Olefinic Linkage Research Articles

Mechanism of Linkage Isomerization in (η1-5-Chloropentene)pentacarbonylchromium(0)

(η1-5-Chloropentene)pentacarbonylchromium(0), (η1-ol−Cl)Cr(CO)5, 1, and (η2-5-chloropentene)pentacarbonylchromium(0), (η2−Cl−ol)Cr(CO)5, 2, respectively, in which 5-chlorobenzene is bonded to Cr via a lone pair on chlorine or through the olefinic linkage, respectively, are produced via pulsed laser flash photolysis of Cr(CO)6/Cl−ol solutions. Compound 1 then isomerizes to 2 on the submillisecond time scale. This process has been monitored both by IR and visible spectrophotometry by employing fluorobenzene (FB) as an inert diluent. Parallel studies of flash photolysis of Cr(CO)6 in solutions containing 1-chlorobutane and 1-hexene, both neat and diluted with FB, where the Cl and ol functional groups are not linked, also were carried out. The data support a dissociative isomerization mechanism involving rate-determining Cr−Cl bond breaking. Activation parameters for this process have been obtained. The accessibility of a proposed low-energy pathway involving “agostic” C−H−Cr interactions in the transition st...

17O NMR Spectra of Divinyl Ethers

The 17O NMR spectra of a number of alkyl- and phenyl-substituted divinyl ethers were recorded in CDCl3 solution. The relationship between chemical shift and the number, nature and position of substituents was explored. The shift values, falling in the range δ 100–140 ppm, were found to be remarkably insensitive to the electronic and stereochemical effects of substituents. The narrow range of chemical shifts is likely to arise from the ability of the O atoms of divinyl ethers to share p–π conjugation with the two olefinic linkages: reduced conjugation with one vinyl group may lead to enhanced conjugation with the other. © 1997 by John Wiley & Sons, Ltd.

Synthetic Study of Piericidins. I. Synthesis of the Side Chain of Piericidin B1.

The side chain of piericidin B1 having four (E)-olefinic linkages was prepared. The coupling reaction of the non-conjugated aldehyde (22) derived from 4, 4-dimethoxy-2-butanone and the sulfone (13) afforded a diastereomeric mixture of the hydroxy sulfone (27). Benzoylation of 27 followed by reductive olefin formation with sodium amalgam gave the desired all-trans-tetraene (29) possessing an (E)-C(5)-C(6) double bond, which was transformed to the alcohol (1) corresponding to the side chain of piericidin B1.

Structure-activity modifications of the HIV-1 inhibitors (+)-calanolide A and (-)-calanolide B.

The delta 7,8 olefinic linkages within (+)-calanolide A(1) and (-)-calanolide B(2) were catalytically reduced to determine impact on the anti-HIV activity of the parent compounds. In addition, a series of structure modifications of the C-12 hydroxyl group in (-)-calanolide B was made to investigate the importance of that substituent to the HIV-1 inhibitory activity of these coumarins. A total of 14 analogs were isolated or prepared and compared to (+)-calanolide A and (-)-calanolide B in the NCI primary anti-HIV assay. While none of the compounds showed activity superior to the two unmodified leads, some structure-activity requirements were apparent from the relative anti-HIV potencies of the various analogs.

17O NMR study of p‐π conjugation in methoxybutadienes and related compounds

AbstractThe 17O NMR spectra of some monomethoxy and dimethoxy derivatives of buta‐1,3‐diene, hexa‐2,4‐diene, cyclohexa‐1,3‐diene and cyclohexa‐1,4‐diene were recorded in CDCl3. The δ(17O) values show that in 2‐methoxybuta‐1,3‐diene the efficiency of p‐π conjugation in the OCC moeity is significantly lowered by cross‐conjugation of the CC bond with the other olefinic linkage. In the related system of 2‐methoxycyclohexa‐1,3‐diene, however, the corresponding effect is much smaller, apparently because of weak conjugative π‐π interaction in the olefinic system. On the other hand, the strength of p‐π conjugation appears to be the same in the OCCCC moieties of both 1‐methoxybuta‐1,3‐diene and 1‐methoxycyclohexa‐1,3‐diene. Moreover, as a transmitter of substituent effects, the unsaturated system of cyclohexa‐1,3‐diene is comparable to that of the benzene nucleus.

Reactions of [Et3NH][(μ‐CO)(μ‐RS)Fe2(CO)6] with acetylenes. Synthesis of (μ‐σ,π‐p‐MeC6H4CCHPh)(μ‐RS)Fe2(CO)6 and (μ‐σ,π‐PhCCHC6H4Me‐p)(μ‐RS)Fe2(CO)6. The crystal structure of (μ‐σ,π‐p‐MeC6H4CCHPh)(μ‐tBuS)Fe2(CO)6

AbstractThe reactions of [Et3NH][μ‐CO)(μ‐RS)Fe2(CO)6] (1a‐d) (RnPr, nBu, tBu, Ph) with p‐MeC6H4C°CPh or m‐NO2C6H4C°CPh were studied and products of the vinyl type (μ‐σ,π‐p‐MeC5H4CCHPh)(μ‐RS)Fe2(CO)6 (2) and (μ‐σ, π‐phCCHC6H4Me‐p) (μ‐RS)Fe2(CO)6 (3) (RnPr, nBu, tBu, Ph) were obtained. While the structures of all the compounds 2a‐d and 3a‐d were characterized by elemental analysis, IR, 1H NMR and MS spectroscopies, the single‐crystal structure of 2c(RtBu) was determined by X‐ray diffraction method. The X‐ray diffraction result of 2c showed that the substituted vinyl ligand p‐MeG6H4CCHPh bridges the two iron centers, being σ‐bonded to one metal through the olefinic carbon attached to p‐MeC6H44 group, while π‐bonded to the other via olefinic linkage; the Fe2(CO)6 and proton units are in a cis fashion and the tBu group is bonded to sulfur atom through an e‐type of bond.

Relative thermodynamic stabilities of 2‐(methoxymethylene)tetrahydrofuran and 5‐methoxymethyl‐2,3‐dihydrofuran

AbstractThe relative thermodynamic stabilities of the title compounds were determined by iodine catalyzed chemical equilibration in cyclohexane solution. The main point of interest was a determination of the thermodynamic stability of the OCCO moiety found in the exocyclic isomers, i.e. the stabilizing effect of a MeO group on the olefinic linkage of 2‐methylenetetrahydrofuran. All three isomeric compounds have essentially similar enthalpy values, which, in comparison with some previous thermodynamic data, shows that the double bond stabilization energy of the MeO group in the exo isomers is only ca 3 kJ mol−1. The entropy difference between the geometrical isomers is negligible, whereas the endo isomer is favoured by an entropy contribution of ca 9 J K−1 mol−1.

In‐situ poling and synthesis of NLO chromophore‐bearing polyurethanes for second harmonic generation

AbstractThe preparation of six diol and one triol monomers bearing donor–acceptor chromophores is described. The monomers contain the N,N′‐bis(2‐hydroxyethyl)aniline unit with various acceptor groups attached in some cases via azo or olefin linkages, at the para position. Acceptors studied include nitro, tricyanovinyl, cyclobutene‐1,2‐dione, and imidazolidine‐2,4‐dione. Poled polymer films were prepared by thermal polymerization of these with 2,4‐toluenediisocyanate (TDI) in the presence of an electric field generated by a corona tip. The resulting thin (ca. 1 μm), glassy polymer films were shown to exhibit reasonably good second harmonic generation efficiencies. Preliminary results show that the polymers with higher Tg's have the best temporal stability. The polymer derived from the diol bearing an imidazolidine‐2,4‐dione acceptor shows only a ca. 30% decrease in its second harmonic generation (SHG) signal over 200 days at room temperature, even though it is not crosslinked. We attribute this to hydrogen bonding interactions from the urethane and imidazolidine‐2,4‐dione groups. A crosslinked film derived from the triol and TDI has an exceedingly stable SHG response at room temperature, and no decrease in the SHG response is observed at 100°C for a few hours. © 1993 John Wiley & Sons, Inc.

New alkynyl- and vinyl-linked benzo- and aza-crown etherbipyridyl ruthenium(II) complexes which spectrochemically recognize Group IA and IIA metal cations

A new alkynyl-linked bis(benzo-15-crown-5) bipyridyl ligand and new mono- and bis-benzo-15-crown-5 and aza-15-crown-5 bipyridyl ligands containing trans-conjugated olefinic linkages between the crown ethers and the 4,4′-disubstituted 2,2′-bipyridine (bipy) moieties have been synthesised. The corresponding [RuL(bipy)2][PF6]2 and [RuL3][PF6]2 complexes have been prepared and the latter electropolymerized onto optically transparent conducting glass electrodes. Electronic absorption and fluorescence-emission spectroscopic measurements have demonstrated spectrochemical recognition of Group IA and IIA metal cations by the novel functionalized crown ethers both as solution complexes and as polymeric films. The λmax and Iµ values for both the low-energy ligand-based π–π* transition and the metal-to-ligand charge transfer band observed for the complexes are sensitive to the binding of sodium and magnesium cations. The spectral measurements further demonstrate the presence of residual unsaturated linkages in the electropolymerized films, providing a technique that could be applied to probe the mechanisms and efficiencies of such electropolymerizations.

Applications of methylsulfonylsulfene in synthesis. Part 1. Conversion of 3,4-dihydro-2H-pyran into cis-2-(C-substituted)tetrahydropyran-3-sulfonates/sulfinates

(1R*,6S*,8R*)-8-Methylsulfonyl-2-oxa-7-thiabicyclo[4.2.0]octane 7,7-dioxide 10a, available from the reaction of 3,4-dihydro-2H-pyran and methylsulfonylsulfene 1(generated in situ from MeSO2Cl and Et3N), underwent alkylation at position 8 in the presence of sodium hydride and alkyl halides. With methyl iodide and chloromethyl methyl ether, mixtures of the endo- and exo-methyl derivatives 10b and 11b(with 10b in predominance) and the endo- and exo-methoxymethyl derivatives 10c and 11c(with 11c in predominance) were produced. With benzyl chloride, tert-butyl bromoacetate and allyl bromide, only the exo-alkyl derivatives 11d-f were isolated, the stereostructure of compound 11f being established by X-ray crystallography.In the presence of sodium thiophenoxide and thiophenol, compound 10a underwent a reductive cleavage of its S(7)–C(8) bond to give, after acidification, the sulfinic acid 9a; the sodium salt of the last-cited acid underwent methylation with methyl iodide to give (2S*,3S*)-3-methylsulfonyl-2-(methylsulfonylmethyl)tetrahydropyran 15d. Under corresponding conditions (and also in the presence of a large excess of Na/Hg in MeOH), compound 11f afforded the sulfinic acid 27c which was transformed into (2R*,3S*)-3-methylsulfonyl-2-[(1′R*)-1′-(methylsulfonyl)but-3′-enyl]-tetrahydropyran 21d; the stereostructure of the last cited compound was determined by X-ray crystallography. The sulfinic acid 27c also underwent reaction with diazomethane to give the methyl sulfinate 27b as a ∼ 1 : 1 mixture of diastereoisomers.In the presence of Raney nickel, compound 10a furnished (2R*)-2-(methylsulfonylmethyl)-tetrahydrofuran 14 whereas compound 11f underwent reduction of its olefinic linkage to give the propyl derivative 11h.Sodium methoxide in methanol (and also Na/Hg in MeOH) induced an overall hydrolytic cleavage of the S(7)–C(8) bonds of compounds 10a and 11f to give, after acidification, the cis-sulfonic acids 15c and 21b(which were isolated as their methyl esters 15a and 21a). In the presence of sodium hydroxide, the cis-sulfonic acid 15c underwent epimerisation at position 2 to give the trans-sulfonic acid 17c(which was isolated as its methyl ester 17a).

Oxidation of dyes by manganese tetraphenyl porphyrin activated peroxy bleach

The oxidation of a number of dyes in predominantly aqueous systems by tetraphenylporphyrinato manganese(III) imidazole, MnTPP(Im), activated peroxy bleach has been studied in the context of application in detergent systems. Dyes with an olefinic linkage in the chromophoric group are readily oxidized by perborate even in the absence of the activator. On the other hand, dyes with an azo linkage are resistant to oxidation and are bleached only to a limited extent (25%) even by MnTPP(Im) activated perborate. In the presence of a surfactant, alkylbenzene sulphonate, bleaching is further inhibited by micellar solubilization of the dyes. Sulphonation of MnTPP(Im) only marginally improves the bleaching efficiency in presence of the surfactant. MnTPP(Im) is also destroyed by perborate in the absence of the substrate. In view of these limitations, the metalloporphyrin activated peroxy bleach system is not promising for application in detergent systems. Attempts have also been made to explain the difference in the behaviour of different substrates on structural consideration.

Thermoanalytical characteristics of polycarboxylic acids investigated as durable press agents for cotton textiles

AbstractPolycarboxylic acids are of great interest to the cotton textile industry as durable press agents because they do not release substances that require mandatory monitoring. Differential scanning colorimetric (DSC), thermogravimetric (TG), and differential thermogravimetric (DTG) techniques were used to study the thermal characteristics of a series of 10 polycarboxylic acids. Samples included di‐, tri‐, and tetra‐functional compounds some of which contained olefinic linkages, hydroxyl substituents, and cyclic structure. Thermogravimetric data at simulated fabric cure temperatures was used to assess the potential of a compound for use as a textile finishing agent. In high‐temperature studies the compounds were readily distinguishable in DSC analyses. General characteristics such as increases in total heats of reactions were found to be related to the number of functional groups. These results also provided support for a mechanism for the reaction of polycarboxylic acids with cellulose through an anhydride intermediate.

Octahedral metal carbonyls LXXII. Volumes of activation for solvent displacement in (solvent)M(CO)5 transients (M = Cr, Mo, W) generated from M(CO)6 via pulsed laser flash photolysis

Pulsed laser flash photolysis of M(CO)6 (M = Cr, Mo, W) in aliphatic and aromatic hydrocarbon solutions (solvent = n-C7H16 and C6H5X (X = F, Cl, H, CH3)) produces (solvent)M(CO)5 transients, which then react with Lewis bases (L; 1-hexene, piperidine, 2-picoline, pyridine) to afford LM(CO)5 products. The solvent-displacement process has been studied at variable pressures to 150 MPa, and volumes of activation for this process have been determined. These volumes of activation are sensitive to the identity of the coordinated solvent and suggest that bonding of chlorobenzene to Cr takes place via a lone pair of electrons on Cl, but through an isolated olefinic linkage for benzene, fluorobenzene and toluene. Observed volumes of activation also are consistent with the accessibility of an interchange mechanism for solvent displacement of n-heptane and with a dissociative solvent displacement mechanism for the arenes and support an increasing contribution from the solvent interchange process vs. reversible solvent dissociation in the order of the increasing size of the metal atom, Cr<Mo ⋍ W. The observed ability of “[M(CO)5]” to discriminate among various nucleophiles arises in part from the accessibility of these two competitive mechanisms.

Variation of the inhibition of calmodulin dependent cyclic AMP phosphodiesterase amongst analogues of tamoxifen; Correlations with cytotoxicity

The ability of a variety of analogues of tamoxifen to inhibit calmodulin dependent cyclic AMP phosphodiesterase has been determined. Effective inhibition requires that the aminoethoxy side chain bears a positive charge at physiological pH and is not too bulky. Amongst 4-substituents, inhibitory potency increases with lipophilicity. The stereochemistry about the olefinic linkage is not important. The most potent agent found ( ic 50 1.4 μM, compare tamoxifen = 6.75 μM) has a 4-iodine substituent and pyrrolidino in place of dimethylamino. This analogue is also more cytotoxic than tamoxifen against MCF-7 human breast cancer cells as determined in a 24-hr assay, but there was no correlation found between calmodulin inhibition and cytotoxicity against the L1210 murine leukaemia or Walker rat carcinosarcoma cells in culture. The results are consistent with the possibility that calmodulin is important to the functioning of oestrogen receptor mediated growth in MCF-7 cells.

Chemical change involved in the oxidative reductive depolymerization of hyaluronic acid.

The oxidative reductive depolymerization (ORD) of hyaluronate has been investigated. A solution of hyaluronate (Mr 4.07 x 10(5] in phosphate buffer (pH 7.2) was incubated in the presence of Fe2+ for 24 h at 37 degrees C under an oxygen atmosphere to yield depolymerized hyaluronate (ORD fragments; an average Mr of 2,600). The ORD fragments contain 21 and 24% less hexosamine and uronic acid, respectively, but no olefinic linkage. They were exhaustively digested with chondroitinase AC-II. The resulting oligosaccharides and monosaccharides were separated by gel filtration and ion-exchange chromatography, and their structures were determined by proton and carbon-13 NMR, fast atom bombardment mass spectrometry, and chromatographic techniques combined with chemical modifications. The following structures derived from the reducing ends of the ORD fragments were identified: 4,5-unsaturated GlcA(beta 1----3)-N-acetyl-D-glucosaminic acid (where GlcA- represents glucuronosyl-) (21%), 4,5-unsaturated GlcA(beta 1----3)GlcNAc(beta 1----3)-D-arabo-pentauronic acid (24%), and N-acetyl-D-glucosamine (51%). The following structures derived from the nonreducing ends were identified: L-threo-tetro-dialdosyl-(1----3)GlcNAc (a tentative structure, 8%), N-acetylhyalobiuronic acid (20%), and N-acetyl-D-glucosamine (45%). The results indicate that the ORD reaction of hyaluronate proceeds essentially by random destruction of unit monosaccharides due to oxygen-derived free radicals, followed by secondary hydrolytic cleavage of the resulting unstable glycosidic substituents.

Redox-responsive crown ethers containing a conjugated link between the ferrocene moiety and a benzo crown ether

The syntheses of new redox-active crown ethers containing cis- and trans-conjugated olefinic linkages between the ferrocene redox center and respectively benzo-15-crown-5 and N-phenylaza-15-crown-5 are described. The sodium cation forms complexes with trans ferrocenyl ionophores, whereas potassium produces intermolecular sandwich complexes with the same ligands, which were also observed by fast atom bombardment mass spectrometry. Electrochemical investigations reveal the binding of Na + , K + , and Mg 2+ guest cations at the respective crown ether coordinating sites results in shifts of the ferrocene oxidation wave to more positive potentials

Novel mono- and di-ferrocenyl bipyridyl ligands: syntheses, electrochemistry, and electropolymerisation studies of their ruthenium(II) complexes

The syntheses and electrochemical properties of new mono- and di-ferrocenyl bipyridyl ligands containing trans conjugated olefinic linkages between the ferrocene redox centres and the 4,4′-substituted 2,2′-bipyridine (bipy) moieties are described. The corresponding ruthenium(II) complexes have been prepared and one complex, [RuL4(bipy)2][PF6]2[L4= 4,4′-bis(ferrocenylvinyl)-2,2′-bipyridine], undergoes electrochemical polymerisation to produce an electrochromic polymer film.

Concerning the role of 24,25-dihydrolanosterol and lanostanol in sterol biosynthesis by cultured cells

Rat hepatoma cells (H4-II-E-C3) efficiently converted a dietary supplement of [2- 3H]24,25-dihydrolanosterol ( 1 ) to [ 3H]cholesterol while [2- 3H]lanostanol (4,4,14α-trimethyl-cholestanol( 2 ) was recovered from the cells without apparent transformation, although it was esterified and induced an accumulation of lanosterol. A comparison of the Chromatographic (TLC, GLC and HPLC), spectral (MS and 1H-NMR) and physical properties of 1 and 2 is given for the first time. The inability to detect 2 in nature coupled with our findings that 1 but not 2 is metabolized to cholesterol by H4 cells is interpreted to imply that the biosynthetic inclusion of the Δ 8(9)-bond during the cyclization process of squalene-oxide to a tetracyclic product is an evolutionary adaptation selected for because the olefinic linkage is structually important in the subsequent conversion of lanosterol and its stereoisomers, e.g., cycloartenol, to Δ 5-sterols.

Mechanisms of induction of enzymes that protect against chemical carcinogenesis

A persuasive body of evidence indicates that substantial protection against chemical carcinogenesis can be achieved by induction of enzymes concerned with the metabolism of carcinogens. There are two classes of anticarcinogenic enzyme inducers: (a) monofunctional inducers (e.g., phenolic antioxidants, isothiocyanates, coumarins, thiocarbamates, cinnamates, 1,2-dithiol-3-thiones) that elevate Phase II enzymes (such as glutathione S-transferases, NAD(P)H:quinone reductase, UDP-glucuronosyl-transferases) in various tissues without significantly raising the Phase I enzyme, aryl hydrocarbon hydroxylase (cytochrome P1-450); and (b) bifunctional inducers (e.g., polycyclic aromatic hydrocarbons, flavonoids, and azo dyes) that induce both Phase I and Phase II enzymes of xenobiotic metabolism. Induction of Phase II enzymes appears to be a sufficient condition for achieving chemoprotection, and since certain Phase I enzymes are responsible for activating carcinogens to their ultimate reactive forms, selective Phase II enzyme inducers offer intrinsically safer prospects for achieving chemoprotection. Whereas induction of both Phase I and II enzymes by bifunctional inducers depends on the Ah receptor, induction of Phase II enzymes by monofunctional inducers is independent of a functional Ah receptor. Studies on the structural requirements for induction of quinone reductase [NAD(P)H:(quinone acceptor) oxidoreductase; EC 1.6.99.2] by monofunctional inducers in Hepa 1c1c7 murine hepatoma cells have revealed that such inducers contain a distinctive chemical feature (or acquire this feature by metabolism) that regulates the synthesis of this protective enzyme. The inducers are all Michael reaction acceptors characterized by olefinic (or acetylenic) linkages that are rendered electrophilic by conjugation with electron-withdrawing groups. Typical examples are alpha, beta-unsaturated aldehydes, ketones (including quinones), thioketones, sulfones, esters, nitriles and nitro groups. The potency of these inducers parallels their reactivity as Michael acceptors. These generalizations have provided mechanistic insight into the vexing question of how so many seemingly unrelated anticarcinogens induce chemoprotective enzymes. They have also led to the prediction of entirely new and unsuspected structures of inducers, with potential for chemoprotective activity.

Octahedral metal carbonyls: LXV. Olefin isomerization in (2-allylphenyldiphenylphosphine)tetracarbonyltungsten(0)

The stepwise displacement of pip (= piperidine) from cis-(pip) 2W(CO) 4 by 2-allylphenyldiphenylphosphine (adpp) affords cis-(η 3-adpp)W(CO) 4 ( 4) when the cis-(pip)(η 1-adpp)W(CO) 4 intermediate ( 2; adpp is P-bonded) is isolated and purified; directly, this reaction affords a 85/15 ratio of 1 to cis-(η 3-pdpp)W(CO) 4 ( 3; pdpp = 2-propenylphenyldiphenylphosphine). In contrast, it had been reported that displacement of norbornadiene (= NBD) from (η 4-NBD)M(CO) 4 by adpp affords primarily 3. It is concluded that olefin bond-migration takes place in a η 3-allylmetal hydride intermediate produced from a [(η 2-adpp)W(CO) 4] precursor in which adpp is coordinated cis to a vacant coordination site through the olefinic linkage.