7159-94-6Relevant articles and documents
Electrophotocatalytic C?H Heterofunctionalization of Arenes
Huang, He,Lambert, Tristan H.
supporting information, p. 11163 - 11167 (2021/04/19)
The electrophotocatalytic heterofunctionalization of arenes is described. Using 2,3-dichloro-5,6-dicyanoquinone (DDQ) under a mild electrochemical potential with visible-light irradiation, arenes undergo oxidant-free hydroxylation, alkoxylation, and amination with high chemoselectivity. In addition to batch reactions, an electrophotocatalytic recirculating flow process is demonstrated, enabling the conversion of benzene to phenol on a gram scale.
Teaching Old Compounds New Tricks: DDQ-Photocatalyzed C?H Amination of Arenes with Carbamates, Urea, and N-Heterocycles
Das, Somnath,Natarajan, Palani,K?nig, Burkhard
supporting information, p. 18161 - 18165 (2017/12/28)
The C?H amination of benzene derivatives was achieved using DDQ as photocatalyst and BocNH2 as the amine source under aerobic conditions and visible light irradiation. Electron-deficient and electron-rich benzenes react as substrates with moderate to good product yields. The amine scope of the reaction comprises Boc-amine, carbamates, pyrazoles, sulfonimides and urea. Preliminary mechanistic investigations indicate arene oxidation by the triplet of DDQ to radical cations with different electrophilicity and a charge transfer complex between the amine and DDQ as intermediate of the reaction.
Kinetics and mechanism of hydrolysis of phenylureas
Salvestrini, Stefano,Di Cerbo, Paola,Capasso, Sante
, p. 1889 - 1893 (2007/10/03)
The hydrolysis of phenylureas has been found to be affected by temperature, pH and buffer concentration. Kinetic evidence suggests that the formation of phenylisocyanate, the initial product in the title reaction, occurs via an intermediate zwitterion. Depending on pH and buffer concentrations, the zwitterion can be produced through three parallel routes: at low pH, specific acid-general base catalysis, followed by slow deprotonation of a nitrogen atom by a general base; at high pH, specific basic-general acid catalysis, followed by slow protonation of a N atom by a general acid; at intermediate pH the reaction proceeds through a proton switch promoted by buffers. Bifunctional acid-base buffers such as HCO3-/CO32-, H2PO42- and CH3COOH/CH3COO- are very efficient catalysts. At high buffer concentration, as well as at pH 12, the breakdown of the zwitterion is rate-determining. The results are discussed in relation to recently published papers reporting different pathways.
A novel synthesis of isocyanates and ureas via β-elimination of haloform
Braverman,Cherkinsky,Kedrova,Reiselman
, p. 3235 - 3238 (2007/10/03)
A novel synthesis of isocyanates via base-induced β-elimination of haloform from N-monosubstituted trihaloacetamides is described. The rate of reaction exhibits a strong dependence on the nature of the trihalomethyl group. Thus, while the reaction of tribromoacetamides proceeds at room temperature and the reaction of trichloroacetamides requires heating in polar solvents, no reaction could be observed for any of the corresponding trifluoro derivatives. This novel β-elimination of haloform from stable and readily available trihaloacetamides was applied to a 'one-pot' synthesis of ureas which avoids the use of phosgene and isolation of isocyanates.
