Electrophilic Bromine Source Research Articles

Fluorination of α-diazo-γ-lactams with the Olah reagent

A series of N-aryl α-fluoro-γ-lactams were successfully prepared by hydrofluorination of diazo counterparts with the Olah reagent in moderate yields. This approach was also applied to bromofluorination with N-bromosuccinimide as electrophilic bromine source.

Widely Exploited, Yet Unreported: Regiocontrolled Synthesis and the Suzuki–Miyaura Reactions of Bromooxazole Building Blocks

An approach to synthesis of 2‐, 4‐, and 5‐bromooxazoles is described. The method was optimized, and its scope was extended to all three isomeric parents, as well as various alkyl‐ and aryl‐substituted bromooxazoles. It was found that direct regiocontrolled lithiation followed by reaction with electrophilic bromine source was common for all substrates and led exclusively to the target substituted 2‐, 4‐ and 5‐bromooxazoles on multigram scale. The utility of the multipurpose building blocks obtained in this work was demonstrated in the Suzuki–Miyaura cross‐coupling reaction under parallel synthesis conditions.

Catalytic Asymmetric Bromocyclization of Polyenes.

The first catalytic asymmetric bromonium ion-induced polyene cyclization has been achieved by using a chiral BINOL-derived thiophosphoramide catalyst and 1,3-dibromo-5,5-dimethylhydantoin as an electrophilic bromine source. Bromocyclization products are obtained in high yields, with good enantiomeric ratios and high diastereoselectivity, and are abundantly found as scaffolds in natural products.

ChemInform Abstract: A Metal‐Free Protocol for Aminofunctionalization of Olefins Using TsNBr2.

N,N-Dibromo-p-toluene sulfonamide (TsNBr2) has been found to be an effective reagent for various aminofunctionalization reactions. This reagent behaves both as an electrophilic bromine source as well as amine to react with olefins under different conditions to yield aminoether, imidazoline, diamine and amino bromine. The reaction proceeds rapidly under mild conditions with high regioselectivity. Olefins react with TsNBr2 in moist THF to form δ-amino ether at room temperature. Treatment of TsNBr2 with olefin in MeCN at room temperature produced imidazoline in high yield. Further modification of the reaction condition resulted in the development of a one-step procedure for the synthesis of N-acetyl,N′-tosyl diamine derivatives directly from olefin. When the olefin was treated with 2.4 mol equiv of TsNBr2 in the presence of K2CO3, N,N′-ditosyl diamine derivative was obtained in moderate yield. Instantaneous formation of aminobromine was observed when an olefin was treated with the reagent in dry CH2Cl2 at ro...

ChemInform Abstract: N,N‐Dibromo‐p‐toluenesulfonamide (TsNBr2): A Promising Alternative Bromo‐Organic Reagent

AbstractReview: [57 refs.

A Metal-Free Protocol for Aminofunctionalization of Olefins Using TsNBr2.

N,N-Dibromo-p-toluene sulfonamide (TsNBr2) has been found to be an effective reagent for various aminofunctionalization reactions. This reagent behaves both as an electrophilic bromine source as well as amine to react with olefins under different conditions to yield aminoether, imidazoline, diamine and amino bromine. The reaction proceeds rapidly under mild conditions with high regioselectivity. Olefins react with TsNBr2 in moist THF to form δ-amino ether at room temperature. Treatment of TsNBr2 with olefin in MeCN at room temperature produced imidazoline in high yield. Further modification of the reaction condition resulted in the development of a one-step procedure for the synthesis of N-acetyl,N'-tosyl diamine derivatives directly from olefin. When the olefin was treated with 2.4 mol equiv of TsNBr2 in the presence of K2CO3, N,N'-ditosyl diamine derivative was obtained in moderate yield. Instantaneous formation of aminobromine was observed when an olefin was treated with the reagent in dry CH2Cl2 at room temperature.

N,N-Dibromo-p-Toluenesulfonamide (TsNBr2): A Promising Alternative Bromo-Organic Reagent

<i>N</i>,<i>N</i>-Dihalosulfonamides are important reagents for various organic transformations. Simplicity, efficiency, and a unique chemical behaviour make this class of compounds synthetically useful. <i>N</i>,<i>N</i>-Dibromo-<i>p</i>-toluenesulfonamide (TsNBr₂) is an efficient source of electrophilic bromine, which, at the same time, also provides the nucleophilic sulfonamide counterpart to form a C–N bond. This reagent has also been found to be a suitable precursor of nitrene. These diverse properties led to the development of various important organic transformations under catalyst-free and relatively mild reaction conditions. However, the strong oxidizing nature of this reagent sometimes appears as a limitation for a desired functional group transformation. 1 Introduction 2 Cohalogenation of Olefins 3 Activation of Alkynes with TsNBr₂ 4 Oxidation Reactions 5 Nitrene Transfer Reactions 6 Hofmann Rearrangement Using TsNBr₂ 7 Bromination of Aromatic Compounds 8 Cleavage of Oximes 9 Miscellaneous Reactions 10 Conclusion

Synthetic pathway for a new series of liquid crystal 2,6-disubstituted imidazo[2,1-b][1,3,4]thiadiazole

Herein, the synthesis of a novel series of liquid crystals 2,6-disubstituted imidazo[2,1-b]-1,3,4-thiadiazoles derivate is reported. These fused heterocyclic compounds were prepared through the cyclodehydration between 5-substituted-1,3,4-thiadiazole-2-amino derivatives and α-bromo aryl ketones. The derivates of 2-amino-thiadiazole were obtained from the condensation reaction between thiosemicarbazide and aryl/alkyl nitriles with good yields (60–83%). The α-bromination of aryl ketones was carried out using NBS as the source of electrophilic bromine, also with good yields (52–85%). For the final compounds, the liquid crystal behaviour was shown to be dependent on the number of chains. Mesomorphism was not observed for compounds without aliphatic chains, with more than two aliphatic chains or when the aliphatic chains are methoxy groups.

Gold(i)-catalyzed enantioselective bromocyclization reactions of allenes

The enantioselective bromocyclization of allenes is accomplished through the use of a chiral dinuclear gold complex and/or chiral phosphate anions in the presence of an N-bromolactam as an electrophilic bromine source. This method provides access to heterocyclic vinyl bromides with an allylic stereocenter in excellent yield and enantioselectivity. These enantioenriched vinyl bromides may serve as a handle for further derivatization via cross-coupling reactions.

Tribromoisocyanuric Acid (TBCA)

This paper provides a description of tribromoisocyanuric acid (TBCA), a new reagent used as a source of electrophilic bromine (Br+) in organic synthesis, including in Green Chemistry procedures. Its applications embrace the bromination of alkenes, β-dicarbonyl compounds and deactivated arenes, as well as oxidations of urazoles, bisurazoles, and thiols.

Amidines as potent nucleophilic organocatalysts for the transfer of electrophilic bromine from N-bromosuccinimide to alkenes

(±)- iso-Amarine is a potent organocatalyst at 1 mol % loading for both the bromoacetoxylation of alkenes with added acetic acid and bromolactonisation of unsaturated carboxylic acids with stoichiometric NBS as the electrophilic bromine source. A simple bromoamidine with an N–Br bond has been characterised crystallographically for the first time. Asymmetric induction in the bromination reactions with enantiopure amidines was zero.

Oxidative Cyclization of Thiobenzanilides to Benzothiazoles Using N‐Benzyl‐DABCO Tribromide under Mild Conditions.

N-benzyl-DABCO tribromide, a stable, crystalline organic ammonium tribromide (OATB), have been used as an alternative electrophilic bromine source for the efficient oxidative cyclization of thiobenzanilides to the corresponding benzothiazoles under mild conditions.

Oxidative Cyclization of Thiobenzanilides to Benzothiazoles Using N-Benzyl-DABCO Tribromide under Mild Conditions

N-benzyl-DABCO tribromide, a stable, crystalline organic ammonium tribromide (OATB), have been used as an alternative electrophilic bromine source for the efficient oxidative cyclization of thiobenzanilides to the corresponding benzothiazoles under mild conditions.

Synthesis of functionalized 1-azaspirocyclic cyclopentanones using bronsted acid or N-bromosuccinimide promoted ring expansions.

Azaspirocyclic ring systems are present in a variety of alkaloids. Functionalized 1-azaspirocyclopentanones (6, 7, 11, 12) can be efficiently constructed through semipinacol ring expansion reactions of 2-(1-hydroxycyclobutyl)-p-toluenesulfonylenamides (4) promoted by either a Bronsted acid ((S)-(+)-10-camphorsulfonic acid or HCl) or N-bromosuccinimide, an electrophilic bromine source. Reactions promoted by N-bromosuccinimide tend to proceed in higher yields (80-95%) and with greater diastereoselectivity (3:1-1:0) compared to those reactions promoted by a Bronsted acid. In addition, N-bromosuccinimide promoted reactions can produce a complementary stereochemical outcome compared to the reactions using Bronsted acid.

Efficient Conversion of Substituted Aryl Thioureas to 2‐Aminobenzothiazoles Using Benzyltrimethylammonium Tribromide.

The reaction of molecular bromine (Br2) with arylthioureas is known to produce 2-aminobenzothiazoles (Hugerschoff reaction). We show here that benzyltrimethylammonium tribromide (1, PhCH2NMe3Br3), a stable, crystalline organic ammonium tribromide (OATB), can be readily utilized as an alternative electrophilic bromine source. It is easier to control the stoichiometry of addition with an OATB, which minimizes aromatic bromination caused by excess reagent. We have developed a direct procedure from isothiocyanates and amines using tetrabutylammonium thiocyanate (Bu4NSCN) and PhCH2NMe3Br3 to afford functionalized 2-aminobenzothiazoles.

Efficient conversion of substituted aryl thioureas to 2-aminobenzothiazoles using benzyltrimethylammonium tribromide.

The reaction of molecular bromine (Br2) with arylthioureas is known to produce 2-aminobenzothiazoles (Hugerschoff reaction). We show here that benzyltrimethylammonium tribromide (1, PhCH2NMe3Br3), a stable, crystalline organic ammonium tribromide (OATB), can be readily utilized as an alternative electrophilic bromine source. It is easier to control the stoichiometry of addition with an OATB, which minimizes aromatic bromination caused by excess reagent. We have developed a direct procedure from isothiocyanates and amines using tetrabutylammonium thiocyanate (Bu4NSCN) and PhCH2NMe3Br3 to afford functionalized 2-aminobenzothiazoles.

A New Approach to the Reduction of Sulfoxides to Sulfides with 1,3‐Dithiane in the Presence of Electrophilic Bromine as Catalyst.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A new approach to the reduction of sulfoxides to sulfides with 1,3-dithiane in the presence of electrophilic bromine as catalyst.

A new, mild, and novel method is described for the efficient deoxygenation of sulfoxides to their corresponding sulfides with 1,3-dithiane at room temperature in the presence of catalytic amounts of N-bromosuccinimide (NBS), 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TABCO), or Br(2) as the source of electrophilic bromine.

Organic bromine as a source of electrophilic bromine in aqueous chlorination reactions

Aqueous HOCl displaces p-bromo substituents from phenol and aniline nuclei to produce an electrophilic species capable of brominating some aromatic compounds.

1-Bromo- and 1-iodo-benzotriazoles

1-Bromo- and 1-iodo-benzotriazoles are obtained from 1-chlorobenzotriazole and bromine and iodine respectively. The bromo-compound is a reactive oxidant and source of electrophilic bromine. Pentachlorobenzotriazole is more reactive than 1-chlorobenzotriazole in accord with its greater positive halogen character.