Mechanism of ketone and alcohol formations from alkenes and alkynes on the head-to-head 2-pyridonato-bridged cis-diammineplatinum(III) dinuclear complex

Reactions of the head-to-head 2-pyridonato-bridged cis-diammineplatinum(III) dinuclear complex having nonequivalent two platinum atoms, Pt(N(2)O(2)) and Pt(N(4)), with p-styrenesulfonate, 2-methyl-2-propene-1-sulfonate, 4-penten-1-ol, and 4-pentyn-1-ol were studied kinetically. Under the pseudo first-order reaction conditions that the concentration of the Pt(III) dinuclear complex is much smaller than that of olefin, a consecutive basically four-step reaction was observed: the olefin pi-coordinates preferentially to the Pt(N(2)O(2)) in the first step (step 1), followed by the second pi-coordination of another olefin molecule to the Pt(N(4)) (step 2). In the next step (step 3), the nucleophilic attack of water to the coordinated olefin triggers the pi-sigma bond conversion on the Pt(N(2)O(2)), and the second pi-bonding olefin molecule on the Pt(N(4)) is released. Finally, reductive elimination occurs to the alkyl group on the Pt(N(2)O(2)) to produce the alkyl compound (step 4). The first water substitution with olefin (step 1) occurs to the diaqua and aquahydroxo forms of the complex, whereas the second substitution (step 2) proceeds either on the coordinated OH(-) on the Pt(N(4)) (path a) or on the coordinatively unsaturated five-coordinate intermediate of the Pt(N(4)) (path b), in addition to the common substitution of H(2)O (path c). The reactions of p-styrenesulfonate and 2-methyl-2-propene-1-sulfonate proceed through paths b and c, whereas the reactions of 4-penten-1-ol and 4-pentyn-1-ol proceed through paths a and c. This difference reflects the difference of the trans effect and/or trans influence of the pi-coordinated olefins on the Pt(N(2)O(2)). The pentacoordinate state in path b is employed only by the sulfo-olefins, because these exert stronger trans effect. The steps 3 and 4 reflect the effect of the axial alkyl ligand (R) on the charge localization (R-Pt(IV)(N(2)O(2))-Pt(II)(N(4))) and delocalization (R-Pt(III)(N(2)O(2))-Pt(III)(N(4))-OH(2)); when R is p-styrenesulfonate having an electron withdrawing group, the charge localization in the dimer is less pronounced and the water molecule on the Pt(N(4)) atom is retained (R-Pt(III)(N(2)O(2))-Pt(III)(N(4))-OH(2)) in the intermediate state. In both routes, the alkyl group undergoes nucleophilic attack of water, and the oxidized products are released via reductive elimination.     

Borylene transfer from an iron bis(borylene) complex: synthesis of 1,4-diboracyclohexadiene and 1,4-dibora-1,3-butadiene complexes

Diene to be made: By tuning the size of acetylenic substituents, 1,4-diboracyclohexadiene and unprecedented 1,4-dibora-1,3-butadiene complexes were generated in a controlled manner by borylene transfer from an iron bis(borylene) complex to alkynes (see scheme).     

Peroxy and alkoxy radicals from 2-methyl-3-buten-2-ol

Quantum mechanical calculations were used to determine the structure and energetics of peroxy radicals (P1 and P2) and alkoxy radicals (A1-A3) formed in the atmospheric degradation of 2-methyl-3-buten-2-ol. At the level of theory employed (B3LYP/6-31G(d,p)) low energy conformers were identified with zero, one, or two hydrogen bonds. The beta C-C scission (decomposition) reactions are computed to occur with low barriers, and the 1,5 H-shift (isomerization) reaction of A2 is computed to be of negligible importance. Scission 2 of A2 is computed to be about 93% of the fate of A2, with the balance being scission 1. The new BB1K functional of Truhlar was employed to investigate activation barriers for single intramolecular H-atom transfers across the OH...O* hydrogen bonds, but the barriers to these reactions appear to be too high for these reactions to be important. Extensive searches for transition states for simultaneous double intramolecular H-atom transfer across OH...OH...O* hydrogen bond pairs were unsuccessful.     

2,3-Di(phenylsulfinyl)-1,3-butadiene via a double [2,3]-sigmatropic rearrangement of the bis-sulfenate ester of 2-butyne-1,4-diol.

a one-step conversion of butyne-1,4-diol (1) to 2,3-di(phenylsulfinyl)-1,3-butadiene (4) and the conversion of this bis-sulfoxide to the sulfoxide-sulfone 6 and the bis-sulfone 5 are reported.     

Kinetics and mechanism of the ruthernium(III) catalyzed oxidation of propane-1,3-diol by alkaline hexacyanoferrate(III)

The kinetics of oxidation of propane-1,3-diol by alkaline hexacyanoferrate (III) catalyzed by ruthenium trichloride has been studied spectrophotometrically. A reaction mechanism involving the formation of an intermediate complex between the substrate and the catalyst is proposed. In the rate-determining step this complex is attacked by hexacyanoferate(III) forming a free radical which is further oxidized.     

Formation of filamentous carbon from 1,3-butadiene over a Ni-Pd/Al2O3 catalyst

The formation of carbon filaments from 1,3-butadiene over a Ni-Pd/Al₂O₃ catalyst at 400–450?C was studied by high-resolution electron microscopy and X-ray diffraction analysis. The carbon filaments differ in morphology and in the arrangement of active metal inclusions: (1) abundant ～ 1000 å thick filaments contain biconical alloy particles in the middle of the filament, (2) thin filaments of a thickness less than 500 å rolled in helical fashion contain oval-shaped alloy particles in the middle, and (3) in a few filaments that are less than 200 å thick, alloy particles are positioned at the ends. When the first two types of filaments grow, decomposition of the hydrocarbon occurs at the active sites of the surface with the formation of a carbide microphase with a hexagonal structure. This phase is called the active microphase. When the reaction stops, the active phase decomposes to form carbon and hexagonal nickel. Extensive defects like grain boundaries and stacking fault dislocations are present in the bulk of Ni-Pd alloy particles. The origin of these defects is related to the epitaxial effect of the active microphase particles on the alloy.     

Comparison of free and metal coordinated 1,4-disubstituted-1,4-diaza-1,3-butadienes : Crystal and molecular structures of 1,4-dicyclohexyl-1,4-diaza-1,3-butadiene and trans-[dichloro(triphenylphosphine)(1,4-di-tert-butyl- 1,4-diaza-1,3-butadiene)palladium(II)]

The crystal and molecular structures of c-Hex-DAB (c-hexyl-NC(H)C(H)N-c-hexyl; DAB = 1,4-diaza-1,3-butadiene) and of trans-[PdCl₂(PPh₃)(t-Bu-DAB)] are reported. Crystals of c-Hex-DAB are monoclinic with space group C_2/c and cell constants: a = 24.70(1), b = 4.660(2), c = 12.268(3)Å, β = 107.66(4)°, Z = 4. The molecule has a flat E-s-trans-E structure with bond lengths of 1.258(3)Å for the CN double bond and 1.457(3)Å for the central CC′ bond. These bond lengths and the NC-C′ angle of 120.8(2)° indicate that the C- and N-atoms are purely sp²-hybridized and that there is little or no conjugation within the central DAB skeleton. Crystals of trans-[PdCl₂(PPh₃)(t-Bu-DAB)] are triclinic with space group P-1 and cell constants: a = 17.122(3), b = 18.279(3), c = 10.008(5)Å, α = 96.77(2), β = 95.29(3), γ = 109.79(2). Z = 4. The t-Bu-DAB ligand is coordinated to the metal via one lone pair only. In this 2e; σ-N coordination mode the E-s-trans-E conformation of the free DAB-ligand is still present and the bonding distances within the DAB-ligand are hardly affected. [CN: 1.261(10)Å; CC′: 1.479(10)Å (mean).] The PdN-, NC- and central CC′-bond lengths are compared with those found in other metal -R-DAB complexes.     

Hydroborierung von 3-methyl-1,3-butadien mit 1,2:1,2-bis(tetramethylen)diboran(6)

The nature of the hydroboration product obtained from 3-methyl-1,3-butadiene and 1,2 : 1,2-bis(tetramethylene)diborane(6) (1) allows for the discussion of the reaction mechanism. The hydroboration proceedsby retention of the cyclic structure in the first step, followed by exchange of BH and BC bonds and final cyclic hydroboration to give 1-(boracyclopentyl)-4-(3-methylboracyclopentyl)butane (5). The structural assignment of 5 is based on ¹H, ¹¹B and ¹³C NMR data.     

Studies on the interaction of Eu(III) with lawsone (2-hydroxy-1,4-naphthoquinone), lapachol (2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone), juglone (5-hydroxy-1,4-naphthoquinone) and plumbagin (2-methyl-5-hydroxy-1,4-naphthoquinone)

pH-metric studies show that one mole of Eu(III) interacts with three molecules of each of juglone, plumbagin, lawsone and lapachol in solution. The stability and thermodynamics of these systems (50% aqueous acetone, 0.1 M KNO₃ ionic strength) are discussed and explained.     

1,2- and 1,4-Diacetoxylation of 1,3-butadiene via 2,5-dihydrothiophene 1,1-dioxide as a probable intermediate

Sulphur dioxide has been found to promote a novel liquid-phase oxidation of 1,3-butadiene in acetic anhydride with oxygen gas and catalytic amounts of concentrated protic acids (e.g. hydrobromic acid). 1,2-Diacetoxy-3-butene and 1,4-diacetoxy-2-butene together with small amounts of 1-hydroxy-2-acetoxy-3-butene and 1-hydroxy-4-acetoxy-2-butene are formed in the reaction.     

Isotactic cis-1,4-poly(3-methyl-1,3-pentadiene): a new conformation for isotactic cis-1,4-polydienes

Oriented specimens of isotactic cis-1,4-poly(3-methyl-1,3-pentadiene) exhibit two crystalline modifications characterized, respectively, by the expected two-fold helical conformation with a fiber repeat of 8,02 Å and by a three-fold helix with c = 9,97 Å. The latter highly contracted structure is prevalent in fibers and is the only one observed in unoriented bulk specimens. Consistent with these findings conformational calculations indicate that the three-fold helix is substantially more stable than the two-fold one.     

Synthesis of pyrrolidine and other heterocycles from bu tane-1,4-diol and ethane-1,2-diol

The amination reactions of butane-1,4-diol and ethane-1,2-diol on seven different catalysts obtained by modifying a natural alumosilicate — gumbrin — and a natural zeolite — analcite -with iron and chromium salts, and also by activation with sulfuric acid, have been investigated. The maximum yield of pyrrolidine was obtained in the presence of a catalyst containing ferric oxide on gumbrin.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 937–941, July, 1973.     

2,3-Bis(diphenylphosphynyl)-1,3-butadiene via a double [2,3]-sigmatropic rearrangement. A reinvestigation of the reaction of 2-butyne-1,4-diol with chlorodiphenylphosphine

Contrary to previous reports, the reaction of 2-butyne-1,4-diol with chlorodiphenylphosphine yields 2,3-bis(diphenylphosphinyl)-1,3-butadiene 3 instead of the 1,4-isomer. The structure of the product has been elucidated from ¹H, ¹³C and ³¹P-NMR spectroscopic data.     

Chemistry of Dioxacyclanes: VII. Synthesis of 1,3-Dioxolane Derivatives from 3-(2-Propenyloxy)propane-1,2-diol and Their Properties

2,4-Disubstituted 1,3-dioxolanes were synthesized by reactions of benzaldehyde, its para-chloro derivatives, as well as 3-cyclohexenecarboxaldehyde with 3-(2-propenyloxy)-1,2-propanediol. Theproducts were brought into bromination, dichlorocarbene addition, and epoxidation reactions. It is found that when both components of the heterogeneous reaction of dioxolane ring formation have a double bond, the acid catalyst in strongly deactivated.     

Polymerization and copolymerization of 2-phthalimidomethyll 1,3-butadiene. II. Kinetic study of the polymerization of 1,3-butadiene and of the copolymerization of 1,3-butadiene with 2-phthalimidomethyl 1,3-butadiene initiated by bis-(η3-allyl nickel trifluoroacetate)

The kinetics of the polymerization of 1,3-butadiene initiated by bis(η³-allyl nickel trifluoroacetate) prepared in benzene was studied in methylene chloride at 40°C. The reaction is first order with respect to the monomer, second order with respect to the catalyst in contrast to the case in which solvent is benzene. We have shown that the presence of a polar molecule (fe, N-methyl phthalimide) decreases the overall rate of polymerization. The apparent reactivity ratios for the system 2-phthalimidomethyl 1,3-butadiene (1)-1,3-butadiene (2) are r₁ = 0.65 ± 0.006 and r₂ = 0.48 ± 0.015.