19016-83-2Relevant academic research and scientific papers
Unprecedented Mechanism of an Organocatalytic Route to Conjugated Enynes with a Junction to Cyclic Nitronates
Streitferdt, Verena,Haindl, Michael H.,Hioe, Johnny,Morana, Fabio,Renzi, Polyssena,von Rekowski, Felicitas,Zimmermann, Alexander,Nardi, Martina,Zeitler, Kirsten,Gschwind, Ruth M.
, p. 328 - 337 (2018/11/23)
Conjugated enynes as well as cyclic nitronates are crucial building blocks for numerous natural products and pharmaceuticals. However, so far, no common and metal-free synthetic route to both conjugated enynes and cyclic nitronates has been reported. Herein, in situ NMR, labelling studies and theoretical calculations were combined to investigate the mechanism of the unusual triple bond formation towards conjugated enynes. Starting from nitroalkene dimers, first an isoxazolidine-2,5-diol derivative is formed as central intermediate. From this, enynes were generated by a combination of oxidation, dehydration, and retro 1,3-dipolar cycloaddition, whereas for nitronates a base induced intramolecular reorganization is proposed. While the product distribution could be controlled and high yields of nitronate were achieved, only medium to good yields for enynes were obtained due to polymerization losses. Nevertheless, we hope that these mechanistic investigations may provide a basis for further developments of organocatalytic or metal-free preparations of conjugated enynes and nitronates.
Rapid and efficient Pd-catalyzed sonogashira coupling of aryl chlorides
Huang, He,Liu, Hong,Jiang, Hualiang,Chen, Kaixian
, p. 6037 - 6040 (2008/12/21)
(Chemical Equation Presented) An efficient and effective microwave-assisted cross-coupling of terminal alkynes with various aryl chlorides including sterically hindered, electron-rich, electron-neutral, and electron-deficient aryl chloride is developed. It proceeds faster and generally gives good to excellent yields and also can be extended successfully to the Suzuki coupling and Buchwald-Hartwig amination, as well as the Heck coupling with inert aryl chlorides. The short reaction times and simple reaction conditions coupling with a broad substrate scope render this method particularly attractive for the efficient preparation of biologically and medicinally interesting molecules.
Integrated Chemical Process: One-Pot Double Elimination Method for Acetylenes
Orita, Akihiro,Yoshioka, Naonori,Struwe, Petra,Braier, Arnold,Beckmann, Anke,Otera, Junzo
, p. 1355 - 1363 (2007/10/03)
A novel one-pot process for synthesis of acetylenes has been achieved in which the following series of steps are integrated: addition of an α-anion of sulfone to aldehyde; trapping of the resulting adduct to incorporate a leaving group, and double elimination of this intermediate. Consolidation of Peterson elimination renders the process much simpler. This method provides a convenient and high-yielding access to a variety of enynes and polyynes as well as to functionally substituted aryl acetylenes containing halogen(s) or acetal groups, which are useful building blocks for aryl acetylene scaffolds. Iteration of the one-pot generation of acetylenic bonds provides a new metodology for the buildup of aryl acetylene skeletons.
Integrated chemical process. One-pot preparation of acetylenes by Peterson-sulfone elimination
Orita, Akihiro,Yoshioka, Naonori,Otera, Junzo
, p. 1023 - 1024 (2007/10/03)
Integration of silylation of α-sulfonyl carbanion, addition of the anion of the resulting α-silyl sulfone to aldehyde, Peterson elimination, and sulfone elimination leads to one-pot synthesis of acetylenes.
Electronic and Conformational Effects in the Photochemistry of α-Alkenyl-Substituted Vinyl Halides
Krijnen, Erik S.,Zuilhof, Han,Lodder, Gerrit
, p. 8139 - 8150 (2007/10/02)
The photochemical reactions in methanol of the vinylic halides 2-halo-1-phenyl-1,3-butadienes 1-3Z-X (β-halo-β-alkenylstyrenes) and 1-halo-1,2-diphenylethenes 4Z-X (α-halostilbenes), with X = Cl or Br, have been studied quantitatively.E/Z isomerization, dehydrohalogenation, nucleophilic substitution, a -halogen shift, a -hydrogen shift, and oxidation are observed as the primary reactions.No reductive dehalogenation products are formed.The efficiencies of product formation are dependent on the halogen used, the electron-donating capacity of the α-substituent, the ground state conformation of the starting material, and the wavelength of excitation.Apart from the photoinduced E/Z isomerization and the oxidation reaction typical for alkenes, product formation occurs exclusively via vinyl-cationic intermediates, which are formed upon photolytic cleavage of the carbon-halogen bond.These ionic species, or part of them, are present as vinyl cation/halide anion-pairs.
