Effect of a Substituent in the Benzene Ring upon the Kinetics of Acid-Catalyzed Hydrolysis of exo-2-Norbornyl Phenyl Ether.
摘要:
The rate constants of hydrolysis for exo-2-norbornyl phenyl ether without substituent and with p-Me, p-Ac, m-CN, p-CN or p-NO2 group in the benzene ring were measured in concentrated perchloric acid solutions spectrophotometrically and/or by capillary GC. The effect of the substituent on the rate constants and other kinetic parameters of hydrolysis is small. The parameters are in agreement with the A-1 mechanism. The ether oxygen of the exo-epimer is much more basic than that of the endo-epimer (pK(a,exo)-pK(a,endo)approximate to 2), which causes a greater part of the exo/endo rate ratio than do the initial state energies and rate constants of the rate limiting stage, i.e. of the formation of the norbornyl cation and the substituted phenol.
Iron(III) Triflimide as a Catalytic Substitute for Gold(I) in Hydroaddition Reactions to Unsaturated Carbon-Carbon Bonds
作者:Jose R. Cabrero-Antonino、Antonio Leyva-Pérez、Avelino Corma
DOI:10.1002/chem.201300386
日期:2013.6.24
In this work it is shown that iron(III) and gold(I) triflimide efficiently catalyze the hydroaddition of a wide array of nucleophiles including water, alcohols, thiols, amines, alkynes, and alkenes to multiple CC bonds. The study of the catalytic activity and selectivity of iron(III), gold(I), and Brønsted triflimides has unveiled that iron(III) triflimide [Fe(NTf2)3] is a robust catalyst under heating
在这项工作中表明,三氟甲磺酸铁(III)和金(I)可有效催化多种亲核试剂(包括水,醇,硫醇,胺,炔烃和烯烃)加氢成多个CC键。铁(III),金(I)和布朗斯台德三氟甲酸酯的催化活性和选择性的研究表明,三氟甲铁(III)[Fe(NTf 2)3 ]在加热条件下是一种坚固的催化剂,而金(I) )甚至由PPh 3稳定的三氟甲酰亚胺在80°C时容易分解并释放出三氟乙二酸(HNTf 2),该三氟乙二酸可催化相应的反应,如原位19 F,15 N和311 H NMR光谱。此处给出的结果表明,两种催化剂类型均具有弱点和优势,并且彼此互补。三氟化铁(III)可以替代三氟化金(I),作为不饱和碳-碳键加氢反应的催化剂。
REACTION OF<i>exo</i>-2-NORBORNYL AND 1-ADAMANTYL<i>p</i>-TOLUENESULFONATES WITH SODIUM PHENOXIDE IN TETRAHYDROFURAN. IONIZATION OF THE SUBSTRATES UNDER “APPARENTLY-S<sub>N</sub>2” CONDITIONS
exo-2-Norbornyl and 1-adamantyl tosylates react with sodiumphenoxide in tetrahydrofuran via ionization, most probably through a cyclic transition state. The results call for attention in interpreting substitution reactions under “apparently-SN2” conditions.
Hidden Brønsted Acid Catalysis: Pathways of Accidental or Deliberate Generation of Triflic Acid from Metal Triflates
作者:Tuan Thanh Dang、Florian Boeck、Lukas Hintermann
DOI:10.1021/jo201631x
日期:2011.11.18
The generation of a hidden Bronsted acid as a true catalytic species in hydroalkoxylation reactions from metal precatalysts has been clarified in case studies. The mechanism of triflic acid (CF3SO3H or HOTf) generation starting either from AgOTf in 1,2-dichloroethane (DCE) or from a Cp*RuCl2/AgOTf/phosphane combination in toluene has been elucidated. The deliberate and controlled generation of HOTf from AgOTf and cocatalytic amounts of tert-butyl chloride in the cold or from AgOTf in DCE at elevated temperatures results in a hidden Bronsted acid catalyst useful for mechanistic control experiments or for synthetic applications.