TRIPHENYLBISMUTHONIUM 2-OXOALKYLIDE, A MODERATELY STABILIZED BISMUTHONIUM YLIDE - GENERATION AND REACTIONS WITH SOME ELECTROPHILES

Treatment of (2-oxoalkyl)triphenylbismuthonium tetrafluoroborates 3 wi th potassium tert-butoxide in tetrahydrofuran at -78 degrees C produce d triphenylbismuthonium 2-oxoalkylides 4, which readily underwent epox idation with the aldehydes 5 to give the alpha,beta-epoxy ketones 7 wi th high trans selectivity. The ylide 4a reacted with dimedone 11, the sulfonic acid 13, the thiol 15 and the isocyanate 17 to afford the cor responding ketones 12, 14, 16 and 19 in moderate to good yields. React ion of the ylide 4c with the alpha,beta-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 o f a catalytic amount of-nitrosobenzene 23, the ylide 4a suffered a uni que decomposition to give the 2,2,7,7-tetramethyloct-4-ene,3,6-dione 2 4 in quantitative yield, while the reaction with the nitrile oxide 25 yielded the isoxazoline 26. In all of these reactions, triphenylbismut hane 6 was the additional major product.