Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Electrochemical methoxylation of 2-phenylfuran (I) and 2-(4-nitrophenyl)furan (VI) proceeded anomalously, affording 5-methoxy-2-phenylfuran (XI) and 5-methoxy-2-(4-nitrophenyl)furan (XIII), respectively. 2-Phenyl-5-methylfuran (II) and methyl-2-(2-methylphenyl)-3-furoate (VIII) behaved normally giving the respective 2,5-dimethoxy-2,5-dihydrofuran derivatives XII and XIV. The suggested EC_NEC_B mechanism of the anomalous methoxylation was confirmed by methoxylation of compound II, in which the methyl group hinders the last C_B step, and also of compound VIII in which the automaticity is suppressed by forced deviation from planarity. Forced deviation from planarity was moreover studied also on 2-(4-methylphenyl)furan (III), 5-methyl-2-(2-methylphenyl)furan (IV) and 3,5-dimethyl-2-(2-methylphenyl)furan (V) as model compounds. For all the derivatives the INDO charges were calculated and correlated with the ¹H- and ¹³C-NMR spectra. The experimental electronic spectra were correlated with the theoretical ones (INDO-S-CI). All the results obtained confirm the suggested mechanism.