Oxalyl Bromide Research Articles

Halogenation of arenes with sulfoxide and oxalyl halide

The utilization of DMSO or Ph2SO/(COBr)2 or (COCl)2 for the bromination or chlorination of arenes has been explored. Notably, monobromination of activated arenes can be achieved with high regioselectivity using the combination of dimethyl sulfoxide and oxalyl bromide. Bromodimethylsulfonium bromide generated in situ was proposed to be the active species for bromination. In contrast, the practicality of chlorination of arenes with DMSO or Ph2SO/(COCl)2 is limited due to production of the formation of by-products such as aryldimethylsulfonium chlorides or dichlorinated arenes.

The Dynamics of Br Formation from the Primary and Secondary C–Br Bond Dissociation of Oxalyl Bromide near 265 and 234 nm

The Dynamics of Br Formation from the Primary and Secondary C–Br Bond Dissociation of Oxalyl Bromide near 265 and 234 nm

A facile synthesis of γ-butenolides via cyclization of 3-alkenoic acids with dimethyl sulfoxide and oxalyl bromide

The combination of dimethyl sulfoxide and oxalyl bromide was used to accomplish the cyclization of 3-alkenoic acids with the aid of a base to afford γ-butenolides, in which bromodimethylsulfonium salt generated in situ was proposed to serve as a Br+ source.

A Highly Efficient Method for the Bromination of Alkenes, Alkynes and Ketones Using Dimethyl Sulfoxide and Oxalyl Bromide

The pairing of DMSO and oxalyl bromide is reported as a highly efficient brominating reagent for various alkenes, alkynes and ketones. This bromination approach demonstrates remarkable advantages, such as mild conditions, low cost, short reaction times, provides excellent yields in most cases and represents a very attractive alternative for the preparation of dibromides and α-bromoketones.

Reagent-Controlled Synthesis of the Branched Trisaccharide Fragment of the Antibiotic Saccharomicin B.

A concise synthesis of a branched trisaccharide, α-l-Dig-(1 → 3)-[α-l-Eva-(1 → 4)]-β-d-Fuc, corresponding to saccharomicin B, has been developed via reagent-controlled α-selective glycosylations. Starting from the d-fucose acceptor, l- epi-vancosamine was selectively installed using 2,3-bis(2,3,4-trimethoxyphenyl)cyclopropene-1-thione/oxalyl bromide mediated dehydrative glycosylation. Following deprotection, l-digitoxose was installed using the AgPF6/TTBP thioether-activation method to produce the trisaccharide as a single α-anomer. This highly functionalized trisaccharide can potentially serve as both a donor and an acceptor for the total synthesis of the antibiotic saccharomicin B.

Evaluation and optimization of synthetic routes from dihydroartemisinin to the alkylamino-artemisinins artemiside and artemisone: A test of N-glycosylation methodologies on a lipophilic peroxide

10-Alkylamino-artemisinins including artemiside and artemisone display enhanced activities against malaria. Earlier, dihydroartemisinin (DHA) TMS ether was converted by trimethylsilyl bromide into the 10-β-bromide that with amine nucleophiles provided the amino-artemisinins. In an attempt to develop more economic approaches, direct N-glycosylation of DHA was examined but 2-deoxyartemisinin was invariably obtained. However, hydroxyl group activation by conversion into the 10β-halide in non-polar solvents with anhydrous HCl and Group I and II metal halides, oxalyl chloride or thionyl chloride with catalytic DMSO, and oxalyl bromide did succeed. The β-halides were converted in situ by thiomorpholine into artemiside, and by thiomorpholine-1,1-dioxide into artemisone respectively in scalable reactions. Hydrogen peroxide-acetonitrile or the urea-hydrogen peroxide complex efficiently oxidized the sulfide artemiside to the sulfone artemisone. Overall, a generalized approach to 10-alkylamino-artemisinins is now available.

Reagent-Controlled α-Selective Dehydrative Glycosylation of 2,6-Dideoxy- and 2,3,6-Trideoxy Sugars.

We have found that activating either 2,3-bis(2,3,4-trimethoxyphenyl)cyclopropenone or 2,3-bis(2,3,4-trimethoxyphenyl)cyclopropene-1-thione with oxalyl bromide results in the formation of a species that promotes the glycosylation between 2,6-dideoxy-sugar hemiacetals and glycosyl acceptors in good yield and high α-selectivity. Both reactions are mild and tolerate a number of sensitive functional groups including highly acid-labile 2,3,6-trideoxy-sugar linkages.

Reagent‐Controlled α‐Selective Dehydrative Glycosylation of 2,6‐Dideoxy‐ and 2,3,6‐Trideoxy Sugars

AbstractWe have found that activating either 2,3‐bis(2,3,4‐trimethoxyphenyl)cyclopropenone or 2,3‐bis(2,3,4‐trimethoxyphenyl)cyclopropene‐1‐thione with oxalyl bromide results in the formation of a species that promotes the glycosylation between 2,6‐dideoxy‐sugar hemiacetals and glycosyl acceptors in good yield and high α‐selectivity. Both reactions are mild and tolerate a number of sensitive functional groups including highly acid‐labile 2,3,6‐trideoxy‐sugar linkages.

ChemInform Abstract: Triphenylphosphine Oxide‐Catalyzed Stereoselective Poly‐ and Dibromination of Unsaturated Compounds.

AbstractThe Ph3PO‐catalyzed reaction of α,β‐unsaturated esters (I) and β,γ‐unsaturated α‐ketoesters (VII) with oxalyl bromide affords trans‐dibromides (II) and (VIII), resp., with good to high diastereoselectivity.

Ruthenium(II)‐Catalyzed Protocol for Preparation of Diverse α,β‐ and β,β‐Dihaloenones from Diazodicarbonyls

AbstractEfficient one‐step syntheses of α,β‐ and β,β‐dihaloenones were achieved by ruthenium(II)‐catalyzed reactions between cyclic or acyclic diazodicarbonyl compounds and oxalyl chloride or oxalyl bromide in moderate to good yields. This methodology offers several significant advantages, which include ease of handling, mild reaction conditions, one‐step reaction, and the use of an effective and non‐toxic catalyst. The synthesized compounds were further transformed into highly functionalized novel molecules bearing aromatic rings on the enone moiety using the Suzuki reaction.magnified image

Rasta resin-triphenylphosphine oxides and their use as recyclable heterogeneous reagent precursors in halogenation reactions.

Heterogeneous polymer-supported triphenylphosphine oxides based on the rasta resin architecture have been synthesized, and applied as reagent precursors in a wide range of halogenation reactions. The rasta resin–triphenylphosphine oxides were reacted with either oxalyl chloride or oxalyl bromide to form the corresponding halophosphonium salts, and these in turn were reacted with alcohols, aldehydes, aziridines and epoxides to form halogenated products in high yields after simple purification. The polymer-supported triphenylphosphine oxides formed as a byproduct during these reactions could be recovered and reused numerous times with no appreciable decrease in reactivity.

ChemInform Abstract: A New Synthesis of Five‐Membered Heterocyclic Quorum Sensing Inhibitors.

AbstractThe reaction of heterocycles (I) and (IV) with oxalyl bromide is examined to yield E/Z‐mixtures of the title compounds after cleavage of the ‐O‐Me bond.

A new synthesis of five-membered heterocyclic quorum sensing inhibitors

5-(Bromoalkylidene)furan-2(5H)-ones, thiophen-2(5H)-ones, and pyrrol-2(5H)-ones are prepared in good yields by cleavage of the corresponding 2-acyl-5-methoxy heterocycles using oxalyl bromide in dichloromethane at ambient temperature.

Vibronic spectra, ab initio calculations, and structures of conformationally non-rigid molecules of oxalyl halides in the ground and lowest excited electronic states – Part VI: Oxalyl bromide (COBr) 2 and summary

The structure of oxalyl bromide (COBr) 2 in the ground and four lowest excited electronic states was theoretically investigated using the CASPT2/cc-pVTZ-DK method. Structural information obtained allowed the reassignment of the A ˜ 1 A u ← X ˜ 1 A g and a ˜ 3 A u ← X ˜ 1 A g vibronic absorption spectra. Generalization of oxalyl halide structural data for the ground and excited electronic states is presented.

ChemInform Abstract: A General Synthesis of 3,5-Dihalo-2H-1,4-oxazin-2-ones from Cyanohydrins.

In a novel approach starting from O-trimethylsilyl protected or unprotected cyanohydrins and oxalyl chloride or bromide, a series of unkown 6-substituted 3,5-dihalo-2H,1,4-oxazin-2-ones were prepared. The method was shown to be efficient for various types of cyanohydrins; however cyclization was not obtained with cyanohydrins containing bulky substituents, electron-rich aryl or heteroaryl groups. A mechanism is proposed.

Tandem Oxidation/Halogenation of Aryl Allylic Alcohols under Moffatt−Swern Conditions

Aryl allylic alcohols are converted to halogenated unsaturated ketones or allylic halides using excess Moffatt-Swern reagent. Electron-poor aromatic rings favor formation of the halogenated ketone, while electron-donating substituents in the ortho or para positions favor formation of the allylic halide. The oxidation/halogenation reaction performs well with both oxalyl chloride and oxalyl bromide, providing access to the corresponding chlorides or bromides, respectively.

Observation of dihalide elimination upon electron attachment to oxalyl chloride and oxalyl bromide, 300–550K

Rate coefficients have been measured for electron attachment to oxalyl chloride [ClC(O)C(O)Cl] and oxalyl bromide [BrC(O)C(O)Br] in He gas at 133 Pa pressure over the temperature range of 300-550 K. With oxalyl chloride, the major ion product of attachment is Cl2(-) at all temperatures (66% at 300 K); its importance increases slightly as temperature increases. Two other product ions formed are Cl- (18% at 300 K) and the phosgene anion CCl2O- (16% at 300 K) and appear to arise from a common mechanism. With oxalyl bromide, the Br2(-) channel represents almost half of the ion product of attachment, independent of temperature. Br- accounts for the remainder. For oxalyl chloride, the attachment rate coefficient is small [(1.8 +/- 0.5) x 10(-8) cm3 s(-1) at 300 K], and increases with temperature. The attachment rate coefficient for oxalyl bromide [(1.3 +/- 0.4) x 10(-7) cm3 s(-1) at 300 K] is nearly collisional and increases only slightly with temperature. Stable parent anions C2Cl2O2(-) and C2Br2O2(-) and adduct anions Cl- (C2Cl2O2) and Br- (C2Br3O2) were observed but are not primary attachment products. G2 and G3 theories were applied to determine geometries of products and energetics of the electron attachment and ion-molecule reactions studied. Electron attachment to both oxalyl halide molecules leads to a shorter C-C bond and longer C-Cl bond in the anions formed. Trans and gauche conformers of the neutral and anionic oxalyl halide species have similar energies and are more stable than the cis conformer, which lies 100-200 meV higher in energy. For C2Cl2O2, C2Cl2O2(-), and C2Br2O2(-), the trans conformer is the most stable conformation. The calculations are ambiguous as to the oxalyl bromide geometry (trans or gauche), the result depending on the theoretical method and basis set. The cis conformers for C2Cl2O2 and C2Br2O2 are transition states. In contrast, the cis conformers of the anionic oxalyl halide molecules are stable, lying 131 meV above trans-C2Cl2O2(-) and 179 meV above trans-C2Br2O2(-). Chien et al. [J. Phys. Chem. A 103, 7918 (1999)] and Kim et al. [J. Chem. Phys. 122, 234313 (2005)] found that the potential energy surface for rotation about the C-C bond in C2Cl2O2 is "extremely flat." Our computational data indicate that the analogous torsional surfaces for C2Br2O2, C2Cl2O2(-), and C2Br2O2(-) are similarly flat. The electron affinity of oxalyl chloride, oxalyl bromide, and phosgene were calculated to be 1.91 eV (G3), and 2.00 eV (G2), and 1.17 eV (G3), respectively.

Molecular structures of gauche and anti conformers for oxalyl bromide: ab initio and DFT calculations

The molecular structure and conformational nature of oxalyl bromide are investigated by the ab initio and DFT methods. Both the MP2 and B3LYP optimized structures are better consistent with the experimental result in the gas phase. The CC bond torsional angle of the gauche conformation is quite sensitive to the choice of the calculational level. The B3LYP potential energy surface around the anti conformation is so flat that the existence of the anti conformation is not certain. It is suggested that the geometry calculations at the MP2 level can explain the nature of conformation in oxalyl bromide better than those at the B3LYP level.

Carben- und Carbin-Komplexe des Technetiums und Rheniums - Synthese, Struktur und Reaktionen / Carbene and Carbyne Complexes of Technetium and Rhenium - Synthesis, Structure and Reactions

Abstract Synthesis, structure and reactions of technetium and rhenium complexes bearing metal-carbon multiple bonds are reported. Addition of LiPh to Cp*M (CO)3 (1a : M = Tc; 1b: M = Re) (Cp* = η5-C5Me5) in Et2O yields the acyl complexes Li[Cp*(CO)2MC(O)Ph]·Et2O (2a: M = Tc; 2 b: M = Re). These are converted with Et3OBF4 into the carbene complexes Cp*(CO)2M = C(OEt)Ph (3a, 3b). Reaction of 3a and 3 b with BCl3 affords the carbyne complexes [Cp*(CO)2M ≡ CPh]BCl4 (4a, 4b) in high yield. The acyl complex 2b can be directly converted into the carbyne complex [Cp*(CO)2Re ≡ CPh]Br (5b), when it is treated with oxalyl bromide. Nucleophiles add at the carbynecarbon atoms of 4a and 4b, as demonstrated by the reaction with NaOCy (Cy = cyclohexyl) to afford the carbene complexes Cp*(CO)2M = C(OCy)Ph (6a, 6b). Similarly, reaction of P(OMe)3 with [Cp*(CO)2Re ≡ CPh]Cl (5b'), the latter being generated in situ from 2b and oxalyl chloride, gives the ylide complex {Cp*(CO)2Re = C[P(OMe)3]Ph}Cl (7b'). In comparison, addition of P(OMe)3 to [Cp*(CO)2Tc ≡ CPh]Cl (5a'), generated in situ from 2a and oxalyl chloride, induces a carbvne-carbonvl coupling reaction resulting in the formation of the ketenyl complex . Thermolysis of the compounds 2a, 2b, 4a, 4b and 7b' has been studied in vacuo and the products of decomposition identified by IR spectroscopy. The solid-state structure of the carbene complexes 3 a and 3 b was determined by single crystal X-ray diffraction studies. Both compounds crystallize in the monoclinic space group P21/n with very similar unit cell data. Striking feature of the isostructural carbene complexes is the nearly perpendicular orientation of the carbene ligand relative to the Cp* ring.

Syntheses, reactivities and molecular structures of tungsten complexes containing the diphenylphosphinodithioformato ligand

Treatment of [NEt4][W(CO)5(PPh2)]1 with CS2 afforded [NEt4][W(CO)5(PPh2CS2)]3 which was also synthesized from the reaction of [W(CO)5(MeCN)] with [NEt4][PPh2CS2]2. The reactions of 3 with various alkyl halides gave the neutral complexes [W(CO)5{PPh2(CS2R)}][R = Me(4a), Et, C2H4OH, C3H5, CH2CN, C2H4CN or C3H6CN], and the reactions of 3 with acyl halides gave [W(CO)5{PPh2(CS2COR)}](R = Me or Ph). Both alkylation and acylation reactions occur at the sulfur atom. Treatment of 3 with [Re(CO)5Br] afforded [(OC)5W(µ-PPh2CS2)Re(CO)5] in which the two metal atoms were bridged by the PPh2CS2– ligand. The reaction of 3 with [W(pip)2(CO)4](pip = piperidine) yielded [W(CO)5(PPh2H)] and the dithiocarbamato tungsten complex [NEt4][W(CO)4(S2CNC5H10)]. Complex 3 reacted with organic α,ω-diiodides (CH2I2, C2H4I2, C3H6I2), giving the phosphine bridged dinuclear complexes [{W(CO)5(PPh2CS2)}2(µ-CH2)n](n= 1–3), and only in the reaction of C3H6I2, was a mononuclear complex {[W(CO)5{PPh2(CS2C3H6I)}]} seen as a minor product. Complex [{W(CO)5(PPh2CS2)}2(CO)2] was obtained from the reaction of 3 with oxalyl bromide in CH2Cl2. Thermolysis of 3 in tetrahydrofuran (thf) gave an anionic product identified as [NEt4][W(CO)4(PPh2CS2)]. All of the complexes were identified by spectroscopic methods. The structures of complexes 2, 3, and 4a were confirmed by single-crystal X-ray diffraction analyses. Crystal data: 2, monoclinic, space group P21, a= 10.244(4), b= 9.877(4), c= 11.124(3)A, β= 102.02(2)°, Z= 2, R= 0.062, R′= 0.073 based on 1180 reflections with l > 2σ(l); 3, triclinic, space group P, a= 10.688(3), b= 11.070(2), c= 12.785(2)A, α= 88.26(1), β= 81.87(2), γ= 74.081(17)°, Z= 2, R= 0.028, R′= 0.025 based on 4557 reflections with l > 2σ(l); 4a, triclinic, space group P, a= 9.177(5), b= 9.403(3), c= 12.461(6)A, α= 90.00(3), β= 103.85(4), γ= 94.79(3)°, Z= 2, R= 0.041, R′= 0.041 based on 2442 reflections with l > 2σ(l).