Trans Vinyl Research Articles

Merging single-electron transfer and energy transfer processes of photocatalyst: An atom economical strategy for the synthesis of 1-trifluoroethylated isoquinolines from cis and trans vinyl isocyanides

Photoredox-catalyzed radical cascade trifluoroethylation-cyclization of cis and trans vinyl isocyanides with trifluoroethyl iodide involving an unusual single-electron transfer and energy transfer processes of photocatalyst provides an atom economical method for the synthesis of 1-trifluoroethylated isoquinolines. The process is notable for its operational simplicity and good functional group tolerance.

Mesomorphism Dependence on Cis-Trans Configuration and Varying Terminal/Lateral Group

A chalconyl trans vinyl ester homologous series of thermotropic liquid crystals RO-C6H4-CH=CH-COO-C6H4-CH=CH-CO-C6H3 (OCH3)2 meta-para is synthesized and studied with a view to understand and establish the relation between molecular structure and mesomorphism or mesomorphic behaviors. Novel homologous series consists of thirteen homologues (C1 to C18). First five (C1 to C5) homologues are nonmesogenic. Rest of the homologues (C6 to C18) homologues is mesogenic. Monotropically smectogenic character appears from C6 to C10 homologue and C12 to C18 homologues are enantiotropically smectogenic. Nematogenic property is totally absent throughout a series. Textures of smectic phase are of the type smectic A or C. Transition curves of a phase diagram behaved in normal manner. Analytical, spectral and thermal data supports the molecular structures of homologues. Odd-even effect is observed for Sm-I/I-Sm transition curve. Thermal stability for smectic is 93.7 °C and the mesomorphic phase lengths from enantiotropic homologues for smectic from minimum to maximum is 6.0 °C to 28.0 °C at the C12 and C18 homologue respectively. Series is smectogenic without exhibition of nematic property. The group efficiency order on the basis of thermal stability is derived; from comparative study of present series and analogous series.

Mesomorphism Dependence on Cis-Trans Configuration and Varying Terminal/Lateral Group

A chalconyl trans vinyl ester homologous series of thermotropic liquid crystals RO-C6H4-CH=CH-COO-C6H4-CH=CH-CO-C6H3(OCH3)2meta-para is synthesized and studied with a view to understand and establish the relation between molecular structure and mesomorphism or mesomorphic behaviors. Novel homologous series consists of thirteen homologues (C1to C18). First five (C1to C5) homologues are nonmesogenic. Rest of the homologues (C6to C18) homologues is mesogenic. Monotropically smectogenic character appears from C6to C10homologue and C12to C18homologues are enantiotropically smectogenic. Nematogenic property is totally absent throughout a series. Textures of smectic phase are of the type smectic A or C. Transition curves of a phase diagram behaved in normal manner. Analytical, spectral and thermal data supports the molecular structures of homologues. Odd-even effect is observed for Sm-I/I-Sm transition curve. Thermal stability for smectic is 93.7 °C and the mesomorphic phase lengths from enantiotropic homologues for smectic from minimum to maximum is 6.0 °C to 28.0 °C at the C12and C18homologue respectively. Series is smectogenic without exhibition of nematic property. The group efficiency order on the basis of thermal stability is derived; from comparative study of present series and analogous series.

Combined experimental and computational investigations of rhodium-catalysed C - H functionalisation of pyrazoles with alkenes.

Detailed experimental and computational studies have been carried out on the oxidative coupling of the alkenes C2H3Y (Y=CO2Me (a), Ph (b), C(O)Me (c)) with 3-aryl-5-R-pyrazoles (R=Me (1 a), Ph (1 b), CF3 (1 c)) using a [Rh(MeCN)3Cp*][PF6]2/Cu(OAc)2⋅H2O catalyst system. In the reaction of methyl acrylate with 1 a, up to five products (2 aa–6 aa) were formed, including the trans monovinyl product, either complexed within a novel CuI dimer (2 aa) or as the free species (3 aa), and a divinyl species (6 aa); both 3 aa and 6 aa underwent cyclisation by an aza-Michael reaction to give fused heterocycles 4 aa and 5 aa, respectively. With styrene, only trans mono- and divinylation products were observed, whereas with methyl vinyl ketone, a stronger Michael acceptor, only cyclised oxidative coupling products were formed. Density functional theory calculations were performed to characterise the different migratory insertion and β-H transfer steps implicated in the reactions of 1 a with methyl acrylate and styrene. The calculations showed a clear kinetic preference for 2,1-insertion and the formation of trans vinyl products, consistent with the experimental results.

Synthesis of maresin 1 and (7S)-isomer

Maresin 1 (with the 7R carbon) and (7S)-maresin 1 were synthesized stereoselectively. The conjugated triene system was constructed by Pd-catalyzed coupling of the trans cis-dienylborane (the C10–C22 part) with the trans vinyl iodide corresponding to the C1–C9 part. The stereogenic centers at C7 and C14 were created by Ru-catalyzed asymmetric reduction of ketone and asymmetric epoxidation/kinetic resolution of the racemic alcohol, respectively.

Microstructural Evolution in Linear Low Density Polyethylene During Peroxide Modification: A Monte Carlo Simulation Study

A Monte Carlo (MC) simulation is performed on peroxide induced branching reactions in a linear low density polyethylene (LLDPE) melt processed with different dicumyl peroxide (DCP) concentrations at various processing times and temperatures. The MC simulation can successfully monitor the microstructural changes due to the induced long chain branching (LCB), decreased terminal double bonds, and increased trans vinyl bonds in LLDPE during peroxide modification. The induced structural changes are in good agreement with the experimental results obtained by rheometery and SEC analysis. The changes in the gel content, , and MWD as a result of the peroxide modification are also determined. The simulation results also reveal that the chemical mechanism by which the modification proceeded is closely related to the changes in concentrations of reactive vinyl species of the PE molecules. Moreover, the results indicate that the degree of induced LCB increases almost linearly with the DCP concentrations. The findings of this paper indicate that the MC simulation method is able to predict the suitable processing conditions needed for inducing desirable structural changes in a LLDPE.

Palladium‐Mediated Annulation of Vinyl Aziridines with Michael Acceptors: Stereocontrolled Synthesis of Substituted Pyrrolidines and Its Application in a Formal Synthesis of (−)‐α‐Kainic Acid

route to vinyl epoxides and vinyl aziridines via chiral sulfur ylides, we were keen to develop their potential in synthesis further. It had been reported that palladium-catalyzed reactions of vinyl epoxides and aziridines with doubly activated Michael acceptors gave tetrahydrofurans and pyrrolidines in good yield but usually with poor stereocontrol. However, related reactions with singly activated Michael acceptors were not effective. Nevertheless, we recognized that if we could find a way of coercing vinyl aziridines to react with singly activated enones/acrylates, and we were able to control stereochemistry in the annulation process, then we could potentially utilize this methodology in synthesis. Herein, we describe our success in simultaneously meeting these two significant challenges and also describe its application in a formal synthesis of ( )-a-kainic acid 1. Our initial efforts at promoting reaction between vinyl aziridine 2a and methyl vinyl ketone (MVK, A) using [Pd2(dba)3·CHCl3], (p-FC6H5)3P in THF (conditions employed by Yamamoto), however, were fruitless—we only observed decomposition. Using trimethylsilyl-substituted trans vinyl aziridine 2e, we now observed isomerization to a mixture of trans/cis aziridines (1:20). With this substrate, clearly the Pd was performing its role in generating the p-allyl palladium complex as this resulted in isomerization of the vinyl aziridine. However, the amide anion that was generated did not react with the enone. This result reinforced the observations by Yamamoto and Knight that doubly activated Michael acceptors were required to capture the relatively unreactive amide anion. We reasoned that ion pairing of the amide anion with the cationic Pd complex might compromise its reactivity, and that increased nucleophilicity should therefore be possible with an anionic Pd complex instead (Scheme 2).

Novel N9-arenethenyl purines as potent dual Src/Abl tyrosine kinase inhibitors

Novel N9-arenethenyl purines, optimized potent dual Src/Abl tyrosine kinase inhibitors, are described. The key structural feature is a trans vinyl linkage at N9 on the purine core which projects hydrophobic substituents into the selectivity pocket at the rear of the ATP site. Their synthesis was achieved through a Horner–Wadsworth–Emmons reaction of N9-phosphorylmethylpurines and substituted benzaldehydes or Heck reactions between 9-vinyl purines and aryl halides. Most compounds are potent inhibitors of both Src and Abl kinase, and several possess good oral bioavailability.

Hybrid Polymer Solar Cells from Highly Reactive Diethylzinc: MDMO–PPV versus P3HT

The degradation of poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-p-phenylene vinylene] (MDMO–PPV) during the processing of hybrid organic/inorganic bulk-heterojunction solar cells with zinc oxide (ZnO) from a molecular precursor as acceptor is reported. Upon addition of diethylzinc, the absorption spectrum of MDMO–PPV shifts to the blue, and hole transport through the polymer deteriorates dramatically, indicating a reduction of the conjugation length of the polymer backbone. To prevent polymer degradation through the breaking of trans vinyl bonds, regioregular poly(3-hexylthiophene) (P3HT) is introduced as the electron donor. This system of P3HT and precursor ZnO reveals an unchanged UV–vis absorption profile and zero-field hole mobility with respect to the pristine polymer as well as an improved photovoltaic performance with an estimated power conversion efficiency of 1.4% (AM1.5 global reference spectrum, 1 kW/m2).

Vinyl sulfide cyclized analogues of angiotensin II with high affinity and full agonist activity at the AT(1) receptor.

Vinyl sulfide cyclized analogues of the octapeptide angiotensin II that are structurally related to the cyclic disulfide agonist c[Hcy(3,5)]Ang II have been prepared. The synthesis relies on the reaction of the mercapto group of a cysteine residue in position 3 with the formyl group of allysine incorporated in position 5 of angiotensin II. A mixture of the cis and the trans isomers was formed, and these were separated and isolated by RP-HPLC. Thus, the three-atom CH(2)[bond]S[bond]S element of the AT(1) receptor agonist c[Hcy(3,5)]Ang II has been displaced by a bioisosteric three-atom S[bond]CH[double bond]CH element. A comparative conformational analysis of the 13-membered ring systems of c[Hcy(3,5)]Ang II and the 13-membered cyclic vinyl sulfides with cis and trans configuration, respectively, suggested that all three systems adopted very similar low-energy conformations. This similarity was also reflected in the bioactivity. Both of the compounds that contained the ring systems encompassing the cis or trans vinyl sulfide elements between positions 3 and 5 exhibited K(i) values less than 2 nM and exerted full agonism at the AT(1) receptor. In contrast, vinyl sulfide cyclization involving the amino acid residues 5 and 7 rendered inactive compounds. The cyclic vinyl sulfides that have agonist activity were both shown to possess low-energy conformers compatible with the previously proposed 3D model for the bioactive conformation of Ang II.

Energetics of Homogeneous Intermolecular Vinyl and Allyl Carbon−Hydrogen Bond Activation by the 16-Electron Coordinatively Unsaturated Organometallic Fragment [Tp‘Rh(CNCH2CMe3)

Reaction of the complex Tp‘Rh(CNneo)(CHCH2)Cl (neo = CH2CMe3, Tp‘ = hydridotris(3,5-dimethylpyrazolyl)borate) with Cp2ZrH2 leads to the formation of Tp‘Rh(CNneo)(CHCH2)H. This complex is also formed upon photolysis of a solution of Tp‘Rh(CNneo)(PhNCNneo) containing ethylene or by thermal reaction of Tp‘Rh(CNneo)(c-hexyl)H with ethylene. The vinyl hydride complex rearranges to the more stable η2-ethylene complex with a half-life of 8 h at 22 °C. Photolysis of a solution of Tp‘Rh(CNneo)(PhNCNneo) in liquid propylene produces the allylic activation product Tp‘Rh(CNneo)(CH2CHCH2)H, which rearranges (t1/2 = 3 days at 22 °C) to the η2-propylene complex. Allylic activation is also seen with isobutylene, but loss of olefin is observed at 22 °C in benzene solution to generate Tp‘Rh(CNneo)(Ph)H (t1/2 = 16.6 h). Photolysis of a tert-butylethylene solution of Tp‘Rh(CNneo)(PhNCNneo) produces the trans vinyl hydride complex, which loses tert-butylethylene to generate Tp‘Rh(CNneo)(Ph)H (t1/2 = 113 days at 22 °C). A comb...

Synthesis and preliminary evaluation of [ 123I]1-(4-cyanobenzyl)-4-[[( trans-iodopropen-2-yl)oxy]-methyl]piperidine: A novel high affinity sigma receptor radioligand for SPECT

1-(4-Cyanobenzyl)-4-[[( trans-iodopropen-2-yl)oxy]methyl]piperidine ( 2 ) has been synthesized as a novel iodinated ligand for sigma receptors. This new compound exhibited high affinity ( K i = 0.38 nM) for the sigma-1 receptor and selectivity for sigma-1 vs. sigma-2 receptors ( K i , σ−1 σ−2 = 0.02 ) using in vitro receptor binding assays. Moderate affinity for muscarinic M 1 ( K i = 322 nM) and M 2 ( K i = 178 nM) receptors and low affinity ( K i = 1,460 nM) for dopamine D 2 receptors was also noted. The lipophilicity of 2 (log P 7.5 = 3.24) is moderate, indicating that the ligand should readily cross the blood/brain barrier. The corresponding radioiodinated ligand, 123I- 2 , was synthesized from the appropriate trans vinyl tributylstannane precursor under acidic conditions using oxidative iododestannylation methods. HPLC purification provided the radioligand in yields ranging between 63 and 75% EOS ( n = 5) and with > 99% radiochemical purity and a specific activity > 77,000 MBq/μmol. Preliminary in vivo distribution and pharmacological blocking studies using 123I- 2 were performed in male Australian Albino Wistar rats. 123I- 2 exhibited good brain uptake (1.11 ± 0.14 %ID at 20 min PI) with no significant loss of radioactivity from the brain over the course of the study (4 h). The gross regional brain distribution of the radioligand showed highest uptake in the posterior cortex and frontal cortex, with slightly lower uptake in other brain regions examined. Most of the uptake of radioactivity in the brain, lung, heart, muscle, and kidney was prevented by pre-administration of compounds with affinity for sigma receptors, indicating the in vivo specificity of the ligand. In view of these results, 123I- 2 shows promise for the in vivo tomographic evaluation of sigma receptor densities.

Stereoselective alkyne insertion into a bridging hydride at a diiron centre: cis–trans isomerisation and metallacycle formation

Addition of the activated alkyne dimethyl acetylenedicarboxylate (dmad) to [Fe2(CO)4(µ-H)(µ-CO)(µ-PPh2)(µ-dppm)]1(dppm = Ph2PCH2PPh2) afforded the σ-η vinyl complex cis-[Fe2(CO)4{µ-C(CO2Me)CH(CO2Me)}(µ-PPh2)µ-dppm)]2. Crystallography showed that the insertion is stereo-selectively cis, with the phosphorus-containing ligands also adopting a cis configuration. Ultraviolet irradiation of 2 resulted in slow conversion into a second isomer, trans-[Fe2(CO)4{µ-C(CO2Me)CH-(CO2Me)}(µ-PPh2)(µ-dppm)]3, which still retains the cis arrangement of phosphines as shown by 31P NMR spectroscopy. This transformation is reversible, 3 slowly converting back into 2 at room temperature, a process which is accelerated upon heating. At temperatures of 80 °C, 2(and 3) was converted irreversibly into a third isomer [Fe2(CO4{C(CO2Me)CHC(OMe)O}(µ-PPh2)(µ-dppm)]4, containing a metallacyclic ring by virtue of metal co-ordination of an ester carbonyl. X-Ray crystallography revealed a trans vinyl orientation and a trans disposition of the phosphorus-containing groups.

EPR spectroscopic study of the reaction of aluminium and gallium atoms with acetylenes in a rotating cryostat

An electron paramagnetic resonance spectroscopic study of the reaction of ground-state Al atoms with acetylene in cyclohexane and adamantane at 77 K has demonstrated that transη1-aluminovinyl, AICHCH is the initial paramagnetic product and that it disappears on warming to 100 K. The spectra of cyclohexyl and 2-adamantyl, produced by hydrogen abstraction from the matrix, appear at this temperature. A second aluminium species is formed in adamantane with, magnetic parameters which indicate that it is not the π-complex η2-Al(CHCH) or aluminovinylidene, AlCCH2, but may be a hydrogen-bridged isomer. Substituted acetylenes give either a trans vinyl, a π-complex, or a polyvinyl while propyne gives a substantial yield of propargyl.Ga atoms and acetylene do not give an η1-gallovinyl but instead give a species, Ga(CHCH) with two magnetically equivalent H and C nuclei that is either a η2-, π- or σ-complex. Again in this system a significant yield of cyclohexyl and 2-adamantyl is produced byH-atom abstraction from the matrix.When the matrix is removed from samples of Al and acetylene an Al-substituted polyacetylene remains but in the case of Ga only the metal is left.

Spectroscopic properties and photodimerisation of water soluble poly(vinyl alcohol) modified with pendant (E)-2- [ p-formylstyryl]-3,4-dimethyl-thiazolium methyl sulphate groups: polymer and model chromophore studies

Preliminary results are presented on the spectroscopic properties and photocross-linking behaviour of a novel water-soluble poly(vinyl alcohol) modified with pendant styrylthiazolium groups and are compared with those of the model chromophore, (E)-2-[ p-formylstyryl]- 3,4-dimethyl-thiazolium methane sulphate in aqueous media. Second-order derivative UV-visible absorption spectra of both the modified photopolymer and the chromophore at high concentrations (greater than 5 × 10 −5 M) shows the presence of long-wavelength aggregates or dimers in the ground state. Fluorescence analysis of both the photopolymer and the chromophore is also consistent with the presence of long-wavelength-emitting dimers at high concentrations. On dilution the dimer emission decreases in intensity but remains evident together with that of stronger excimer and monomer emissions. Microsecond flash photolysis gives strong transient absorptions in the regions 300–400 and 400–500 nm. The former have maxima at 315 and 360 nm with the maxima of the latter at 405 and 460 nm and are associated with trans-cis isomerization or possible cation species involved in the [2+2] photocyclization reaction. Fourier transform IR analysis of the irradiated chromophore provided substantial evidence for the loss of the trans vinyl group and the formation of a substituted cyclobutane product due to a [2+2] photocycloaddition reaction. In aqueous solution, only trans-cis isomerism could be observed.

Entries into prostanoid models via the hydroboration of enol silyl ethers

The hydroboration of enol silyl ether ( 2), readily available from Stork's enone ( 1) with thexylborane gives the highly functionalized mixed organoborane ( 3). The remaining B-H bond of 3 can be used to hydroborate a terminal acetylene or a 1-bromoacetylene to give vinylboranes, which can then be utilized to introduce a trans vinyl group at C-12 of a prostanoid system in moderate yield. Although the yields are modest, the fact that 2 can be converted to the diprotected prostanoid system (see 19 or 21) in a one flask operation from readily available terminal acetylenes or 1-bromoacetylenes makes the methodology more attractive. In one attempt to use organoborane chemistry to introduce the cis-5-hepten-6-yl sidechain of the PGE 2; and related series 2 was converted to the exomethylene system 27 which was converted to 28 in 30% yield again in a single flask operation.

Microwave spectrum, conformation, and dipole moment of divinyl ether

The microwave spectrum of divinyl ether has been observed and a, b, and c type rotational transitions of one conformer assigned. This conformer has rotational constants closely related to the cis-trans planar form. The inertial defect and dipole moment reveal that it is not planar. This nonplanarity almost certainly results because of strong repulsion between the β hydrogen of the cis vinyl group and the α hydrogen of the trans vinyl group. The c type transitions are split 53 MHz by inversion tunneling. The dipole moment has been obtained from Stark effect measurements and is 0.782 debye.