40774-41-2Relevant articles and documents
Solvent free, light induced 1,2-bromine shift reaction of α-bromo ketones
An, Sejin,Moon, Da Yoon,Park, Bong Ser
, p. 6922 - 6928 (2018/10/24)
Photolysis of α-bromopropiophenones in acetonitrile results in formation of β-bromopropiophenones with good product selectivity, which can be coined as 1,2-Br shift reaction. The product selectivity increases when the reaction is done in neat or solid state, where only the 1,2-Br shift product is formed in some cases. The reaction is suggested to proceed by C–Br bond homolysis to give a radical pair, followed by disproportionation and conjugate addition of HBr to the α,β-unsaturated ketone intermediate. When the unsaturated intermediate is stabilized by an extra conjugation, the reaction stops at the stage, in which the unsaturated ketone becomes a major product. The synthetic method described in this research fits in a category of eco-friendly organic synthesis nicely since the reaction does not use volatile organic solvents and any other additives such as acid, base or metal catalysts, etc. Besides, the method fits into perfect atom economy, which does not give any side products. The synthetic method should find much advantage over other alternative methods to obtain β-bromo carbonyl compounds.
A scalable procedure for light-induced benzylic brominations in continuous flow
Cantillo, David,De Frutos, Oscar,Rincon, Juan A.,Mateos, Carlos,Oliver Kappe
supporting information, p. 223 - 229 (2014/01/17)
A continuous-flow protocol for the bromination of benzylic compounds with N-bromosuccinimide (NBS) is presented. The radical reactions were activated with a readily available household compact fluorescent lamp (CFL) using a simple flow reactor design based on transparent fluorinated ethylene polymer (FEP) tubing. All of the reactions were carried out using acetonitrile as the solvent, thus avoiding hazardous chlorinated solvents such as CCl4. For each substrate, only 1.05 equiv of NBS was necessary to fully transform the benzylic starting material into the corresponding bromide. The general character of the procedure was demonstrated by brominating a diverse set of 19 substrates containing different functional groups. Good to excellent isolated yields were obtained in all cases. The novel flow protocol can be readily scaled to multigram quantities by operating the reactor for longer time periods (throughput 30 mmol h-1), which is not easily possible in batch photochemical reactors. The bromination protocol can also be performed with equal efficiency in a larger flow reactor utilizing a more powerful lamp. For the bromination of phenylacetone as a model, a productivity of 180 mmol h -1 for the desired bromide was achieved.
Environmentally benign electrophilic and radical bromination 'on water': H2O2-HBr system versus N-bromosuccinimide
Podgor?ek, Ajda,Stavber, Stojan,Zupan, Marko,Iskra, Jernej
experimental part, p. 4429 - 4439 (2009/10/09)
A H2O2-HBr system and N-bromosuccinimide in an aqueous medium were used as a 'green' approach to electrophilic and radical bromination. Several activated and less activated aromatic molecules, phenylsubstituted ketones and styrene were efficiently brominated 'on water' using both systems at ambient temperature and without an added metal or acid catalyst, whereas various non-activated toluenes were functionalized at the benzyl position in the presence of visible light as a radical activator. A comparison of reactivity and selectivity of both brominating systems reveals the H2O2-HBr system to be more reactive than NBS for benzyl bromination and for the bromination of ketones, while for electrophilic aromatic substitution of methoxy-substituted tetralone it was higher for NBS. Also, higher yields of brominated aromatics were observed when using H2O2-HBr 'on water'. Bromination of styrene reveals that not just the structure of the brominating reagent but the reaction conditions: amount of water, organic solvent, stirring rate and interface structure, play a key role in defining the outcome of bromination (dibromination vs bromohydroxylation). In addition, mild reaction conditions, a straightforward isolation procedure, inexpensive reagents and a lower environment impact make aqueous brominating methods a possible alternative to other reported brominating protocols.
A new amino-masking group capable of pH-triggered amino-drug release
Gilmer, John F.,Simplicio, Ana Luisa,Clancy, John M.
, p. 315 - 323 (2007/10/03)
The prodrug approach is potentially useful for mitigating pharmaceutical problems - such as poor membrane permeability or stability - which commonly occur with amino drugs. On the other hand there persists a dearth of useful systems for masking amines tha
PHOTOCHEMISTRY OF α-HALOCYCLOALKANONES AND α,α-DIHALOCYCLOALKANONES. IONIC AND RADICAL PHOTOCHEMICAL CARBON-HALOGEN BOND CLEAVAGE
Sket, Boris,Zupan, Marko
, p. 1745 - 1752 (2007/10/02)
The nature of the photochemical carbon-halogen bond cleavage in α-halo cycloalkanones depends on the halogen atom bonded and on the ring size of the cycloalkanone.In the 2-halo-1-indanone series the amount of radical products increased from iodine to chlorine, while in the case of 2-halo-3,4-dihydro-1(2H)-naphthalenone 43percent for iodo, 32percent for bromo, and 53percent for the chloro derivative were found.On the other hand, photochemical carbon-chlorine bond cleavage in 2,2-dichloro-1-indanone led to only radical products, while the formation of both radical and ionic products inthe ratio 1:1 was observed in the case of 2,2-dibromo-1-indanone.In the 2,2-dihalo-3,4-dihydro-1(2H)-naphthalenone series, the ratio of the radical to ionic products formed strongly depended on the halogen atom bonded: preferential formation of the radical product in the case of the chloro derivative (92percent) in contrast to 94percent of the ionic products in the case of the bromoderivative, was observed.
