Triethyloxonium borofluorides

The action of methyl iodide on chloro-substituted heterocychcs usually results, in addition to quatemization, in the replacement of the chlorine by iodine if the halogen is in a position alpha or gamma to the quaternary center, particularly so in the former case. This type of replacement is less likely if dimethyl sulfate is used but may still occur to give a sulfate betaine (see Section IV, C). An easy method to obtain a-halogeno-quatemary salts has recently been discovered by Balli and Kersting who reacted the readily accessible triethyloxonium borofluoride 12 with a variety of bases. The very... 

The formation of quaternary salts by attack at an oxygen atom is only achievable in certain special cases. Most of the attempts to effect reactions of this type with N-alkyl-a-oxo derivatives have failed. Until recently it might have been assumed that 2-alkoxy-quaternary salts were unobtainable, the usual product from reactions with the alkoxy derivatives being the N-alkyl-oxo compounds (see Section IV,C). Recently, however, Meerwein and his co-workers found that triethyloxonium borofluoride and a number of N-methyl-a-oxo... 

Treatment of 83 with an electrophile such as methyl sulfate, allyl bromide, or triethyloxonium borofluoride, followed by oxidation of the resulting vinylic borane... 

A full account has appeared of the alkylation of the ester phosphorane Ph8p= CHC02Et with triethyloxonium borofluoride and of the reactions of the resulting ylide Ph3P=C=C(OEt)2- The cumulated phosphoranes (36) and... 

Chemical evidence is never unequivocal in indicating the position of a tautomeric equilibrium. For a number of both a- and jS-hydroxypyrroles, physical data are available. Thus, comparison of the ultra-violet spectra of the compounds (96) with those of their necessarily pyrrolic O-acetyl esters (97) proves clearly the predominance of the oxopyrroline forms in ethanol H. In contrast, the chemical evidence is confused the compounds are soluble in alkali, give no ferric reaction, give benzylidene derivatives, do not react with diazomethane and undergo both O- and C-acetylation. The formulation of 2-hydroxy-3,4-dimethylpyrrole as 3,4-dimethyl-2-oxo-J -pyn-oline (98) is supported by proton resonance data ss. In contrast, the formyl group appears to stabilize the hydroxy form (99) 55. O-Ethylation of (98) is conveniently effected by triethyloxonium borofluoride se. 

Preparation. One mole of triethyloxonium fluoroborate (I) is covered with dimethylformamide in a flask cooled in salt-ice, and the mixture is stirred vigorously under reflux. A vigorous reaction is soon over, and dimethylaminoethoxycarbonium fluoroborate (2) separates as a lower layer. This is separated and added dropwise to a solution of sodium ethoxide in ethanol. The sodium borofluoride which separates is removed, and the acetal (3) is separated by fractionation. 

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