 82% yield. Experiments with ethylidenediphenols showed that with acids in presence or absence of phenols cleavage and recondensations take place leading to products of formal transal…
ChemInform Abstract: Cyclocondensation of 6-Acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine with Hydroxylamine and Hydrazine.
2010
The cyclocondensation of 6-acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine (3) with hydroxylamine or hydrazine leads to 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenylisoxazolo-[5,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4a) and 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenyl-1H-pyrazolo[3,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4b), respectively. In the presence of methanolic hydrogen chloride, 4b undergoes a cleavage of the pyrimidine ring to yield (5-amino-1,2,4-triazol-1-yl)(3,5-dimethylpyrazol-4-yl)phenylmethane (5). The structure determination of the compounds obtained is based on 1H and 13C nmr spectra including NOE measurements.
Cyclocondensation of 6-acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine with hydroxylamine and hydrazine
1998
The cyclocondensation of 6-acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine (3) with hydroxylamine or hydrazine leads to 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenylisoxazolo-[5,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4a) and 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenyl-1H-pyrazolo[3,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4b), respectively. In the presence of methanolic hydrogen chloride, 4b undergoes a cleavage of the pyrimidine ring to yield (5-amino-1,2,4-triazol-1-yl)(3,5-dimethylpyrazol-4-yl)phenylmethane (5). The structure determination of the compounds obtained is based on 1H and 13C nmr spectra including NOE measurements.
Better understanding of the ring-cleavage process of cyanocyclopropyl anionic derivatives. A theoretical study based on the electron localization fun…
2005
[reaction: see text] Theoretical calculations at the B3LYP/6-31+G(d), MP2/6-31+G(d), and G3(MP2) levels have been carried out to understand the alternative reaction pathways (the cyclopropyl ring cleavage (RC) and the retrocycloaddition reaction (rCA)) of a constrained tricyanocyclopropyl anionic derivative. The more energetically favorable path is found to be the RC process, a formally "forbidden" rearrangement (Leiviers, M.; Tam, I.; Groves, K.; Leung, D.; Xie, Y.; Breslow, R. Org. Lett. 2003, 5, 19, 3407) yielding an allylic anion system via a concerted transition structure, in agreement with experimental outcomes. rCA is more energetically favorable along a two-stage mechanism, via an i…
Multi-Arm 1,2,3-Thiadiazole Systems
1997
Benzene derivatives 2a–c with 6, 4, and 3 side chains bearing terminal 1,2,3-thiadiazole rings, respectively, have been prepared. Alkaline cleavage of 2a–c led to the corresponding alkynethiolates 6a–c, which were trapped by electrophiles such as benzyl bromide or iodomethane. The method provides an alternative to the thermal or photochemical cleavage of 1,2,3-thiadiazoles to thioketenes, which react further with nucleophiles.
A Photochemical One-Pot Three-Component Synthesis of Tetrasubstituted Imidazoles
2014
Tetrasubstituted imidazoles can be formed in a photochemical one-pot synthesis from aldehydes, α-aminonitriles, and isoxazoles. Condensation of the first two components produces α-(alkylideneamino)nitriles which react under basic conditions with the acylazirines formed in situ by photochemical ring transformation of the isoxazole component. This process includes an unusual cleavage of the C(2)-C(3) bond of the acylazirine. The reaction mechanism was studied by DFT calculations.
Über die photosensibilisierte autoxydation von polyvinylalkohol
1968
Polyvinylalkohol wurde in wasriger Losung bei 30°C unter Belichtung mit einer Quecksilberhochdrucklampe einer mit benzophenn-3.3′-disulfonsaurem Natrium photosensibilisierten Autoxydation unterworfen. Als Reaktionsprodukte wurden Wasserstoffperoxid, Sauren und Kohlendioxid ermittelt. Unter den gewahlten Reaktionsbedingungen werden die Makromolekule statistisch abgebaut. Viskositatsmessungen und analytische Bestimmungen zeigen, das pro Spaltung der polymerkette nur eine Carboxylendgruppe entsteht. Ein Reaktionsmechanismus wird diskutiert. Polyvinylalcohol was oxidized in water solution at 30°C by irradiation with a mercury high pressure lamp and benzophenon-3.3′-disodiumdisulfonate as sensit…