Bromination of Alkynes in Ionic Liquids − A Kinetic Investigation

Abstract

The kinetic behaviour and the product distributions of brominations of several arylalkynes with Br 2 in the room-temperature ionic liquids (ILs) 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF 6 ] and 1-butyl-3-methylimidazolium bromide [bmim]Br, have been investigated at different temperatures. In [bmim]Br, alkynes stereospecifically gave the anti addition products, the reactions following a secondorder rate law. In [bmim] [PF 6 ], mixtures of syn and anti addition products were obtained, and the reactions followed a second-or third-order rate law, depending on the structure of the alkyne and the concentration of Br 2 . The data obtained for the reactions in [bmim]Br are interpreted on the basis of a mechanism involving a product-and a rate-determining nucleophilic attack by bromide on the alkyne−Br 2 π complex. The data relating to the electrophilic addition in [bmim] [PF 6 ]

Promoting effect of ionic liquids on ligand substitution reactions

“…Although ILs have been applied to a wide range of catalytic reactions, there have been relatively few careful studies regarding the effects of these solvents on reaction rate, mechanism, or selectivity [28][29][30][31][32]. Studies of complex multi-step catalytic processes can provide some information about overall solvent effects, but a more thorough understanding of these properties requires looking at solvent effects on individual reaction steps.…”

Ionic liquids: a versatile medium for palladium-catalyzed reactions

“…52,132,133 The possibility of working in the absence of ligand was evaluated. The Stille coupling of aryl iodide with vinyl and alkyl stannanes were performed in various ionic liquids (Scheme 29), which have different physico-chemical properties according to the nature of the anion and cation.…”

Novel electrophilic aromatic iodine substitution of some naphtholic Schiff bases

“…Iodination of aromatic compounds was carried out by using molecular iodine together with Lewis acid or a strong oxidizing agent such as Ag 2 SO 4 , NaIO 4 , HIO 4 , NaOCl, liquid SO 3 , iodic acid, 3 nitric acid and sulfuric acid, 4 sulfur trioxide and hydrogen peroxide. [5][6][7][8][9] Recently, direct iodination methods have been reported using various iodinium donating reagents, such as iodine/Na 2 NaOCl-NaI, 12 bis(pyridineiodonium(I)tetrafluoroborate-CF 3 SO 3 H, 13 iodine silver sulfate, 14 NIS-CF 3 SO 3 H, 2 iodine-mercury salts, 15 iodine monochloride, 16 mercury(II)-oxide-iodine, 17 bis(symcollidine)iodine(I)hexafluorophosphate, 18 iodine-di-iodine pentoxide, 19 NIS (N-iodosuccinimide), 20 iodine-nitrogendioxide, 21 iodine-F-TEDA-BF 4,22 iodine-iodic acid, 23 n-BuLi-CF 3 CH 2 I, 24 NH 4 I-oxone, 25 ICl. 26 However, most of these methods require a high reaction temperature and long reaction times, 20 work in low yields, 27 involve toxic heavy metals, involve harsh conditions, and generate costly or complex and hazardous waste.…”