[CH3:1][Mg]Cl.[CH3:4][C:5]([C:8]1[Se:9][C:10]([C:15]([CH3:18])([CH3:17])[CH3:16])=[CH:11][C:12](=O)[CH:13]=1)([CH3:7])[CH3:6].[F:19][B-:20]([F:23])([F:22])[F:21].[H+]>O1CCCC1>[F:19][B-:20]([F:23])([F:22])[F:21].[CH3:4][C:5]([C:8]1[CH:13]=[C:12]([CH3:1])[CH:11]=[C:10]([C:15]([CH3:18])([CH3:17])[CH3:16])[Se+:9]=1)([CH3:7])[CH3:6]Methyl magnesium chloride (40 mL of a 3 M solution in tetrahydrofuran, 0.12 mol) was added to a solution of 2,6-bis[1,1-dimethylethyl]selenopyran-4-one (22 g, 0.081 mol, 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 tetrafluoroboric 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 solid which resulted 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 which melted at 65°-66° C. The structure of this compound was confirmed by mass spectroscopy and by 1H and 13C NMR spectroscopy.
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