Generation and oligomerization of bicyclo[2.2.2]octyne and properties of tris(bicyclo[2.2.2]octeno)benzene obtained from the linear trimer
摘要:
Reaction of 2,3-dibromobicyclo[2.2.2]oct-2-ene (10) with n-butyllithium in THF at -78-degrees-C affords a series of oligomeric dibromides 11 (n = 2-5), which are composed of linearly bonded bicyclo[2.2.2]oct-2-ene units. A trapping experiment indicated that the reaction proceeds via formation of a highly strained acetylene, bicyclo[2.2.2]octyne (18), as a reactive intermediate. Upon treatment with sodium naphthalenide, the trimer 11 (n = 3) reductively cyclizes to tris(bicyclo[2.2.2]octeno)benzene (12) in high yield. The benzene 12 exhibits a reversible oxidation wave at +1.25 V vs Ag/AgNO3 on cyclic voltammetry and gives a stable cation radical 12.+ electrolytically or by oxidation with H2SO4 in air. In FSO3H, 12 is 100% protonated to give the arenium ion 22. The results of variable-temperature C-13 NMR study indicate that the activation energy for the intermolecular proton transfer of 22 is lower than that for the hexamethylbenzenium ion (23). The rate of intramolecular hydrogen migration is also much faster in 22. These results are in agreement with the relative instability of 22 (pK(AH+) -10.2) as compared with 23 (pK(AH+) -9.01).
Generation and oligomerization of bicyclo[2.2.2]octyne and properties of tris(bicyclo[2.2.2]octeno)benzene obtained from the linear trimer
摘要:
Reaction of 2,3-dibromobicyclo[2.2.2]oct-2-ene (10) with n-butyllithium in THF at -78-degrees-C affords a series of oligomeric dibromides 11 (n = 2-5), which are composed of linearly bonded bicyclo[2.2.2]oct-2-ene units. A trapping experiment indicated that the reaction proceeds via formation of a highly strained acetylene, bicyclo[2.2.2]octyne (18), as a reactive intermediate. Upon treatment with sodium naphthalenide, the trimer 11 (n = 3) reductively cyclizes to tris(bicyclo[2.2.2]octeno)benzene (12) in high yield. The benzene 12 exhibits a reversible oxidation wave at +1.25 V vs Ag/AgNO3 on cyclic voltammetry and gives a stable cation radical 12.+ electrolytically or by oxidation with H2SO4 in air. In FSO3H, 12 is 100% protonated to give the arenium ion 22. The results of variable-temperature C-13 NMR study indicate that the activation energy for the intermolecular proton transfer of 22 is lower than that for the hexamethylbenzenium ion (23). The rate of intramolecular hydrogen migration is also much faster in 22. These results are in agreement with the relative instability of 22 (pK(AH+) -10.2) as compared with 23 (pK(AH+) -9.01).
Nickel‐Catalyzed Conversion of Enol Triflates into Alkenyl Halides
作者:Julie L. Hofstra、Kelsey E. Poremba、Alex M. Shimozono、Sarah E. Reisman
DOI:10.1002/anie.201906815
日期:2019.10.14
A Ni-catalyzed halogenation of enol triflates was developed and it enables the synthesis of a broad range of alkenyl iodides, bromides, and chlorides under mild reaction conditions. The reaction utilizes inexpensive, bench-stable Ni(OAc)2 ⋅4 H2 O as a precatalyst and proceeds at room temperature in the presence of sub-stoichiometric Zn and either 1,5-cyclooctadiene or 4-(N,N-dimethylamino)pyridine
开发了镍催化的烯醇三氟甲磺酸酯卤化反应,能够在温和的反应条件下合成多种烯基碘化物、溴化物和氯化物。该反应使用廉价、实验室稳定的 Ni(OAc)2·4 H2 O 作为预催化剂,并在亚化学计量的 Zn 和 1,5-环辛二烯或 4-(N,N-二甲基氨基) 存在下在室温下进行吡啶。
Synthesis, Structure, and Dynamic Behavior of Cyclopentadienyl-Lithium, -Sodium, and -Potassium Annelated with Bicyclo[2.2.2]octene Units: A Systematic Study on Site Exchange of Alkali Metals on a Cyclopentadienyl Ring in Tetrahydrofuran
kcal mol(-)(1) for M = Na; 115.4 kcal mol(-)(1) for M = K). These values should be compensated for by a decrease in the solvation energies for the metal ions with increasing size, as exemplified by the calculated solvation energy for M(+)(Me(2)O)(4), which serves as a model for metal ions solvated with four molecules of THF (-122.9 kcal mol(-)(1) for M = Li; -94.7 kcal mol(-)(1) for M = Na; -67.7 kcal
Reaction of 2,3-dibromobicyclo[2.2.2]oct-2-ene (10) with n-butyllithium in THF at -78-degrees-C affords a series of oligomeric dibromides 11 (n = 2-5), which are composed of linearly bonded bicyclo[2.2.2]oct-2-ene units. A trapping experiment indicated that the reaction proceeds via formation of a highly strained acetylene, bicyclo[2.2.2]octyne (18), as a reactive intermediate. Upon treatment with sodium naphthalenide, the trimer 11 (n = 3) reductively cyclizes to tris(bicyclo[2.2.2]octeno)benzene (12) in high yield. The benzene 12 exhibits a reversible oxidation wave at +1.25 V vs Ag/AgNO3 on cyclic voltammetry and gives a stable cation radical 12.+ electrolytically or by oxidation with H2SO4 in air. In FSO3H, 12 is 100% protonated to give the arenium ion 22. The results of variable-temperature C-13 NMR study indicate that the activation energy for the intermolecular proton transfer of 22 is lower than that for the hexamethylbenzenium ion (23). The rate of intramolecular hydrogen migration is also much faster in 22. These results are in agreement with the relative instability of 22 (pK(AH+) -10.2) as compared with 23 (pK(AH+) -9.01).