3947-91-9

Upstream product

• 501-65-5 diphenyl acetylene 
• 5284-44-6 trans-1,2-dideuteriostilbene 
• 107-06-2 1,2-dichloro-ethane 
• 170653-12-0 ((CH₃)2CHO)2TiC₂(C₆H₅)2 
• 536-74-3 phenylacetylene 

Downstream Products

• 5284-44-6 trans-1,2-dideuteriostilbene 

Relevant academic research and scientific papers

Unimolecular reactions in isolated and collisional systems: Deuterium isotope effect in the photoisomerization of stilbene

The isomerization of t-stilbene (stilbene h12 ) and three deuterated derivatives has been studied in a supersonic expansion, the thermal gas phase, and solution.In the jet we find that almost all effect of full deuteration (stilbene d12 ) is produced by deuteration of the two ethylinic hydrogens only (stilbene d2 ).Complete deuteration of the phenyl rings (stilbene dlo ) has rather little influence on the decay of the jet-cooled molecule.Nonexponential decays are found at intermediate excess energies in the jet-cooled system, with the degree of nonexponentiality decreasing with increasing excess energy.The ordering of the decay rates observed in the jet is not consistent with previous RRKM calculations of the isomerization rates of stilbene h12 and d2.Using similar parameters the calculations consistently place the stilbene d2 and stilbene dlo curves in the wrong order.Our results suggest extensive but not complete vibrational relaxation in the isolated molecule.Vibrational redistribution rapidly becomes complete in the presence of buffer gas.In thermal samples the isomerization rates of stilbene h12 and stilbene d10 are identical over a wide range of solvents and temperatures.By contrast the isomerization rates in stilbene d2 and stilbene d12 are 1.4 and 1.5 times slower than in stilbene h12 Again, these ratios appear constant over a wide range of experimental conditions.

Fluorescence Quantum Yields of trans-Stilbene-d0 and -d2 in n-Hexane and n-Tetradecane. Medium and Deuterium Isotope Effects on Decay Processes

Fluorescence quantum yields of trans-stilbene-d0, t-d0, and α,α'-d2, t-d2 in n-hexane and in n-tetradecane are reported as a function of temperature.Together with literature lifetimes these are used to define radiative, kf, and radiationless, ktp, decay rate constants of trans-stilbene.The index of refraction dependence of kf is given by kf = kf0nx, where x = 1.65 +/- 0.08 and kf0 = 3.75 * 108s-1, the known radiative rate constant for jet-cooled isolated trans-stilbene in the gas-phase.Inclusion of the n-dependence of kf gives identical ktp's from fluorescence lifetime and quantum yield data.This eliminates small but opposite systematic errors in derived activation parameters for torsional relaxation that were previously based on fluorescence quantum yields or lifetimes, separately, by assuming a constant kf.Substitution of vinyl hydrogens with deuteria leads to a 50-60percent increase in the fluorescence quantum yields.The dependence of ktpd0/ktpd2 on T indicates that deuteriation increases ΔHtp by as much as 0.19 +/- 0.11 kcal/mol in n-hexane and that a more significant increase of 0.32 +/- 0.10 kcal/mol applies in n-tetradecane.

Ruthenium-Catalyzed E-Selective Partial Hydrogenation of Alkynes under Transfer-Hydrogenation Conditions using Paraformaldehyde as Hydrogen Source

E-alkenes were synthesized with up to 100 % E/Z selectivity via ruthenium-catalyzed partial hydrogenation of different aliphatic and aromatic alkynes under transfer-hydrogenation conditions. Paraformaldehyde as a safe, cheap and easily available solid hydrogen carrier was used for the first time as hydrogen source in the presence of water for transfer-hydrogenation of alkynes. Optimization reactions showed the best results for the commercially available binuclear [Ru(p-cymene)Cl2]2 complex as pre-catalyst in combination with 2,2-bis(diphenylphosphino)-1,1-binaphthyl (BINAP) as ligand (1 : 1 ratio per Ru monomer to ligand). Mechanistic investigations showed that the origin of E-selectivity in this reaction is the fast Z to E isomerization of the formed alkenes. Mild reaction conditions plus the use of cheap, easily available and safe materials as well as simple setup and inexpensive catalyst turn this protocol into a feasible and promising stereo complementary procedure to the well-known Z-selective Lindlar reduction in late-stage syntheses. This procedure can also be used for the production of deuterated alkenes simply using d2-paraformaldehyde and D2O mixtures.

Cobalt catalyzed stereodivergent semi-hydrogenation of alkynes using H2O as the hydrogen source

Cobalt-catalyzed stereodivergent semi-hydrogenation of internal alkynes to alkenes is developed. The reaction proceeded through transfer hydrogenation under mild conditions using a base metal CoI2 as the catalyst, and H2O/MeOH as the hydrogen source with Zn as the reductant. The E/Z-selectivity of the product could be switched by changing the solvent and by inclusion/exclusion of a bidentate phosphine ligand (dppe). This method provides a simple and cost effective pathway for the synthesis of 1,2-dideuterioalkenes.

Copper-catalysed, diboron-mediated: Cis -dideuterated semihydrogenation of alkynes with heavy water

Methods to incorporate deuterium atoms into organic molecules are valuable for the pharmaceutical industry. Here, we found that diboron reagents can efficiently mediate the transfer of two D atoms from heavy water directly onto alkynes through copper-catalysed cis-selective semihydrogenation. Avoiding the use of costly and flammable D2 gas, this safe and practical process can proceed with excellent chemoselectivity and stereoselectivity. Utilizing the present method as the key step, the formal asymmetric total synthesis of d2-deuterium-labeled cis-combretastatin A4 is demonstrated. Mechanistic studies suggest that monoborylation of alkynes is the key step for this semihydrogenation process.

Water as a Hydrogenating Agent: Stereodivergent Pd-Catalyzed Semihydrogenation of Alkynes

Palladium-catalyzed transfer semihydrogenation of alkynes using H2O as the hydrogen source and Mn as the reducing reagent is developed, affording cis- and trans-alkenes selectively under mild conditions. In addition, this method provides an efficient way to access various cis-1,2-dideuterioalkenes and trans-1,2-dideuterioalkenes by using D2O instead of H2O.

Ligand-controlled iridium-catalyzed semihydrogenation of alkynes with ethanol: highly stereoselective synthesis of E- and Z-alkenes

A ligand-controlled iridium-catalyzed semihydrogenation of alkynes to E- and Z-alkenes with ethanol was developed. Effective selectivity control was achieved by ligand regulation. The use of 1,2-bis(diphenylphosphino)ethane (DPPE) and 1,5-cyclooctadiene (COD) was critical for the stereoselective semihydrogenation of alkynes. The general applicability of this procedure was highlighted by the synthesis of more than 40 alkenes, with good stereoselectivities. The value of our approach in practical applications was investigated by studying the effects of pinosylvin and 4,4′-dihydroxystilbene (DHS) on zebrafish as a vertebrate model.

Mild, Selective Ru-Catalyzed Deuteration Using D2O as a Deuterium Source

A method for the selective deuteration of polyfunctional organic molecules using catalytic amounts of [RuCl2(PPh3)3] and D2O as a deuterium source is presented. Through variation of additives like CuI, KOH, and various amounts of zinc powder, orthogonal chemoselectivities in the deuteration process are observed. Mechanistic investigation indicates the presence of different, defined Ru-complexes under the given specific conditions.

Stereodivergent Alkyne Reduction by using Water as the Hydrogen Source

A homogeneous Pd-catalyzed stereodivergent reduction of alkynes to Z and E alkenes by using H2O as the H2 source is presented. Mediated by a diboron reagent, the transfer hydrogenation has been accomplished to yield the desired geometrical isomer by rational ligand selection. The switchable stereoselectivity achieved using simple phosphine ligands is generally excellent. D2O has also been used as a D2 source for synthesizing the corresponding deuterated olefins. Supported by a gram-scale synthesis, the reaction can easily be scaled up making it an efficient way to prepare alkenes commercially as well. Mechanistic studies suggest formation of H?PdL2?OAc as the crucial step leading to the presence of two pathways involving H?Pd?B(OR)2 and molecular H2 as active intermediates.

Direct and Stereospecific [3+2] Synthesis of Pyrrolidines from Simple Unactivated Alkenes

Pyrrolidines are important heterocyclic compounds with endless applications in organic synthesis, metal catalysis, and organocatalysis. Their potential as ligands for first-row transition-metal catalysts inspired a new method to access complex poly-heterocyclic pyrrolidines in one step from available materials. This fundamental step forward is based on the discovery of an essential organoaluminum promoter that engages unactivated and electron-rich olefins in intermolecular [3+2] cycloadditions.