70659-93-7Relevant articles and documents
Nucleophilic Fluorination with KF Catalyzed by 18-Crown-6 and Bulky Diols: A Theoretical and Experimental Study
Silva, Samuel L.,Valle, Marcelo S.,Pliego, Josefredo R.
, p. 15457 - 15465 (2020/12/23)
The activation of potassium fluoride for nucleophilic fluorination of alkyl halides is an important challenge because of the high lattice energy of this salt and its low solubility in many polar aprotic solvents. Crown ethers have been used for increasing the solubilization of KF during several decades. Nevertheless, these macrocycles are not enough to produce a high reaction rate. In this work, theoretical methods were used for designing a synergic combination of bulky diols with crown ethers able to accelerate this kind of reaction. The calculations have predicted that the bulky diol 1,4-Bis(2-hydroxy-2-propyl)benzene, which has distant hydroxyl groups, is able to catalyze nucleophilic fluorination in combination with 18-crown-6 via two hydrogen bonds to the SN2 transition state. Experimental studies following the theoretical predictions have confirmed the catalytic effect and the estimated kinetic data point out that the bulky diol at 1 mol L-1 in combination with 18-crown-6 is able to produce an 18-fold increase in the reaction rate in relation to crown ether catalysis only. The reaction produces 46% yield of fluorination after 24 h at moderate temperature of 82 °C, with minimal formation of the side elimination product. Thus, this work presents an improved method for fluorination with KF salt.
Competing 1,3- and 1,2-hydrogen shifts in gaseous fluoropropyl cations
Shaler, Thomas A.,Borchardt, Dan,Morton, Thomas Hellman
, p. 7907 - 7913 (2007/10/03)
An initial 1,2-hydrogen shift versus a 1,3-deuterium shift in emerging FCD2CH2CH2+ ions lead to differing patterns of deuteration in the neutral products that are recovered following reaction with a Bronsted base. Transient dideuterated fluoropropyl ions have been produced in [C3H4D2F+ PhO·] ion-neutral complexes by 70 eV electron impact on FCD2CH2CH2OPh and the resulting fluoropropenes collected in a specially designed electron bombardment flow (EBFlow) reactor. Under these conditions ion-neutral complexes greatly predominate over free fluoropropyl cations. Free ions afford products that are easily distinguished from those that result from ion-neutral complexes, in which the phenoxy radical serves as the Bronsted base. 1,2-Hydrogen shift yields ions containing CH3-groups, while the ions from 1,3-shift have CDH2-groups. Allyl fluoride and 1-fluoropropene arise from ion-neutral complexes, and the extent and positions of deuteration have been determined by 19F NMR. Six deuterated variants of trans-1-fluoropropene can be resolved in the NMR spectrum of the neutral products collected from the EBFlow. The proportions of CH3 and CDH2 measured by integration imply a branching ratio of 1,2-hydrogen versus 1,3-deuterium shift of approximately 94:6.
