Categories: C-Br Bond Formation >
Synthesis of 1,2-dibromoalkanes
The combination of DMSO and oxalyl bromide is a highly efficient brominating reagent for various alkenes, alkynes and ketones. This bromination offers mild conditions, low cost, short reaction times, and provides dibromides and α-bromoketones in excellent yields.
R. Ding, J. Li, W. Jiao, M. Han, Y. Liu, H. Tian, B. Sun, Synthesis, 2018, 50, 4325-4335.
Tetrapropylammonium nonabromide (Pr4NBr9) is a solid reagent for rapid bromination reactions of various substrates. The reagent exhibits reactivity similar to that of elemental bromine, but shows higher selectivity and it is easier and safer to store and to handle.
T. M. Beck, H. Haller, J. Streuff, S. Riedel, Synthesis, 2014, 46, 740-747.
Organocatalytic stereospecific dibromination of various functionalized alkenes was achieved using a simple thiourea catalyst and 1,3-dibromo 5,5-dimethylhydantoin as a stable, inexpensive halogen source at room temperature. The procedure was extended to alkynes and aromatic rings and to dichlorination reactions by using the 1,3-dichloro hydantoin derivative.
G. Hernández-Torres, B. Tan, C. F. Barbas III, Org. Lett., 2012, 14, 1858-1861.
Bromination of alkenes, alkynes, and anilines has efficiently been carried out at room temperature in short reaction times using potassium bromide and orthoperiodic acid in dichloromethane-water (1:1) to prepare the corresponding brominated compounds with excellent yields.
A. Khazaei, M. A. Zolfigol, E. Kolvari, N. Koukabia, H. Soltania, F. Komakia, Synthesis, 2009, 3672-3676.
In an oxidative bromination of alkenes to 1,2-dibromo alkanes with HBr, dimethyl sulfoxide serves as the oxidant as well as cosolvent. Whereas simple olefins are brominated in very good yields, three of six styrene derivatives yielded bromohydrins under the reaction conditions.
M. Karki, J. Magolan, J. Org. Chem., 2015, 80, 3701-3707.
In bromination of alkenes by dibromine and dealkylation of aromatic ethers by boron tribromide, a fluorous phase acts as a liquid membrane permitting passive transport of the reagents at the bottom to the top layer involving the substrates, thereby regulating the reactions.
I. Ryu, H. Matsubara, S. Yasuda, H. Nakamura, D. P. Curran, J. Am. Chem. Soc., 2002, 124, 12946-12947.
A Ph3P/I--promoted dihalogenation of epoxides provides 1,2-dihalides in the presence of XCH2CH2X (X = Cl or Br) as the solvent and halogen source. All reagents are widely available and easy to handle. The protocol offers mild conditions and operational simplicity.
J. Long, J. Chen, R. Li, Z. Liu, X. Xiao, J.-H. Ling, X. Zheng, J.-C. Xiao, Synlett, 2019, 30, 181-184.
An efficient two-step protocol that employs readily available terminal alkenes as starting materials enables a highly regio- and stereoselective synthesis of various allylic acetates. This method affords linear (E)-isomers and tolerates several functional groups including halogen-containing molecules. For other weak oxygen, carbon, nitrogen, and sulfur nucleophiles, adducts were obtained in very good yields too.
X. Huang, B. Fulton, K. White, A. Bugarin, Org. Lett., 2015, 17, 2594-2597.
Unsaturated compounds such as alkenes, alkynes, allenes, and methylenecyclopropanes (MCPs) can be dibrominated within minutes by NBS and lithium bromide in THF at room temperature in good to excellent yields under mild conditions.
L.-X. Shao, M. Shi, Synlett, 2006, 1269-1271.
In an efficient one-pot method for the syntheses of di- and polybrominated esters from readily available aldehydes starting with a Wittig reaction, the in situ generated byproduct PPh3O mediates a subsequent bromination with oxalyl bromide and greatly improves the efficiency of the cascade reaction.
T.-Y. Hu, H. Wei, Y.-C. Luo, Y. Wang, Z.-Y. Wang, P.-F. Xu, J. Org. Chem., 2016, 81, 2730-2736.
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.
An efficient method allows the construction of 2,6-cis-4,5-dibromo-tetrasubstituted tetrahydropyran rings with well-controlled stereochemistry in good yields.
F. Liu, T.-P. Loh, Org. Lett., 2007, 9, 2063-2066.
The use of NaSO2CF3 and NaBrO3 enables a free-radical bromotrifluoromethylation of olefins. Sodium bromate acts not only as a single-electron oxidant but also as a bromine source.
Z.-Q. Liu, D. Liu, J. Org. Chem., 2017, 82, 1649-1656.