Triphenylbismuthonium 2-oxoalkylide, a moderately stabilized bismuthonium ylide: generation and reactions with some electrophiles

Abstract

Treatment of (2-oxoalkyl)triphenylbismuthonium tetrafluoroborates 3 with potassium tert-butoxide in tetrahydrofuran at –78 °C produced triphenylbismuthonium 2-oxoalkylides 4, which readily underwent epoxidation with the aldehydes 5 to give the α,β-epoxy ketones 7 with high traps selectivity. The ylide 4a reacted with dimedone 11, the sulfonic acid 13, the thiol 15 and the isocyanate 17 to afford the corresponding ketones 12, 14, 16 and 19 in moderate to good yields. Reaction of the ylide 4c with the α,β-unsaturated ketones 10 and 21 afforded the 1,2-dibenzoyl- and the 1,2,3-tribenzoyl-cyclopropanes 20 and 22, respectively, although the yields were low. In the presence of a catalytic amount of nitrosobenzene 23, the ylide 4a suffered a unique decomposition to give the 2,2,7,7-tetramethyloct-4-ene-3,6-dione 24 in quantitative yield, while the reaction with the nitrite oxide 25 yielded the isoxazoline 26. In all of these reactions, triphenylbismuthane 6 was the additional major product.