Presence Of N-bromosuccinimide Research Articles

Theoretical study of the oxidation of alcohols to the carbonyl compounds with N-bromosuccinimide and H 2O 2

Oxidation of both aliphatic and aromatic alcohols in the presence of N-bromosuccinimide and hydrogen peroxide under transition metal-free conditions has been studied by means of density functional theory (DFT) method. Solvent effect on the reaction is evaluated with the polarizable continuum model (PCM) and is compared with the experimental outcomes. In particular, the reaction mechanism is proposed and proved by theoretical study.

A New Alternative for the Synthesis of Highly Functionalized Phosphoryl Derivatives

Nucleophilic addition of diethylphosphite to Bayllis-Hillman acetate 5 in the presence of K2CO3 provides E and Z-allylphosphonates 6 , which could be converted in the presence of N-bromosuccinimide (NBS) and benzoyl peroxide as catalyst into allylbromides 2 . The primary one is further converted via an efficient tandem “formylation-hydrolysis” into the corresponding primary allylalcohol 8 . The secondary allylbromides 2 react with TEAF via a β -elimination to give buta-1,3-dienes 9 .

Preparation and Structure of Bicycloalkane-Condensed Aryldiaziridines Accompanied by Pyrimidines

Di-exo- and di-endo-2-aminonorbomane/enemethanamines 1-3, di-exo-oxanorbomene derivative 4 and cis-cyclohexane and trans-4-cyclohexene analogues 5, 6 were reacted with p-chlorobenzaldehyde in the presence of N-bromosuccinimide in dichloromethane. Via the reactions of 1-6, condensed diaziridines 7-12 accompanied by pyrimidine derivatives 13-16 were prepared after isolation with column chromatography. The mechanisms proposed for alternative transformations were supported by DFT calculations. The structures of the new compounds were proved by IR and NMR spectroscopy and, for 7, 9 and 12, also by means of X-ray crystallography.

Synthesis of Hexahydrofuro[2,3-b]furan and Hexahydrofuro[2,3-b]pyran Derivatives Starting from Baylis-Hillman Adducts via the Ueno-Stork Reaction

Fused polycyclic acetals are embodied in a wide range of natural products. Among bicyclic acetals, furofuran and furopyran derivatives are of special interest since both aliphatic and benzoannelated compounds of biological and pharmaceutical activity are known. Especially, the hexahydrofurofuran unit is present in many biologically active natural products. Some representative examples are communiol D, lupulin A, and asteltoxin as shown in Figure 1. During the investigation of radical cyclization of the suitably modified Baylis-Hillman adducts, we reasoned that we could synthesize a variety of furofuran and furopyran derivatives by following the Scheme 1. We reasoned that synthesis of bromoacetals from cinnamyl alcohols and 2,3dihydrofuran or 3,4-dihydro-2H-pyran and the following radical cyclization (Ueno-Stork reaction) would give the desired furofuran or furopyran derivatives. The use of cinnamyl alcohol derivative like 1a as the starting material would afford the furofuran or furopyran derivatives having the ester functionality at the 3-position, which could be functionalized for further transformations. The reaction of the cinnamyl alcohol 1a, which was prepared from the Baylis-Hillman adduct of benzaldehyde and methyl acrylate, and 3,4-dihydro-2H-pyran in the presence of NBS (N-bromosuccinimide) in acetonitrile at room temperature gave the desired bromoacetal 2a in moderate yield (74%). As reported, 2a was obtained as a trans isomer via the ring opening reaction of the intermediate bromonium ion. With bromoacetal 2a in our hand we tried radical cyclization (Ueno-Stork reaction) under the typical condition, n-Bu3SnH/AIBN in refluxing benzene. As expected, we could obtain the diastereomeric

Synthesis of Enantiopure Azetidines: A Route to New β‐Amino Alcohols.

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Stereoselective Synthesis of (E)‐β‐Arylvinyl Bromides by Microwave‐Induced Hunsdiecker‐Type Reaction.

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Stereoselective Synthesis of (E)-β-Arylvinyl Bromides by Microwave-Induced Hunsdiecker-Type Reaction

(E)-β-Arylvinyl bromides were readily prepared in a short reaction time (1-2 min) by microwave irradiation of the corresponding 3-arylpropenoic acids in the presence of N-bromosuccinimide and a catalytic amount of lithium acetate. Furthermore, two facile strategies for the efficient synthesis of (E)-β-bromo-4-arylethynylstyrene and (E)-β-bromo-4-arylstyrene have been developed by respectively combining Sonogashira and Suzuki coupling reaction with Hunsdiecker-type reaction. Formation of cis-α-bromo-β-lactone by microwave irradiation of cis-cinnamic acid with NBS provides a useful support for the mechanistic study of the present halodecarboxylation reaction.

Oxidation of the Methyl Group at the Aromatic Nucleus with Molecular Oxygen in the Presence of N‐Bromosuccinimide under Photoirradiation.

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A facile and sensitive spectrophotometric analysis of sulfonamides in pure form and its pharmaceuticals

A sensitive and simple spectrophotometric method for the determination of sulfonamides in either pure form or its pharmaceutical formulations is described. The method is based on the formation of red coloured product by the reaction of the sulfonamides with promethazine hydrochloride (PH) in presence of N-bromosuccinimide (NBS) in acidic medium. Beer's law is obeyed in the concentration range 0.1-15 μg ml - 1 at λ m a x 510 nm. The molar adsorptivity and Sandell's sensitivities are 10420.0-12630.0 dm 3 mol - 1 cm - 1 and 0.019-0.0236 μg cm - 2 , respectively.

Toward Synthesis of α‐Alkyl Amino Glycines (A3G), New Amino Acid Surrogates.

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Spectrophotometric Determination of Antiallergic Drug in Bulk Powder and in Its Pharmaceutical Formulations

Two simple, rapid and selective spectrophotometric methods have been described for the determination of promethazine hydrochloride (PMH) either in pure or pharmaceutical formulations. The methods are based on the formation of a green colored product with sulphanilic acid (SPA) in presence of N-bromosuccinimide (NBS) or a red colored, chloroform soluble product with p-nitroaniline (PNA) in presence of ceric ammonium sulphate (CAS). The chromogen formed has maximum absorption at 600 nm and at 510 nm with SPA and PNA, respectively. The optimum reaction conditions and other analytical parameters are evaluated. Beer's law is valid in the concentration range of 0.5–25 μg/mL (R= 0.9983) with SPA and 2–75 μg/mL (R = 0.9981) with PNA. Molar absorptivity values as calculated from the Beer's law data are 5.54 × 103 L/mol/cm and 3.05 × 103 L/mol/cm for SPA and PNA, respectively. The results are in good agreement with those of the official method. No interference was observed from common pharmaceutical excipients.

Oxidation of the Methyl Group at the Aromatic Nucleus with Molecular Oxygen­ in the Presence ofN-Bromosuccinimide under Photoirradiation

A methyl group at the aromatic nucleus can be oxidized to the corresponding carboxylic acid directly in the presence of N-bromosuccinimide (NBS) under photoirradiation. By considering both the promoting effect of oxygen and a catalytic amount of NBS, aerobic oxidation via hydroperoxide, which is thought to be generated by abstraction of a hydrogen with a bromo radical from NBS, proceeded.

Synthesis of gem‐Difluoroamines from Allylic or Halogenoamines.

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Toward synthesis of alpha-alkyl amino glycines (A3G), new amino acid surrogates.

A general method giving access to protected alpha-alkyl amino glycines (A3G) 4 from the previously described precursor alpha-isopropylthioglycine 1 is described. In the presence of N-bromosuccinimide, displacement of the thiol by a large variety of amines afforded the corresponding racemic amino acid mimics. The efficiency of the reaction was strongly dependent on the protective groups of the nucleophile used in the condensation.

Synthesis of gem-difluoroamines from allylic or halogenoamines

In HF–SbF 5, in the presence of N-bromosuccinimide, allylic or halogenoamines yield gem-difluoroamines, through bromofluorointermediates.

SOLID PHASE OLIGONUCLEOTIDE SYNTHESIS BY USING β-CE H-PHOSPHONATE APPROACH

ABSTRACT A new approach to the solid phase synthesis of oligonucleotide is described, which is based on oxidative coupling of nucleoside 3′-β-CE H-phosphonates in presence of N-Bromosuccinimide (NBS) as a coupling agent.

Synthesis of peracetylated d-galactopyranosylidene dihalides

Upon treatment with aluminium trichloride in absolute chloroform, β- d -galactopyranose penta- O -acetate was converted in high yield into tetra- O -acetyl-β- d -galactopyranosyl chloride. In the presence of N -bromosuccinimide in boiling carbon tetrachloride, homolytic substitution of the anomeric hydrogen atom in this β-chloride occurred selectively to afford tetra- O -acetyl-1-bromo-β- d -galactopyranosyl chloride, in admixture with minor amounts of tetra- O -acetyl- d -galactopyranosylidene chloride. Bromine substitution by fluorine took place with a low stereoselectivity in tetra- O -acetyl-1-bromo-β- d -galactopyranosyl chloride when treated with 1.25 equiv silver fluoride in acetonitrile, whereas tetra- O -acetyl- d -galactopyranosylidene fluoride could be prepared in 54 % yield with 3.3 equiv AgF. The gem -difluoride could be deacetylated quantitatively. Upon treatment with 1,4-diazabicyclo〚2.2.2〛octane, peracetylated 1-bromo-β- d -galactopyranosyl chloride underwent 1,2-elimination of hydrogen bromide to afford 2,3,4,6-tetra- O -acetyl- d - lyxo -hex-1-enopyranosyl chloride in 33 % yield. Le traitement du β- d -galactopyranose penta- O -acétylé par le trichlorure d’aluminium dans le chloroforme absolu conduit au chlorure de β- d -galactopyranosyle tétra- O -acétylé. Par bromuration radicalaire en présence de N -bromosuccinimide dans le tétrachlorure de carbone à reflux, le β-chlorure est converti en chlorure de 1-bromo-β- d -galactopyranosyle tétra- O -acétylé et en gem -dichlorure correspondant, produit mineur difficile à séparer. En présence de fluorure d’argent (1,25 equiv) dans l’acétonitrile, le chlorure de 1-bromo-β- d -galactopyranosyle acétylé donne un mélange des chlorofluorosucres correspondants. Avec 3,3 equiv d’AgF, le fluorure de d -galactopyranosylidène tétra- O -acétylé est obtenu avec un rendement de 54 %. La déacétylation de ce gem -difluorure est quantitative. Le chlorure de 1-bromo-β- d -galactopyranosyle tétra- O -acétylé subit, en présence de 1,4-diazabicyclo〚2.2.2〛octane, une élimination d’acide bromhydrique qui conduit au chlorure de 2,3,4,6-tétra- O -acétyl- d - lyxo -hex-1-ènopyranosyle, avec un rendement de 33 % seulement.

Synthesis and complexation properties of polystyrene supported polymeric thiacrown ether

Abstract A series of polystyrene supported thiacrown ethers were prepared from cross-linked chloromethylated polystyrene (CMPS). CMPS was etherified with propenol to form poly (4-propenyloxy methyl styrene) (PA), followed by the bromoalkoxylation of PA with chloroethanol (CE) in the presence of N-bromosuccinimide, and the etherification with w, w′-dimercaptopolyglycols. Their complexation capacity, selectivity and mechanism towards metal ions, especially precious metal ions, were also investigated. The polymeric thiacrown ethers possessed a high complexation capacity and selectivity for Ag+ and Au3+ then Pd2+, Pt4+, Hg2+, Cu2+, Zn2+, Mg2+ and K+. XPS revealed that both oxygen and sulfur atoms in the ring contributed to the coordination with metal ions.

Utility of diphenylamine and N-bromosuccinimide for colorimetric determination of certain phenothiazine drugs

A sensitive colorimetric method for the quantitative estimation of 11 phenothiazine drugs was developed. The method was based on the interaction of phenothiazine compounds with diphenylamine in presence of N-bromosuccinimide and sulfuric acid. Most of studied phenothiazines yielded bluish green products with two absorption maxima, one in the range of 392–396 nm with higher molar absorptivity and the other in the range of 770–780 nm with lower molar absorptivity. Phenothiazine base, mepazine HCl and pericyazine yielded blue products with only one maximum at 655, 775 and 778 nm, respectively. The color was stable for at least 1 h. The reproducibility and recovery of the method were excellent. The method was applied successfully to the determination of some commercially available phenothiazines in different dosage forms. Results were comparable to those obtained by official and reported methods.

Orthogonally Protected N-Methyl-Substituted α-Aminoglycines

Abstract: Title glycine derivatives FmocNRlCH(NR2Boc)CO2H (I; Fmoc =9-fluorenyl-methyloxycarbonyl; Boc = Me3CO2C; Rl = H, Me; R2 = H, Me), useful as templates for the introduction of desired functionalities into peptides, were prepared by condensation of glyoxylic acid and carbamates Fmoc-NH-Rl (Rl = H, Me), followed by conversion with Me2CHSH of the resulting FmocNRlCH(OH)CO2H to FmocNR1CH(SCHMe2)CO2H (Rl = H, Me) which were further treated with Boc-NH-R2 (R2 = H, Me) in the presence of N-bromosuccinimide. A simple and efficient synthesis of Fmoc-NH-Me and Boc-NH Me is also reported.