Vinyl Hydrogen Research Articles

Pyridinethiones. VIII. The aldol and wittig condensations of 3‐formyl‐2(1H)‐pyridones, ‐thiones and ‐selones. Preparation of new cyanopyridones

AbstractCondensations of 1‐substituted‐3‐formyl‐2(1H)‐pyridones, ‐thiones and ‐selones with methyl ketones such as acetophenone give the corresponding chalcones in high yields. Geometry at the vinyl hydrogens is E. These chalcones can be cyclized with ethyl cyanoacetate in the presence of ammonium acetate to form new 3‐cyano‐2(1H)‐pyridones. An effective “one‐pot” preparation is worked out and an intermediate from the cyclization reaction is isolated. Via the Wittig reaction it is possible to prepare condensation products from 1‐substituted‐3‐formyl‐2(1H)‐pyridinethiones and ‐selones with mainly Z geometry at the vinyl hydrogens.

Vinyl hydrogen activation in mono- and dinuclear (.eta.5-cyclopentadienyl)(hexatriene)cobalt complexes. Thermal and photochemical hydrogen shifts of complementary stereochemistry

An unprecedented series of thermal vinyl hydrogen shifts in a complexed hydrocarbon ligand, including a thermally reversible photochemical migration to a dinuclear carbene center exhibiting complementary stereochemistry, is reported upon. The work demonstrates novel pathways for ligand rearrangements on dinuclear metal systems, which may also be regarded as homogeneous models for hydrocarbon rearrangement and C-H exchange processes on surfaces.

Acute effects of alkylating agents on canine renal function: specifically designed synthetic maleimides.

Maleimidohippurates and maleimidobenzoates were synthesized that possess a carboxy group for active uptake into renal proximal tubular cells and a reactive maleimide moiety to covalently bond with proximal tubular components. The reactivity of the maleimide moiety in each series was progressively reduced by substitution of methyl groups in place of the vinyl hydrogens. In contrast to N-ethylmaleimide (NEM), the resulting maleimidohippurates and maleimidobenzoates did not possess significant diuretic activity in the dog following renal arterial administration. However, as predicted, the nephrotoxicity of the maleimidohippurates paralleled their in vitro alkylating ability and was quite specifically located in the proximal portion of the canine renal tubule.

ChemInform Abstract: THE REPLACEMENT OF VINYLIC HYDROGEN BY FLUORINE

Chemischer InformationsdienstVolume 13, Issue 36 Preparative Organic Chemistry ChemInform Abstract: THE REPLACEMENT OF VINYLIC HYDROGEN BY FLUORINE J. BURDON, J. BURDONSearch for more papers by this authorI. W. PARSONS, I. W. PARSONSSearch for more papers by this authorA. SHOMMAKHI, A. SHOMMAKHISearch for more papers by this author J. BURDON, J. BURDONSearch for more papers by this authorI. W. PARSONS, I. W. PARSONSSearch for more papers by this authorA. SHOMMAKHI, A. SHOMMAKHISearch for more papers by this author First published: September 7, 1982 https://doi.org/10.1002/chin.198236116Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume13, Issue36September 7, 1982 RelatedInformation

Exchange and isomerization of but-1-ene on supported Pd, Ni, and Pd-Ni alloys

The catalytic reactions between but-1-ene and deuterium on five Pd-Ni alloy catalysts supported on silica were investigated at 23 and −85 °C and compared to supported palladium and nickel catalysts. The hyperfine distribution of monodeuterated but-1-ene was shown to be a specific property of the metals: on palladium the primary vinylic hydrogen atoms are mainly exchanged with deuterium while on nickel the secondary vinylic hydrogen is involved in a proportion of more than 80%. In the alloys, down to 10 atom% palladium concentration, the catalytic properties of palladium are observed; the catalytic behavior of nickel is observed only with a 4 atom% palladium alloy. A surface study with AES and XPS, respectively, on a bulk and supported 4 atom% palladium alloy showed that the palladium surface concentration was near 50%, which is consistent with the catalytic results.

The replacement of vinylic hydrogen by fluorine

In 3 H , 4 H -tetrafluoro-3-thiolen and 1 H ,2 H -octafluorocyclohexene, the conversion of -CHCH- into -CHCF- by fluorination over KCoF 4 takes place by saturation to -CHFCHF- followed by dehydrofluorination, and not by direct replacement of a vinylic hydrogen.

Gas phase hydrogen-deuterium exchange reactions in carbanions: exchange of vinyl and aryl protons by water-d2

This paper reports that under the proper conditions D/sub 2/O can serve as an exchange reagent for hydrogens which are much less acidic than water; as a result, in certain carbanions aryl and vinyl hydrogens can be observed to exchange with D/sub 2/O.

A field ionization kinetics and metastable ion study of the fragmentation of some pentenols

The mechanisms of methyl loss from the molecular ions of three isomeric pentenols, 2-methyl-3-buten-2-ol (I), 3-penten-2-ol (II), and 3-methyl-3-buten-2-ol (III),.and the structures of the resulting fragment ions have been investigated using isotopic labelling, metastable ion studies, and field ionization kinetics (FIK) studies. The molecular ion of I loses predominantly the methyl group in the α position with respect to the hydroxyl group and allylic to the double bond, to form the protonated methyl vinyl ketone ion, although a minor loss of a methyl group incorporating the three vinylic hydrogen atoms is observed for long-lived molecular ions. FIK studies of the fragmentations of CH 3CH CHCH(OH)CD 3 +. (IIa) and CH 2 C(CH 3)CH(OH)CD 3 +. (IIIa) show, for both isomers, loss of both CD 3 and CH 3 at reaction times < 10 −10.5 s, with loss of CH 3 predominating at times between 10 −10 and 10 −9 s; loss of CD 3 increases in importance again for long-lived ions fragmenting as metastable ions in the drift regions. The initial loss of CD 3 at short times is shown to be the result of simple cleavage yielding the appropriate protonated aldehyde. Rapid [ 1,2 ] H-shifts yield the enol ion of the appropriate propyl methyl ketone which fragments by loss Of CH 3 to give protonated vinyl methyl ketone. At longer times a further [1,4] shift of the hydroxylic hydrogen atom yields the propyl methyl ketone molecular ion which fragments by loss of CD 3. Evidence for this complex series of hydrogen shifts is presented in terms of metastable ion intensities and kinetic energy releases in metastable ion fragmentation reactions.

Interpretation of the resonance Raman spectrum of bathorhodopsin based on visual pigment analogues.

Resonance Raman spectra of visual pigment analogues have been used to evaluate various models for the structure of the retinal chromophore in bathorhodopsin. Deuteration or removal of the 18-methyl on the beta-ionyl ring or of the 19-methyl on the polyene chain demonstrates that the three intense low wavenumber bands of bathorhodopsin at 853, 875, and 920 cm-1 are not due to exomethylene or ring modes. Rather, assignment of these lines to out-of-plane vinyl hydrogen motions on the chain best accounts for the experimental data. Our calculations show that the intensity of these vibrations can be explained by twists of 10-30 degrees about chain single bonds. The 1100-1400-cm-1 Raman fingerprint indicates that the configuration of the double bonds is trans. This suggests that the structure of the bathorhodopsin chromophore is twisted all-trans.

Triarylphosphine-Palladium Complexes

Aryl, heterocyclic, benzyl, and vinylic halides undergo facile reactions with carbon monoxide or olefins forming new carbon-carbon bonds under the influence of triarylphosphine-palladium catalysts. The carbon monoxide reactions produce esters in the presence of alcohols, amides in the presence of amines, and aldehydes in the presence of hydrogen. Reactions with olefins produce new olefins in which a vinylic hydrogen is replaced by the organic group from the halide. Some olefins and vinylic halides require the presence of secondary amines to react, in which instance tertiary allylic amines are formed catalytically. Conjugated dienes may be used in place of simple olefins to form products with additional unsaturation. Numerous applications for these reactions in organic synthesis appear likely.

ChemInform Abstract: PALLADIUM‐PROMOTED VINYLIC HYDROGEN SUBSTITUTION OF ALKENE AND α CARBONYLATED ALKENE BY LITHIUM AND MAGNESIUM ORGANOCUPRATES

Chemischer InformationsdienstVolume 11, Issue 11 Isocyclic Compounds ChemInform Abstract: PALLADIUM-PROMOTED VINYLIC HYDROGEN SUBSTITUTION OF ALKENE AND α CARBONYLATED ALKENE BY LITHIUM AND MAGNESIUM ORGANOCUPRATES N. T. LUONG-THI, N. T. LUONG-THISearch for more papers by this authorH. RIVIERE, H. RIVIERESearch for more papers by this author N. T. LUONG-THI, N. T. LUONG-THISearch for more papers by this authorH. RIVIERE, H. RIVIERESearch for more papers by this author First published: March 18, 1980 https://doi.org/10.1002/chin.198011188AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume11, Issue11March 18, 1980 RelatedInformation

Grafting starch xanthate with vinyl monomers and hydrogen peroxide in foam rubber production

AbstractStarch xanthate with degrees of substitution (D.S.) ranging from 0.12 to 0.56 reacted with vinyl monomers (acrolein, acrylamide, acrylic acid, acrylonitrile, methyl acrylate, or styrene) and hydrogen peroxide to form aqueous gels of starch–polyvinyl monomer graft copolymer. The same reactions conducted in a rubber latex medium resulted in a self‐acidifying, self‐heating, and self‐foaming coagulation to give a foam rubber. Such products were formed from several synthetic latices (NBR, SBR, polyisoprene, and polychloroprene types) and natural rubber latex; noted for each were the effects of the D.S., of monomer and peroxide concentrations, and of starch:elastomer ratios. The dried foams were evaluated by standard strength tests. Foam rubber of acceptable extensibility and enhanced tensile strength (up to 110 psi) was obtained with 0.12–0.15 D.S. xanthate and with proper balance of vinyl monomer, peroxide, and starch:elastomer ratio. Resilience was fair to good, but compression set was rather poor compared to most foam rubbers of general use.

The mechanisms of dimethylbutene isomerization over alumina

Reactions of dimethylbutenes over pure and chlorided γ-alumina have been studied in the presence of selective poisons and/or with various host molecules for deuterium label. The extent of H 2S poisoning has been used to determine the relative roles of π-allylic species and alkyi carbonium ions in the isomerization of the 2,3-dimethylbutenes on alumina at 273 K. The absence of poisoning by H 2S of skeletal isomerization of 3,3-dimethylbut-l-ene at 352 K is evidence that H2S does not inhibit reaction through carbonium ions whereas it is known to poison activity involving π-allylic species. The isomerization of 3,3-dimethylbut-l-ene in the presence of suitably labeled alkenes showed that vinylic and allylic hydrogen atoms can equilibrate with Brønsted-acid-type hydrogen on alumina at about 273 K. But adsorbed vinyl species have been found to retard skeletal isomerization, suggesting identity, or at least close proximity, of the sites for Brønsted acid reactions and vinylic CH exchange. Catalyst chloriding enhanced isomerization but retarded exchange of CH bonds with D. The influence of activation temperature and of impurities is discussed for reactions of dimethylbutenes over alumina.

Crosslinking of Starch Xanthate. V. Redox Grafting with Hydrogen Peroxide and Vinyl Monomers in Water

Soluble starch xanthate (SX) with a degree of substitution (D. S.) ranging from 0.09 to 0.56 reacted with vinyl monomers (acrolein, acrylamide, acrylic acid, acrylonitrile, methyl acrylate, or styrene) and hydrogen peroxide to form aqueous gels of crosslinked starch—poly(vinyl monomer) graft copolymer. The reaction progress was followed by viscometry while investigating the effects of varied D. S. and monomer and peroxide levels. Solids, precipitated from the gels by ethanol, were analyzed for nitrogen and sulfur and their compositions were calculated. The vinyl monomer polymerization ranged from 30 to 98% in the grafting. A residual sulfur content was equivalent to a remainder xanthate D. S. of 0.04 to 0.24. Infrared absorption spectra verified copolymer formations and indicated that homo-polymer formation was minimal.

Pd-promoted vinylic hydrogen substitution of alkene and α carbonylated alkene by lithium and magnesium organocuprates.

In the presence of PdCl 2, LiCl and K 2CO 3, vinylic hydrogen substitution of styrene and acrylic ester, in MeCN and MeCN - HMPA respectively, has been successfully performed using lithium and magnesium organocuprates.

A coordinatively unsaturated, polymer-bound palladium(0) complex. Synthesis and catalytic activities

A coordinatively unsaturated palladium(0) complex was prepared by the reduction of a polymer-bound palladium(II) chloride complex, which was prepared by the reaction of poly-4-diphenylphosphinomethylstyrene with palladium chloride, with hydrazine in ethanol in the presence of triphenylphosphine. Catalytic activities of the polymerbound palladium(0) complex were examined for three representative types of palladium(0)-induced reactions involving oxidative addition of halides to the metal: (i) vinylic hydrogen substitutions with aryl halides, (ii) acetylenic hydrogen substitutions with aryl halides, (iii) vinylic halogen substitutions with Grignard reagents. Use of the catalyst resulted in formation of corresponding products in good yields. The catalytic activity is comparable to that of analogous homogeneous catalysts, yet is not remarkably lowered on being recycled.

Palladium-promoted vinylic hydrogen substitution of alkenes by Grignard reagents. Stoicheiometric and catalytic reactions

Arylation of styrene by Grignard reagents has been performed in the presence of stoicheiometric or catalytic amount of palladium chloride.

Nucleophilic Substitution of Vinylic Hydrogen Atoms by Carbanions

Chain elongation of activated terminal olefins can be accomplished by the reaction sequence (1)→(2)→(3). It is also feasible with R = tert‐butyl, cyclopropyl, and other bulky groups. equation image

The nature of active sites on aluminum phosphate for the isomerization of butenes

The nature of active sites on aluminum phosphate for the isomerization of n-butenes was investigated by means of a tracer study which consisted of isomerization over deuterated catalyst and co-isomerization of light and perdeuterated butene. There exist three kinds of active sites, Brönsted acid sites, Lewis acid sites where intermolecular hydrogen transfer occurs (L-inter sites), and Lewis acid sites where intramolecular hydrogen transfer occurs (L-intra sites). Their contributions to n-butene isomerization, which were quite dependent on the thermal treatment of the catalyst, were calculated for different evacuation temperatures. At low evacuation temperature, Brönsted acid sites and L-inter sites are the main active sites, while L-intra sites become prominent at high evacuation temperature. L-intra sites are characteristically active for cis-trans rotation. The adsorption state of butene molecules was also examined. From the isotopic distributions of butene isomers, it was concluded that secondary butyl carbenium ion intermediates on Brönsted acid sites and L-inter sites were adsorbed weakly, and all bonds of the intermediates rotated freely. Over L-intra sites, the isomerization may be initiated by the abstraction of H − at the vinyl hydrogen of butene.

Reactions of 3,3-dimethylbut-1-ene with deuterium or deuterium oxide on oxide catalysts

The reactions of 3,3-dimethylbut-1-ene (I) over a copper X zeolite, magnesium oxide and γ-alumina have been studied in the presence of either deuterium or deuterium oxide. Products obtained by exchange and/or isomerization have been analysed using a combined gas chromatograph-mass spectrometer. Over CuX with D2O, I underwent isomerization at 417 K to give 2,3-dimethylbut-1-ene (II) and 2,3-dimethylbut-2-ene (III), but did not itself exhibit direct exchange. Both II and III formed initially showed similar but extensive incorporation of deuterium. On magnesium oxide with D2 at 493 K, I exchanged, the vinyl hydrogens being replaced faster than those in the methyl groups. No isomerization was detected. Over γ-alumina at 328 K and with D2 present, I rapidly isomerized to give a mixture of II and III, but little deuterium incorporation accompanied this reaction and only a very limited exchange of I occurred.