Dimethyldioxirane Oxidation of 3-Arylidenechromanones

摘要: Oxidation of the (E) and (Z) isomers 3-arylidenechromanones 5 by isolated dimethyldioxirane (as acetone solution) at ambient temperature resulted in formation spiro epoxides trans- cis-6, respectively, moderate yields (23–51%), together with considerable amounts (16–40%) 3-aroylchromones 7 from both (E)- (Z)-5 isomers. Minor products, namely 3-(α-hydroxy-4-methoxy-benzyl)-4H-1-benzopyran-4-one (8b), 1a,7a-dihydro-7a-(α-hydroxy-4-methylbenzyl)-7H-oxireno[b][1]benzopyran-7-one (9d), 1a,7a-dihydro-7a-aroyl-7H-oxireno[b][1]-benzopyran-4-ones 10a–c have also been characterized. Presumably, can be attributed to competitive allylic oxidation afford first 3-(α-hydroxyarylmethyl)-chromones 8, whose secondary alcohol functionality is subsequently oxidized give 7. Further latter dioxirane affords 10, as established a control experiment. Alternatively, 8 yield epoxide 9 subsequent overoxidized product 10 cannot disposed on grounds our data. Nonetheless, despite desirable chromanone 6, stereoselective directly chromanones offers convenient preparation. Relative configuration stereochemistry compounds 6–10 were elucidated NMR spectroscopy AM1 calculations.