Nucleophilic Addition Of Methanol Research Articles

Photocatalytic nucleophilic addition of alcohols to styrenes in Markovnikov and anti-Markovnikov orientation.

The nucleophilic addition of methanol and other alcohols to 1,1-diphenylethylene (1) and styrene (6) into the Markovnikov- and anti-Markovnikov-type products was selectively achieved with 1-(N,N-dimethylamino)pyrene (Py) and 1,7-dicyanoperylene-3,4:9,10-tetracarboxylic acid bisimide (PDI) as photoredox catalysts. The regioselectivity was controlled by the photocatalyst. For the reductive mode towards the Markovnikov-type regioselectivity, Py was applied as photocatalyst and triethylamine as electron shuttle. This approach was also used for intramolecular additions. For the oxidative mode towards the anti-Markovnikov-type regioselectivety, PDI was applied together with Ph–SH as additive. Photocatalytic additions of a variety of alcohols gave the corresponding products in good to excellent yields. The proposed photocatalytic electron transfer mechanism was supported by detection of the PDI radical anion as key intermediate and by comparison of two intramolecular reactions with different electron density. Representative mesoflow reactor experiments allowed to significantly shorten the irradiation times and to use sunlight as “green” light source.

Eco-friendly kinetic separation of trans-limonene and carvomenthene oxides

Kinetic separation of trans-limonene oxide and trans-carvomenthene oxide was achieved in high yield by selective ring opening of their cis-epoxides in the presence of InCl3 catalyst in water. Catalytic activity of InCl3 was conserved up to 10 cycles. Nucleophilic addition of methanol in presence of InCl3 was also selective as cis-epoxides preferentially reacted leaving behind trans-epoxides, which were separated by fractional distillation. The kinetic separation of trans-limonene oxide and trans-carvomenthene oxide was achieved in high yield (97%) by selective ring opening of the corresponding cis-oxides in a reaction of 1:1 mixture of these epoxides with water or methanol in the presence of InCl3 catalyst.

Nucleophilic addition of methanol and methanethiol to acetylene in the superbasic system KOH-DMSO: a quantum chemical model

Cluster-continuum models (KOH·nDMSO, n = 1, 5) were used to model the superbasic system “alkali metal hydroxide-dimethyl sulfoxide” within the framework of MP2/6-311++G**/ and B3LYP/6-31G* methods. The KOH molecule surrounded by five DMSO molecules exists as “solvate-loosened” ion pair with elongated K-O distance. It is proposed to consider the “solvate-loosened” ion pair of potassium cation with hydroxide anion in the surroundings of five solvent molecules as the catalytic coordination sphere of the superbasic system KOH-DMSO. Methanol and methanethiol molecules can be incorporated with ease into the first coordination sphere of potassium cation to form methoxide and methanethiolate ions. The possibility of nucleophilic attack of methoxide and methanethiolate ions on acetylene molecule in the first coordination sphere of potassium cation was studied. The model reaction system C2H2-CH3OK-H2O with one DMSO molecule included explicitly to maintain the “solvate-loosened” [CH3O]−...K+ ion pair and additional inclusion of solvent effects within the framework of the IEFPCM continuum model is the most preferable for serial calculations.

In situ ligand formation in the synthesis of an octanuclear dysprosium ‘double cubane’ cluster displaying single molecule magnet features

The nucleophilic addition of methanol and water to the dicyanonitrosomethanide anion, resulting in the formation of cyano(imino(methoxy)methyl)nitrosomethanide (cmnm) and carbamoylcyanonitrosomethanide (ccnm), respectively, is used as a means of in situ ligand synthesis during the formation of [Dy(8)(OH)(6)(OMe)(6)(cmnm)(10)(ccnm)(2)(H(2)O)(2)(MeOH)(2)] (1). This is the first time these reactions have been observed to be promoted by the presence of a lanthanoid ion. The core of the octanuclear cluster consists of two cubane moieties ([Dy(4)(OH)(3)(OMe)]), bridged by four methoxide ligands to form a central [Dy(8)(OH)(6)(OMe)(6)] moiety. The complex displays magnetic properties that are indicative of probable single molecule magnet features.

2-Polyfluoroalkyl thiopyrylium salts: synthesis and reactions with nucleophiles

2-Polyfluoroalkylthiopyrylium salts have been synthesized by oxidative aromatization of 2-polyfluoroalkyl-2 H-thiopyrans with triphenylmethane tetrafluoroborate. Nucleophilic addition of methanol, sodium azide, or urea to 2-trifluoromethylthiopyrylium tetrafluoroborate in a basic medium proceeds at the α-position to give the corresponding 2-substituted 6-trifluoromethyl-2 H-thiopyrans whereas imidazoles, fluorine-containing 1,2,3-triazole, potassium thiolacetate, and sodium nitromethane afford mixtures of 2 H- and 4 H-thiopyrans. cis-Dihydroxylation of 6-trifluoromethyl-2-methoxy-2 H-thiopyran affords the fluorine-containing thiohexenopyranoside derivative 8.

Catalyst concentration effect on the hydroesterification and hydroformylation-acetalization of 1-hexene by a rh complex

The complex, [Rh(COD)(4-picoline)2](PF6) (COD = 1,5-cyclooctadiene), immobilized on poly(4-vinylpyridine) in contact with methanol catalyzes the hydroesterification and hydroformylation-acetalization of 1-hexene to methylheptanoate, heptanal and 1,1-dimethoxyheptane, respectively. The by-product, 1,1-dimethoxyheptane comes from the nucleophilic addition of methanol over the heptanal formed. Also, H2 and CO2 from the water gas shift reaction (WGSR) are observed. The catalytic activity for the hydroformylation and the WGSR proved to be non-linear in the rhodium total concentration range 0.9-5.0 wt.%.

Complexes with New Chelate Anionic Ligands Formed by Nucleophilic Addition in Copper(II) Coordination Sphere. III. The Crystal Structures of (2,2'-Bipyridine-N,N')(cyanato-N)[methyl(2-cyano-2-imidoxy Ethaneimidate-N,N')]copper(II) and (2,2'-Bipyridine-N,N')(2-cyano-2-imidoxy Ethaneimidate-N,N')copper(II)

Crystal structures of Cu(II) compounds with new chelate anionic ligands are presented. The formulae of these compounds are [Cu(bipy)(mcoe)(NCO)] (1) and [Cu(bipy)(coe)] (2), where bipy is 2,2'-bipyridine, mcoe and coe are the anionic chelate ligands methyl(2-cyano-2-imidoxy ethaneimidate), [(ON)(NC)C-C(NH)(OCH3)]1- (3), and 2-cyano-2-imidoxy ethaneimidate, [(ON)(NC)C-C(NH)(O)]2- (4), respectively, formed by nucleophilic addition of methanol and hydroxide ion to the coordinatively activated β-carbon of the nitroso-dicyanomethanide. Formation of the hydroxide ion from water in the reaction mixture can be explained by protonation of the C(CN)3- anion. The coordination polyhedra in 1 and 2 are quite different. The coordination polyhedron around the Cu(II) ion in 1 is a distorted trigonal bipyramid and in 2 a distorted square. The Cu(II) ion in 1 is coordinated by four N atoms from two bidentate ligands and one N atom from the NCO- group. The crystal structure consists of discrete molecules with {CuN5} chromophore. On the other hand, the Cu(II) ion in 2 is coordinated by four N atoms from two bidentate ligands in square coordination and the molecules are linked by weaker contacts between copper and oxygen atoms (Cu-O1i = 2.503(3), Cu-O2ii = 2.801(3) Å; i = -x, -y, -z + 1; ii = -x + 1, -y, -z + 1) to infinite chains parallel with c. Thus the coordination polyhedron is completed to an elongated tetragonal bipyramid with the {CuN4O*O*} chromophore. The angle O1i-Cu-O2ii is 167.9(1)° and the crystal structure cannot be considered as molecular but consisting of chains running in one direction. Inspection of the bond distances in mcoe and coe indicates strongly delocalized π-bonding systems. This is also supported by the fact that the anions are almost planar with bond angles close to 120°. The calculated Wiberg (bond-order) indices show that due to conjugation, the bonds within the metallocycle in mcoe and coe exhibit partially multiple character.

Diastereoselective synthesis of 2,6-Imino-D-allonates from chromium carbene iminosugars

Abstract Nucleophilic addition of methanol to ketene equivalents generated by photolysis of pentacarbonyl[1,5-imino-D-ribopyranosylidene]chromium complexes leads diastereospecifically to D-allonates.

Nucleophilic addition of methanol to nitrosodicyanomethanide in the coordination sphere of M II ions (M = Ni, Cu, Co and Pd); nitrosodicyanomethanide as an O-coordinating ligand for nickel(II)

The systems MII-ONC(CN)2 −-L-MeOH-H2O [M = Ni, Cu, Co or Pd; L = pyrazole (pz)] were studied to determine conditions for the nucleophilic addition of MeOH to nitrosodicyanomethanide (ndcm)− in the metal coordination sphere. Compounds containing two or three bidentate anionic chelate ligands derived from methyl-2-cyano-2-(hydroxyimino)ethanimidic acid, H(mcoe), formed by nucleophilic addition of MeOH to ONC(CN)2 −, were isolated: [Cu(mcoe)2(H2O)2] (elongated pseudo-octahedron with two water molecules at long axial distances), [Co(mcoe)3] (approximate octahedron) and [Pd(mcoe)2] (square-planar). In the CoII system, oxidation to CoIII took place. In addition, simple nitrosodicyanomethanide compounds [Ni(ndcm)2(pz)4] (nearly octahedral) and [Pd(ndcm)2(pz)2] (square-planar) were obtained. The crystal structure of trans-[Ni(ndcm)2(pz)4] has been elucidated by X-ray crystallography. The NiII atom is nearly octahedrally coordinated by four nitrogens of pz and two oxygens of (ndcm)−. This compound is the first example of a transition metal oxygen-coordinated nitrosodicyanomethanide complex with a short metal-oxygen bond. The remaining compounds were characterized by i.r. and electronic spectra.

Conformation of coenzyme pyrroloquinoline quinone and role of Ca2+ in the catalytic mechanism of quinoprotein methanol dehydrogenase.

The ab initio structures of 2,7,9-tricarboxypyrroloquinoline quinone (PQQ), semiquinone (PQQH), and dihydroquinone (PQQH2) have been determined and compared with ab initio structures of the (PQQ)Ca2+, (PQQH)Ca2+, and (PQQH2)Ca2+ complexes as well as the x-ray structure of (PQQ)Ca2+ bound at the active site of the methanol dehydrogenase (MDH) of methyltropic bacteria. Plausible mechanisms for the MDH oxidation of methanol involving the (PQQ)Ca2+ complex are explored via ab initio computations and discussed. Considering the reaction of methanol with PQQ in the absence of Ca2+, nucleophilic addition of methanol to the PQQ C-5 carbonyl followed by a retro-ene elimination is deemed unlikely due to large energy barrier. A much more favorable disposition of the methanol C-5 adduct to provide formaldehyde involves proton ionization of the intermediate followed by elimination of methoxide concerted with hydride transfer to the oxygen of the C-4 carbonyl. Much the same transition state is reached if one searches for the transition state beginning with Asp-303-CO2-general-base removal of the methanol proton of the (PQQ)Ca2+O(H)CH3 complex concerted with hydride transfer to the oxygen at C-4. For such a mechanism the role of the Ca2+ moiety would be to (i) contribute to the formation of the ES complex (ii) provide a modest decrease in the pKa of methanol substrate,; and (iii) polarize the oxygen at C-5.