Trialkyloxonium salts syntheses

The starting trialkyloxonium salts can be rather simply prepared from the corresponding dialkyl ethers. However, only trimethyl-and triethyloxonium boroflu-orides have been used in the synthesis of nitronates to prepare O-methyl and O-ethyl nitronates, respectively. 

Additional flexibility in the control over the selectivity of heterolytic reactions is provided in the diversity of electrophilic reagents that formally correspond to the same electrophile. For example, reagents such as RCO BF, RCOO-SO2CF3, RCOCl, and (RC0)20 are employed in synthesis as equivalents of the acyl cation RCO. However, a tremendous difference in the reactivity of these acylating species enables one to choose a reagent specifically adjusted to the peculiarity of the nucleophilic counterpart. In a similar way, such unlike compounds as trialkyloxonium salts, R30 BF7, alkyl halides, tosylates, or acetates can serve as transfer agents of the same alkyl cation, R, but they differ drastically in their activity and pattern of selectivity toward various nucleophiles. 

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