Tetrafluoroboric acid → 2,6-Bis(1,1-dimethylethyl)-4-methylselenopyrylium tetrafluoroborate

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Reaction Conditions

Reaction Steps

Methyl magnesium chloride (40 mL of a 3 M solution in tetrahydro-furan, 0.12 mole) was added to a solution of 2,6-bis[1,1-dimethylethyl]seleno-pyran-4-one (22 g, 0.081 mole, prepared in Part C above) in dry tetrahydrofuran (100 mL) which was initially maintained at −20° C. using a cold bath; the addition was effected at such a rate that the temperature in the reaction vessel did not exceed −15° C. The cold bath was removed, and the pale yellow solution was allowed to stir at room temperature for four hours, during which time a thick slurry formed. The mixture was then poured into ice/water (1 L) with rapid agitation, and tetrafluoro-boric acid (200 mL of a 48% aqueous solution) was added. Stirring was continued for a further two hours, after which the mixture was extracted with dichloromethane (3×100 mL). The organic layer was dried over magnesium sulfate and concentrated under reduced pressure to give a tan residue, which was triturated with ether. The resultant solid was collected by filtration, washed with ether and dried to give 2,6-bis(1,1-dimethylethyl)-4-methylselenopyrylium tetrafluoroborate (24.7 g, 85% yield) as an off-white solid melting at 65-66° C. The structure of this compound was confirmed by mass spectroscopy and by 1H and 13C NMR spectroscopy.

Provenance & Evidence