Triethyloxonium fluoborate

TRIETHYLOXONIUM FLUOBORATE (Ozonium compounds, triethylozonium tetrafluoroborate) 

The checkers obtained boron fluoride etherate and epichloro-hydrin from Eastman Organic Chemicals and redistilled each through a 23-cm. Vigreux column immediately before use. 

It is convenient to measure the liquids with syringes using the densities epichlorohydrin df 1.179 boron fluoride etherate, f 1.125. 

Triethyloxonium fluoborate is very hygroscopic. It should be stored in a tightly closed screw-cap bottle at 0-5° and should be used within a few days of the time it is made. It should be weighed and transferred in a dry box. It can be stored indefinitely under ether or at —80°. 

The procedure used is essentially that described by Meerwein and co-workers. 2, s The salt also has been prepared from ethyl fluoride and boron fluoride etherate, and from silver fluoborate, ethyl bromide, and ether.4 

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The great utility of the trialkyloxonium salts is illustrated by the fact that high yields of esters are obtained using reagent which has been stored for up to 6 months under the submitters conditions (Notes 1 and 12). Thus either trimethyl- or triethyloxonium fluoborate can be prepared in quantity, stored, and used for esterification as required. 

Furthermore, recent studies indicate that esterifications involving triethyloxonium fluoborate are often very rapid. For example, subsequent to the checking of this procedure the submitters ha ve found that the reaction time of Part A may be shortened from 16-24 hours to 0.5 hour with no decrease in yield. The longer reaction time is still recommended for esterifications involving the trimethyl salt, such as that of Part B, because of the heterogeneous nature of the reaction mixture in these cases. 

Hydroxypyridone 337 by triethyloxonium fluoborate was transformed to ether 338 that resisted nucleophilic reactions (76IJB400). Such reactions were possible, however, in the case of pyridone 192a through chloro compound 384. Nucleophilic displacement of triflate 28 resulted in the formation of iodide 29a as the major product (94TL393). 

Trimethyloxonium fluoborate is less hygroscopic and keeps better than triethyloxonium fluoborate, but it should be stored at 0-5° in a tightly closed screw-cap bottle.2 So stored, it can be kept at least a few weeks. 

This facile preparation is suitable for preparation of larger amounts of salt Like triethyloxonium fluoborate,2 trimethyloxonium fluoborate is a potent alkylating agent. In comparison with trimethyloxonium 2,4,6-trinitrobenzenesulfonate,5trimethyl-oxonium fluoborate is easier to make but does not keep quite as well on storage. 

Like triethyloxonium fluoborate,12 trimethyloxonium 2,4,6-trinitrobenzenesulfonate is a potent alkylating agent. Tri-... 

Freshly prepared triethyloxonium fluoborate (170 g., 0,90 mole) is dissolved in 500 ml. of anhydrous methylene chloride in a 1-1. three-necked flask equipped with a stirrer, gas-inlet tube, and drying tube (Note 1). The reaction flask is immersed in an ice bath, the stirrer is started, and 138 g. (3.00 moles) of dry dimethyl ether is passed into the solution from a tared cylinder over a period of about 2 hours. The reaction mixture is allowed to stand overnight at room temperature. An hour after the addition of dimethyl ether is complete, trimethyloxonium fluo-borate begins to separate. The initially liquid product solidifies slowly. 

TRIETHYLOXONIUM FLUOBORATE (Oxonium compounds, triethyloxonium tetrafluoroborate)... 

This compound was prepared according to T. J. Curphey, Org. 8yn., 51, 142 (1971). The submitters and the checkers stored and handled this material using the techniques outlined for triethyloxonium fluoborate in Note 1. 

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