The electrochemistry of 2,2-dimethyl-(3H)-3-(N-3'-nitrophenylamino)naphtho[1,2- b]furan-4,5-dione ([Q]-PhNO2), on mercury was investigated. The first peak is consistent with a quasi-reversible one-electron reduction of the ortho-quinone, forming [Q•-]-PhNO2, while the second one, bielectronic, corresponds to the simultaneous reduction of the latter radical to a dianion and the nitro group to a nitro radical anion. The second order rate constant, k disp, for the decay of [Q•-]-PhNO2 is 15.188 x 10³ ± 827 mol"1 L s"1 and the t1/2 equals 0.06 s. E¹7Ic values for [Q]-PhNO2 and its precursor, nor-β-lapachone, are similar. The ease of semiquinone generation and its stability are parameters statistically relevant in the correlation biochemical/theoretical aspects.

Os cromenos, dihidropiridinas e piridinas substituídos têm-se revelado importantes na síntese de compostos com propriedades farmacológicas interessantes. Consequentemente, achamos importante a síntese de cromenopiridinas e cromenodihidropiridinas (ou seja, anéis fundidos do cromeno e da dihidropiridina ou da piridina) de forma a pesquisar a sua atividade biológica. Neste estudo, propomos a síntese "one-pot " para 2,4-dimetil-5-oxo-5H-cromeno[4,3-b]piridina-3-carboxilatos de etilo, 2,4-dimetil-5-oxo-5H-cromeno[3,4-c]piridina-3-carboxilatos de etilo substituídos e as suas respectivas 1,4 dihidropiridinas, baseada numa síntese modificada da piridina de Hantzsch usando 2-hidroxiaril aldeído, com os grupos que retiram e doam elétrons no anel fenil, como reagentes iniciais. Dezesseis compostos foram sintetizados pelo método descrito e completamente caracterizados. Um rendimento médio de 37% foi obtido para os diferentes derivados.

Substituted chromenos, dihydropyridines and pyridines have been important in the syntheses of compounds having interesting pharmacological properties. Therefore, we found of interest to synthesize chromenopyridines and chromenodihydropyridines (i.e., fused chromeno and dihydropyridine or pyridine rings) to further study their biological activity. Here, we propose one-pot syntheses for substituted ethyl-2,4-dimethyl-5-oxo-5H-chromeno[4,3-b]pyridine-3-carboxylates, ethyl-2,4-dimethyl-5-oxo-5H-chromeno[3,4-c]pyridine-3-carboxylates and their respective 1,4-dihydropyridines based on a modified Hantzsch pyridine synthesis using 2-hydroxyaryl aldehydes, with electron withdrawing and electron donating groups on the phenyl ring, as starting reactants. Sixteen compounds were synthesized by the described method and fully characterized. An average yield of 37% was obtained for the different derivatives.

Derivados de 1,4-dihidropiridina constituem um importante grupo farmacológico para o tratamento de doenças cardiovasculares. Sintetizamos neste trabalho uma série de 4-(5'-nitro-2'-furil)-1,4-dihidropiridina derivados, os quais foram caracterizados por ¹H RMN. Observamos que grupos carboxílicos em C-3 e C-5 no anel 1,4-dihidropiridine mostram um sinal muito mais complexo no espectro de ¹H RMN, tanto quando C-4 é um centro quiral ou pseudo-quiral.

1,4-dihydropyridine derivatives constitute an important pharmacological group for the treatment of cardiovascular diseases. We have synthesised a series 4-(5'-nitro-2'-furyl)-1,4-dihydropyridine derivatives, which were characterised by ¹H-NMR. We have found that carboethoxy groups at the C-3 and C-5 on the 1,4-dihydropyridine ring show a much more complex signal in the ¹H NMR spectra, either when C-4 is a pseudo-prochiral or a chiral centre.