86428-68-4Relevant academic research and scientific papers
COMPARISON OF SYN DEHYDROHALOGENATIONS FROM TANS-1-BROMO-2-CHLOROCYCLOALKENES PROMOTED BY COMPLEX BASE AND BY POTASSIUM TERT-BUTOXIDE
Croft, Alan P.,Bartsch, Richard A.
, p. 2737 - 2740 (1983)
Compared with t-BuOK-t-BuOH, syn eliminations from trans-1-bromo-2-chlorocycloalkanes (C4-C8) induced by NaNH2-NaO-t-Bu in THF are rapid, exhibit greater propensity for dehydrochlorination and show little sensitivity to ring size of the dihalocycloalkane.
Flash vacuum pyrolysis over magnesium. Part 1 - Pyrolysis of benzylic, other aryl/alkyl and aliphatic halides
Aitken, R. Alan,Hodgson, Philip K.G.,Morrison, John J.,Oyewale, Adebayo O.
, p. 402 - 415 (2007/10/03)
Flash vacuum pyrolysis over a bed of freshly sublimed magnesium on glass wool results in efficient coupling of benzyl halides to give the corresponding bibenzyls. Where an ortho halogen substituent is present further dehalogenation gives some dihydroanthracene and anthracene. Efficient coupling is also observed for halomethylnaphthalenes and halodiphenylmethanes while chlorotriphenylmethane gives 4,4′-bis(diphenylmethyl)biphenyl. By using α,α′-dihalo-o-xylenes, benzocyclobutenes are obtained in good yield, while the isomeric α,α′-dihalo-p-xylenes give a range of high thermal stability polymers by polymerisation of the initially formed p-xylylenes. Other haloalkylbenzenes undergo largely dehydrohalogenation where this is possible, in some cases resulting in cyclisation. Deoxygenation is also observed with haloalkyl phenyl ketones to give phenylalkynes as well as other products. With simple alkyl halides there is efficient elimination of HCl or HBr to give alkenes. For aliphatic dihalides this also occurs to give dienes but there is also cyclisation to give cycloalkanes and dehalogenation with hydrogen atom transfer to give alkenes in some cases. For 5-bromopent-1-ene the products are those expected from a radical pathway but for 6-bromohex-1-ene they are clearly not. For 2,2-dichloropropane and 1,1-dichloropropane elimination of HCl occurs but for 1,1-dichlorobutane, -pentane and -hexane partial hydrolysis followed by elimination of HCl gives E, E-, E,Z- and Z,Z- isomers of the dialk-1-enyl ethers and fully assigned 13C NMR data are presented for these. With 6-chlorohex-1-yne and 7-chlorohept-1-yne there is cyclisation to give methylenecycloalkanes and -cycloalkynes. The behaviour of 1,2-dibromocyclohexane and 1,2-dichlorocyclooctane under these conditions is also examined. Various pieces of evidence are presented that suggest that these processes do not involve generation of free gas-phase radicals but rather surface-adsorbed organometallic species.
ALKENE EPOXIDATIONS CATALYSED BY CHEMICALLY ROBUST Mn(III) PORPHYRINS AND PROMOTED BY HOCl UNDER AQUEOUS-ORGANIC TWO-PHASE CONDITIONS IN THE ABSENCE OF AXIAL LIGAND AND PHASE-TRANSFER CATALYST: REACTION MECHANISM AND LARGE-SCALE PREPARATIVE APPLICATIONS
Banfi, Stefano,Dragoni, Massimo,Montanari, Fernando,Pozzi, Gianluca,Quici, Silvio
, p. 431 - 436 (2007/10/02)
Under CH2Cl2/H2O two-phase conditions alkene epoxidations, catalysed by Mn(III)-porphyrins and promoted by aqueous NaOCl adjusted at pH 10.0 with NaHCO3, proceed in the absence of a phase-transfer catalyst and, for electron-rich olefins, also in the absence of axial ligands.Under these conditions, reliable kinetic measurements on cyclooctene epoxidation can be obtained by using the chemically robust Mn(III)-tetra(2,6-dichlorophenyl)porphyrin chloride, as the side reactions associated with the oxidative demoliton of the axial ligand and of the quaternary onium salts donot occur.The results indicate that reactions follow Michaelis-Menten saturation kinetics which are confirmed by the oxidation rates of different substrates in competitive epoxidations.The absence of strong axial ligands, like pyridine or imidazole bases, highlights the autocatalytic behaviour of the reactions, probably because the produced epoxides act as weak axial ligands.Indeed, reactions are noticeably accelerated by initial addition of consistent amounts of epoxides.Under the conditions reported here electron-rich olefins can be oxidised on a large scale, the overall catalyst turnovers being in the range 30,000-100,000 in 20-24 h at 20 deg C.
