Synthesis of Multibromo-Substituted Quinolines by NBS-Mediated Cascade Electrophilic Bromination/Cyclization of N-(3-Phenylprop-2-ynyl)anilines

A new and convenient protocol is presented here for the synthesis of 3,6,8-tribromoquinolines via cascade cyclization of N-(3-phenylprop-2-ynyl)anilines employing N-bromosuccinimide as an electrophile. The metal-free process is carried out under mild conditions and is compatible with a variety of substituents. The Sonogashira coupling reaction regioselectively occurs at position C-6 of the obtained products.

Electrophilic Bromination in Flow: A Safe and Sustainable Alternative to the Use of Molecular Bromine in Batch

Bromination reactions are crucial in today’s chemical industry since the versatility of the formed organobromides makes them suitable building blocks for numerous syntheses. However, the use of the toxic and highly reactive molecular bromine (Br2) makes these brominations very challenging and hazardous. We describe here a safe and straightforward protocol for bromination in continuous flow. The hazardous Br2 or KOBr is generated in situ by reacting an oxidant (NaOCl) with HBr or KBr, respectively, which is directly coupled to the bromination reaction and a quench of residual bromine. This protocol was demonstrated by polybrominating both alkenes and aromatic substrates in a wide variety of solvents, with yields ranging from 78% to 99%. The protocol can easily be adapted for the bromination of other substrates in an academic and industrial environment.

Practical, mild and efficient electrophilic bromination of phenols by a new I(iii)-based reagent: the PIDA–AlBr3system

A practical electrophilic bromination procedure for the phenolic core was developed under efficient and very mild reaction conditions. The new I(iii)-based brominating reagentPhIOAcBroperationally easy to prepare by mixing PIDA and AlBr3was used.

Sixfold Peripheral Halogenation of Tribenzotriquinacenes: An Alternative Access to Useful TBTQ Building Blocks

Sixfold electrophilic bromination and iodination of the molecular periphery of the bridgehead-tetramethylated tribenzotriquinac­ene (TBTQ) with N-bromosuccinimide (NBS) and N-iodosuccinimide (NIS), respectively, under various conditions was studied to develop an alternative preparative approach to the classical Lewis acid catalyzed bromination. Running these reactions in trifluoroacetic acid either in pure form or with chloroform as a co-solvent at elevated temperatures, or under sonication or microwave irradiation was found to give increasingly fast and efficient conversion of TBTQ to the target hexahalogenated TBTQ derivatives in excellent yields. NIS was found to be markedly more reactive than NBS, whereas N-chlorosuccimide reacted hardly. The new method was applied to the sixfold functionalization of the 4b,8b,12b-tripropyl-12d-methyl-TBTQ analogue to give the corresponding hexabromo and hexaiodo derivatives. Some sixfold C–C cross-coupling reactions of hexahalo derivatives of TBTQ were carried out in excellent yields to enlarge the three spatially orthogonal indane wings of the TBTQ core.

Bifunctional organocatalysts for the asymmetric synthesis of axially chiral benzamides

Bifunctional organocatalysts bearing amino and urea functional groups in a chiral molecular skeleton were applied to the enantioselective synthesis of axially chiral benzamides via aromatic electrophilic bromination. The results demonstrate the versatility of bifunctional organocatalysts for the enantioselective construction of axially chiral compounds. Moderate to good enantioselectivities were afforded with a range of benzamide substrates. Mechanistic investigations were also carried out.

[PhSiO1.5]8,10,12as nanoreactors for non-enzymatic introduction of ortho, meta or para-hydroxyl groups to aromatic molecules

Traditional electrophilic bromination follows long established “rules”: electron-withdrawing substituents cause bromination selective formetapositions, whereas electron-donating substituents favororthoandparabromination.

New insights into bromination process: effective preparation of Ambroxol

Ambroxol used as an expectorant in treating respiratory diseases was effectively prepared with a total yield of 62 %, with o-toluidine as the feedstock via successive procedures of electrophilic bromination, acetylation, radical benzylic bromination, N-alkylation and hydrolysis processes. The addition of aqueous hydrogen peroxide could enhance the utilisation of liquid bromine in the electrophilic bromination of o-toluidine, avoiding the hazardous HBr generated as a by-product. In addition, liquid bromine promoted by MnO