Regioselective Monobromination of Free and Protected Phenols

Abstract

A comparative study of the advantages of using THF compared with DMF in regioselective monobromination reactions of highly activated polyphenols, their ethers, and their tert-butyl carbonate derivatives under mild conditions is described. Bromination with the common reagent N-bromosuccinimide in polar solvents provided an easy and fast approach to aromatic electrophilic substitution at the most elec-

Lamellarin D Bioconjugates I: Synthesis and Cellular Internalization of PEG-Derivatives

“…These compounds were obtained with good yields by borylation of the corresponding aryl bromides with pinacolborane using Pd(OAc) 2 and DPE-Phos as catalysts (for details, see Supporting Information). The protected alkoxy-aryl bromides required were obtained by protection of commercially available phenols followed by mild bromination via NBS in THF at -78 ºC (20).…”

Ion‐Pair‐Based Assemblies Comprising Pyrrole–Pyrazole Hybrids

“…4‐Bromo‐1,2,3‐trihexadecyloxybenzene : A mixture of K 2 CO 3 (6.11 g, 44.2 mmol), 4‐bromo‐1,2,3‐trihydroxybenzene20 (1.30 g, 6.32 mmol), and 1‐bromohexadecane (6.56 g, 21.5 mmol) in dry DMF (50 mL) was stirred at reflux for 3 days. After cooling, the solvent was evaporated.…”

“…Concentration of the appropriate fraction and recrystallization of the residue from CH 2 Cl 2 /MeOH gave 1 f as a pale-yellow solid (44.0 mg, 0.025 mmol, 77 %). R f = 0.43 (eluent: 1 % MeOH/CH 2 Cl 2 ); 1 H NMR (600 MHz, CDCl 3 , 208C; the pyrazole-NH signal could not be observed at this temperature because of fast proton exchange between the adjacent N atoms): d = 9.11 (br s, 2 H; pyrrole-NH), 6.70 (s, 4 4-Bromo-1,2,3-trihexadecyloxybenzene: A mixture of K 2 CO 3 (6.11 g, 44.2 mmol), 4-bromo-1,2,3-trihydroxybenzene [20] (1.30 g, 6.32 mmol), and 1-bromohexadecane (6.56 g, 21.5 mmol) in dry DMF (50 mL) was stirred at reflux for 3 days. After cooling, the solvent was evaporated.…”

Regioselective and High-Yielding Bromination of Phenols and Anilins Using N-Bromosaccharin and Amberlyst-15

“…Brominated arenes are extensively used as precursors in the preparation of various bioactive molecules, pharmaceuticals and play vital roles in the metal catalyzed coupling reactions. [1][2][3][4][5][6] A variety of brominating agents are available, 7 and recent reports describe the use of NBS-sulfonic acid functionalized silica, 8 NBS-Al 2 O 3 , 9 NBS-NH 4 OAc, 10 NBS-Pd(OAc) 2 , 11 NBS-DMF (or THF), 12 KBr-benzyltriphenyl phosphonium peroxy monosulfate and peroxodisulfate, 13,14 ZrBr 4 -diazene, 15 NBS-PTSA, 16 bromodichloroisocyanuric acid, 17 and N-methylpyrrolidin-2-one hydrotribromide-H 2 O 2 .…”