Tetraethylammonium fluoroborate

The cyclization process can be promoted by using a single electron transfer mediator. Electron transfer from the mediator generates the carbonyl radical-ion away from the electrode surface so that cyclization can occur before there is opportunity for a second electron transfer. Thus reduction of 16, R = Me, in dimethyl-forraaraide at mercury in the presence of tetraethylammonium fluoroborate leads only to conversion of the ketone function to the secondaiy alcohol. However addition of a low concentration of N,N-dimethyl pyrrolidinium fluoroborate alters the course of reaction and the cyclized tertiary alcohol is now formed. This pyrrolidinium salt is reduced at -2.7 V vs. see at mercuiy to yield a complex DMP(Hg5) which is thought to act as a single electron transfer mediator [94]. Cyclization can... 

Acetophenone electrolyzed at room temp, in 1 2 trifluoroacetic aciV/-methylene chloride containing tetraethylammonium fluoroborate at a Pt-anode o-hydroxy-acetophenone. Y 85%. F. e., also ar. acylaminatioii (cf. Synth. Meth. 29, 334), s. Y.-H. So, J.Y. Becker, and L.L. Miller, Chem. Common. 1975, 262. 

Jacobsen and Pedersen153 confirmed the generation of benzoxonium ion 126 by treatment of compound 125 with triphenylmethyl fluoroborate in acetonitrile, but they treated it with tetraethylammonium bromide, obtaining a 3 2 mixture of the a and /3 anomers of methyl 2,5-di-0-benzoyl-3-bromo-3-deoxy-D-xylofuranoside (134) in a yield of 74%. This mixture could be anomerized to give the pure )8 anomer (overall yield 60%) by treatment with hydrogen bromide followed by the action of methanol. 

Harris and co-workers [79] studied seven systems and found their best results were with either o-diaminobenzene/LiC104 or p-diaminobenzene/tetraethylammonium tetra-fluoroborate (C8H20B4N) and they could improve the interfadal shear strength of Enka HTA-3000 by 46% over the value for the untreated fiber. 

A mixture of (S)-(+)-2-octanol and triethylamine in methylene chloride added dropwise at -60° under argon to a suspension of 3-ethyl-2-fluorobenzothiazolium fluoroborate in dry methylene chloride with stirring, which is continued an additional hr. at -60 to -45°, a soln. of Nal in acetone added at -45°, and gradually warmed to room temp, during 3 hrs. (R)-(-)-2-iodooctane. Y 87%. F. e., also bromides and chlorides, s. K. Hojo and T. Mukaiyama, Chem. Lett. 1976, 619 chlorides with 2-chloro-3-ethylbenzoxazolium fluoroborate in the presence of tetraethylammonium chloride s. ibid. 1977, 383. 

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