32569-87-2Relevant academic research and scientific papers
Dimerization of two alkyne units: Model studies, intermediate trapping experiments, and kinetic studies
Fabig, Sven,Haberhauer, Gebhard,Gleiter, Rolf
, p. 1833 - 1843 (2015)
By means of high level quantum chemical calculations (B2PLYPD and CCSD(T)), the dimerization of alkynes substituted with different groups such as F, Cl, OH, SH, NH2, and CN to the corresponding diradicals and dicarbenes was investigated. We found that in case of monosubstituted alkynes the formation of a bond at the nonsubstituted carbon centers is favored in general. Furthermore, substituents attached to the reacting centers reduce the activation energies and the reaction energies with increasing electronegativity of the substituent (F > OH > NH2, Cl > SH, H, CN). This effect was explained by a stabilizing hyperconjugative interaction between the σ orbitals of the carbon-substituent bond and the occupied antibonding linear combination of the radical centers. The formation of dicarbenes is only found if strong π donors like NH2 and OH as substituents are attached to the carbene centers. The extension of the model calculations to substituted phenylacetylenes (Ph-C=C-Y) predicts a similar reactivity of the phenylacetylenes: F > OCH3 > Cl > H. Trapping experiments of the proposed cyclobutadiene intermediates using maleic anhydride as dienophile as well as kinetic studies confirm the calculations. In the case of phenylmethoxyacetylene (Ph-C=C-OCH3) the good yield of the corresponding cycloaddition product makes this cyclization reaction attractive for a synthetic route to cyclohexadiene derivatives from alkynes.
CuII-Catalyzed Oxidative Formation of 5-Alkynyltriazoles
Liu, Peiye,Brassard, Christopher J.,Lee, Justin P.,Zhu, Lei
supporting information, p. 380 - 390 (2020/01/24)
In an alcoholic solvent under the catalysis of Cu(OAc)2?H2O, organic azide and terminal alkyne could oxidatively couple to afford 5-alkynyl-1,2,3-triazole (alkynyltriazole) at room temperature under an atmosphere of O2 in a few hours. The involvement of 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) is essential, without which the redox neutral coupling instead proceeds to produce 5-H-1,2,3-triazole (protiotriazole) as the major product. Therefore, DBN switches the redox neutral coupling between terminal alkyne and organic azide, the copper-catalyzed “click” reaction to afford protiotriazole, to an oxidation reaction that results in alkynyltriazole. The organic base DBN is effective in accelerating the copper(II)-catalyzed oxidation of terminal alkyne or copper(I) acetylide, which is intercepted by an organic azide to produce alkynyltriazole. The proposed mechanistic model suggests that the selectivity between alkynyl- and protiotriazole, and other acetylide or triazolide oxidation products is determined by the competition between copper(I)-catalyzed redox neutral cycloaddition and copper(II)/O2-mediated acetylide oxidation after the formation of copper(I) acetylide.
Benign catalysis with zinc: Atom-economical and divergent synthesis of nitrogen heterocycles by formal [3 + 2] annulation of isoxazoles with ynol ethers
Zhu, Xin-Qi,Yuan, Han,Sun, Qing,Zhou, Bo,Han, Xiao-Qin,Zhang, Zhi-Xin,Lu, Xin,Ye, Long-Wu
supporting information, p. 4287 - 4291 (2018/09/29)
Herein, we disclose an efficient zinc-catalyzed formal [3 + 2] annulation of isoxazoles with ynol ethers under exceptionally mild reaction conditions, leading to the atom-economical and divergent synthesis of 2-alkoxyl 1H-pyrroles and 3H-pyrroles, respect
Transition-metal-free synthesis of ynol ethers and thioynol ethers via displacement at sp Centers: A revised mechanistic pathway
Gray, Vincent James,Cuthbertson, James,Wilden, Jonathan D.
, p. 5869 - 5874 (2014/07/08)
We present here valuable extensions to our previous work in preparing highly functionalized, heteroatom-substituted alkynes via displacement at an sp center. Our results show that a wide range of ynol ethers can be prepared by the same methodology and that the same protocol can be applied to the synthesis of synthetically useful thioynol ethers. We also present new observations that have led us to revise our original hypothesis in favor of a pathway involving radical intermediates.
