Categories: C-Br Bond Formation >
Synthesis of bromohydrins
Highly regioselective ring opening of epoxides to halohydrins has been carried out in impressive yields with hydrogen and lithium halides in presence of β-cyclodextrin using water as solvent.
M. Arjun Reddy, K. Surendra, N. Bhanumathi, K. Rama Rao, Tetrahedron, 2002, 58, 6003-6008.
The use of trihaloisocyanuric acid/triphenylphosphine enables a regioselective conversion of epoxides to vicinal chloro-/bromohydrins and vicinal dihalides under mild and neutral conditions in acetonitrile. The reactions proceed smoothly in high yield at room temperature and at reflux, respectively, over a short time.
V. S. C. de Andrade, M. C. S. de Mattos, Synthesis, 2016, 48, 1381-1388.
A very rapid and efficient method has been developed for the synthesis of vicinal bromohydrins and alkoxybromides directly from olefins without any catalyst using N,N-dibromo-p-toluenesulfonamide (TsNBr2) as the brominating agent in CH3CN-water or alcohol.
P. Phukan, P. Chakraborty, D. Kataki, J. Org. Chem., 2006, 71, 7533-7537.
A zwitterion-catalyzed intermolecular bromoesterification of alkenes works with acid and olefin in an equimolar ratio. Mechanistic study revealed that the charge pair in the zwitterion works synergistically in activating both NBS and carboxylic acid.
W.-H. Ng, R.-B. Hu, Y.-P. Lam, Y.-Y. Yeung, Org. Lett., 2020, 22, 5567-5571.
Electrochemical technology enables alkene alkoxyhalogenation and organohalide dehalogenation in one pot. Anodic conversion of the C=C bond to radical cation intermediates and cathodic transformations of organohalides run in parallel.
T.-T. Zhang, M.-J. Luo, Y. Li, R.-J. Song, J.-H. Li, Org. Lett., 2020, 22, 7230-7233.
The reaction of tribromoisocyanuric acid with alkenes in the presence of nucleophilic solvents (various alcohols, acetic acid, and H2O in acetone) led to the corresponding β-bromoethers, β-bromoacetates and bromohydrins in high regioselectivity and good yields.
L. S. de Almeida, P. M. Esteves, M. C. S. de Mattos, Synlett, 2006, 1515-1518.
A green, oxidant-free electrochemical method enables radical bromination, chlorination and trifluoromethylation-formyloxylation of various alkenes with readily available halogen radical (NaCl, NaBr), and trifluoromethyl radical (CF3SO2Na) sources in DMF as formyloxylation reagent in an undivided electrochemical cell.
X. Sun, H.-X. Ma, T.-S. Mei, P. Fang, Y. Hu, Org. Lett., 2019, 21, 3167-3171.
Oxidative bromination of different types of olefins using Selectfluor/KBr afforded addition, monobromo-substituted, or Hunsdiecker-Borodin reaction products in good yields.
C. Ye, J. M. Shreeve, J. Org. Chem., 2004, 69, 8561-8563.