An efficient synthetic method of medicinally important chalcone‐derived heteroaromatics was proposed, which comprised of conjugate addition of ethyl acetoacetate to chalcones, followed by MnIII/CoII‐catalyzed oxidative deacetylation. Paal‐Knorr reactions of the resulting 1,4‐dicarbonyl compounds containing various phenyl substituents produced the corresponding 2‐carboethoxy‐3,5‐diphenyl furans, pyrroles, and thiophenes. The scope, mechanism, and electronic requirements for the phenyl substituents of chalcones in the key radical‐medicated deacetylation reaction were fully elucidated. Antibacterial activities of the 21 chalcone‐derived heteroaromatics were screened for Escherichia coli, Staphylococcus aureus, and Acinetobacter baumannii. The parent pyrrole 5 a showed most effective inhibition for E. coli and one third of the heteroaromatics exhibited significant inhibition for S. aureus at the concentration of 64 μg/mL.
Efficient synthetic method for medicinally and opto-electronically important bichalcophenes is reported, which highlights Mn(OAc)3/CoCl2-catalyzed oxidative deacetylation of 1,5-dicarbonyl compounds that were easily prepared by conjugate addition of ethyl acetoacetate to α,β-unsaturated carbonyl compounds containing a chalcophene unit. Paal–Knorr reaction of the resulting 1,4-dicarbonyl compounds produced 4-phenyl-2,2′-bichalcophenes and their aza-analogues.
The synthetic method of tetraphenyl‐substituted all‐E‐carotenes 1 with improved properties of antioxidant and molecular electronic conductance was developed through the formation of tetraphenyl‐substituted all‐E‐apocarotenedial 4. The synthesis highlighted the preparation of novel subunits containing phenyl substituent(s) with E‐configuration starting from the key (E)‐4‐chloro‐2‐phenylbut‐2‐enal (10), utilizing conjugation effect with formyl group or easy recrystallization of sulfone compounds. Sulfone‐mediated coupling methods of Julia and modified Julia–Kocienski olefinations utilizing the subunits were demonstrated to produce tetraphenyl‐substituted apocarotenedials 4. The major all‐E‐forms (73–85 % selectivity) were easily purified by SiO2 chromatography and trituration with Et2O due to the presence of the polar formyl groups. The olefination of all‐E‐apocarotenedials 4 and Wittig salt 5 provided all‐E‐9,9',13,13'‐tetraphenylcarotenes 1.
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