598-23-2Relevant articles and documents
Synthesis of the complete carbocyclic skeleton of vinigrol
Gentric, Lionel,Hanna, Issam,Ricard, Louis
, p. 1139 - 1142 (2003)
(Matrix presented) An efficient entry to the fully elaborated skeleton of vinigrol is described. The installation of the desired stereochemistry at C(12) and the construction of the eight-membered ring were achieved in one operation by a remarkably facile anionic oxy-Cope rearrangement of Z-isopropenyl isomer 24.
THERMAL ISOMERIZATION OF 3,3-DIMETHYLCYCLOPROPENE UNDER ADIABATIC-COMPRESSION CONDITIONS
Kuptsova, T. S.,Buravtsev, N. N.,Chernyak, N. Ya.,Shapiro, E. A.,Kolbanovskii, Yu. A.,Nefedov, O. M.
, p. 1845 - 1847 (1989)
The thermal isomerization of 3,3-dimethylcyclopropene under adiabatic-compression conditions at 660-850 K occurs in two independent directions with the formation of isopropylacetylene and isoprene; kinetic parameters for each of these routes were obtained.The formation of products of the gem-dimethylvinylcyclopropanation of olefins during their copyrolysis with 3,3-dimethylcyclopropene is not observed, apparently because of the occurrence of isomerization of 3,3-dimethylcyclopropene in the gas phase at 660-850 K without the participation of gem- dimethylvinylcarbene.
From the lindlar catalyst to supported ligand-modified palladium nanoparticles: Selectivity patterns and accessibility constraints in the continuous-flow three-phase hydrogenation of acetylenic compounds
Vile, Gianvito,Almora-Barrios, Neyvis,Mitchell, Sharon,Lopez, Nuria,Perez-Ramirez, Javier
, p. 5926 - 5937 (2014/05/20)
Site modification and isolation through selective poisoning comprise an effective strategy to enhance the selectivity of palladium catalysts in the partial hydrogenation of triple bonds in acetylenic compounds. The recent emergence of supported hybrid materials matching the stereo- and chemoselectivity of the classical Lindlar catalyst holds promise to revolutionize palladium-catalyzed hydrogenations, and will benefit from an in-depth understanding of these new materials. In this work, we compare the performance of bare, lead-poisoned, and ligand-modified palladium catalysts in the hydrogenation of diverse alkynes. Catalytic tests, conducted in a continuous-flow three-phase reactor, coupled with theoretical calculations and characterization methods, enable elucidation of the structural origins of the observed selectivity patterns. Distinctions in the catalytic performance are correlated with the relative accessibility of the active site to the organic substrate, and with the adsorption configuration and strength, depending on the ensemble size and surface potentials. This explains the role of the ligand in the colloidally prepared catalysts in promoting superior performance in the hydrogenation of terminal and internal alkynes, and short-chain alkynols. In contrast, the greater accessibility of the active surface of the Pd-Pb alloy and the absence of polar groups are shown to be favorable in the conversion of alkynes containing long aliphatic chains and/or ketone groups. These findings provide detailed insights for the advanced design of supported nanostructured catalysts. Hybrid nanocatalysts: The classical Lindlar and the newly developed NanoSelectTM catalysts are confronted in the semi-hydrogenation of alkynes (see figure). Systematic testing under continuous-flow three-phase conditions, coupled with detailed characterization analyses and molecular simulations, enable the understanding of the structure of the catalysts and the associated activity and selectivity patterns for a wide range of acetylenic compounds.
A straightforward synthesis of alkenyl nonaflates from carbonyl compounds using nonafluorobutane-1-sulfonyl fluoride in combination with phosphazene bases
Vogel, Michael A. K.,Stark, Christian B. W.,Lyapkalo, Ilya M.
, p. 2907 - 2911 (2008/02/13)
An α-deprotonation of carbonyl compounds with phosphazene bases in the presence of the internal quenching reagent, nonafluorobutane-1-sulfonyl fluoride furnishes the corresponding alkenyl nonaflates. The new general method provides high yields of alkenyl nonaflates from aldehydes and cyclic ketones. However, it is not applicable to acyclic ketones whose nonaflate derivatives undergo fast E2 elimination to give alkynes. Successful synthesis of nonaflates from aldehydes requires carefully controlled reaction conditions to avoid the subsequent elimination to alkynes. A kinetic control enables high regioselectivities in favor of least substituted nonaflate regioisomers derived from cyclic ketones and modest Z-selectivities of alkenyl nonaflates derived from aldehydes. A new efficient protocol for highly selective removal of perfluorosulfolane admixture from technical nonafluorobutane-1-sulfonyl fluoride by basic hydrolysis is described. Georg Thieme Verlag Stuttgart.
A general and versatile method for C-C cross-coupling synthesis of conjugated enynes: One-pot sequence starting from carbonyl compounds
Lyapkalo, Ilya M.,Vogel, Michael A. K.
, p. 4019 - 4023 (2007/10/03)
(Chemical Equation Presented) Ultimate coupling partners: Widely available enolizable aldehydes and ketones undergo Sonogashira cross-coupling with other carbonyl compounds to give conjugated enynes in a newly devised general method (see scheme; NfF = nonafluorobutane-1-sulfonyl fluoride). The synthetic protocol comprises at least four operating steps, which are carried out in one pot using common reagents, catalysts, and additives.
Process for the preparation of cyclopropylacetylene
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Page column 15-16, 17-18, (2008/06/13)
The present invention relates generally to novel methods for the preparation of cyclopropylacetylene which is an essential reagent in the asymmetric synthesis of (S)-6-chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one; a useful human immunodeficiency virus (HIV) reverse transcriptase inhibitor with superior anti-retroviral activity. In the process, for example, cyclopropane carboxaldehyde is alkylated to form 1,1,1-trichloro-2-cyclopropyl-ethanol; which in turn undergoes elimination to form 1,1-dichloro-2-cyclopropyl-ethene; which in turn undergoes elimination to form cyclopropyl acetylene.
Silylformylation of chiral 1-alkynes, catalysed by solvated rhodium atoms
Aronica, Laura Antonella,Terreni, Silvia,Caporusso, Anna Maria,Salvadori, Piero
, p. 4321 - 4329 (2007/10/03)
Solvated rhodium atoms, prepared by the metal vapour synthesis technique, promote the silylformylation reaction of variously substituted alkynes R1R2CH(CH2)nC≡CH, with catalytic activities comparable with and even higher than more common species such as Rh4(CO)12. Z-Silylalkenals are exclusively formed in high yields (60-95%) indicating syn addition both of CO and of the silane (Me2PhSiH) to the triple bond. The chemoselectivity of the process (silylformylation vs. hydrosilylation) is highly affected by the amount of catalyst employed (mmol of Rh species with respect to the alkyne reagent), by the steric requirements of the acetylenic substrates and by the hydrosilane/alkyne molar ratio. When optically active acetylenes are treated in the presence of Me2PhSiH under carbon monoxide pressure, the silylformylation reaction occurs with total retention of stereochemistry of the stereogenic centre, even if it is at the α-position of the unsaturated moiety, to afford enantiomerically enriched β-silylalkenals.
Synthesis, properties, oxidation, and electrochemistry of 1,2- dichalcogenins
Block, Eric,Birringer, Marc,Deorazio, Russell,Fabian, Juergen,Glass, Richard S.,Guo, Chuangxing,He, Chunhong,Lorance, Edward,Qian, Quangsheng,Schroeder, T. Benjamin,Shan, Zhixing,Thiruvazhi, Mohan,Wilson, George S.,Zhang, Xing
, p. 5052 - 5064 (2007/10/03)
Syntheses are presented of the 1,2-dichalcogenins: 1,2-dithiin, 1,2- diselenin, and 2-selenathiin, both substituted and unsubstituted. 1,2-Dithiin and 1,2-diselenin are prepared by reaction of PhCH2XNa (X = S or Se) with 1,4-bis(trimethylsilyl)-1,3-butadiyne followed by reductive cleavage and oxidation. 2-Selenathiin is similarly prepared using a mixture of PhCH2SeNa and PhCH2SNa. Reaction of titanacyclopentadienes with (SCN)2 or (SeCN)2 followed by bis(thiocyanate) or bis(selenocyanate) cyclization affords substituted 1,2-dithiins or 1,2-diselenins, respectively. With S2Cl2, 1,2- dithiins are directly formed from titanacyclopentadienes. Oxidation of 1,2- dithiins and 1,2-diselenins gives the corresponding 1-oxide and, with 1,2- dithiins and excess oxidant, 1,1-dioxides; oxidation of 2-selenathiin gives the 2-oxide. Electrochemical oxidation of 1,2-dichalcogenins, which have a twisted geometry, affords planar radical cations by an EC mechanism. One- electron AlCl3 oxidation of 3,6-diphenyl-1,2-dithiin gives the corresponding radical cation, characterized by EPR spectroscopy. Theoretical calculations result in a flattened structure for the 1,2-dithiin radical cation and a fully planar structure for the 1,2-diselenin radical cation. The 77Se NMR chemical shifts of 1,2-diselenin are characteristically high-field-shifted with respect to open chain diselenides in good agreement with results of GIAO-DFT calculations based on MP2 and DFT optimum geometries.
A new and practical synthesis of vinyl dichlorides via a non-Wittig-type approach
Wang, Zhe,Campagna, Silvio,Xu, Guoyou,Pierce, Michael E.,Fortunak, Joseph M.,Confalone, Pat N.
, p. 4007 - 4009 (2007/10/03)
A practical approach for the conversion of aldehydes to vinyl dichlorides has been developed. These are three-step, one-pot reactions involving the formation of trichlorocarbinol by treatment of aldehydes with trichloroacetic acid and sodium trichloroacetate followed by in situ protection and elimination reactions to form the desired vinyl dichlorides in 85 to 95% yields. (C) 2000 Dupont Pharmaceuticals Company.
In-plane vinylic S(N)2 substitution and intramolecular β elimination of β-alkylvinyl(chloro)-λ3-iodanes
Okuyama, Tadashi,Takino, Tomoki,Sato, Koichi,Ochiai, Masahito
, p. 2275 - 2282 (2007/10/03)
The reactions of four (E)-β-alkylvinyl(phenyl)iodonium salts with chloride ion were examined in acetonitrile and in several other solvents at 25°C. The β-methyl-, β-octyl-, and β-isopropyl-substituted iodonium salts undergo competitive bimolecular nucleophilic substitution to form the corresponding (Z)-1-chloro-1-alkene with inversion of configuration at the vinylic carbon and elimination to form the 1-alkyne. The β-tert-butyl-substituted iodonium salt affords only the products of the elimination reaction. The UV absorption spectra of the reactants show the rapid coversion of chloride and iodonium ions to an equilibrium mixture of the corresponding chloro-λ3-iodane, with an association constant of 5600-7600 mol-1 dm3. A kinetic analysis shows that most of the substitution and elimination products form from reaction of the λ3-iodane. Evidence is presented that the substitution reaction proceeds by a concerted bimolecular S(N)2 mechanism and that the elimination reaction proceeds by a unimolecular reaction mechanism with intramolecular transfer of the β-proton to the leaving group.
