33038-29-8

The total synthesis of oxacalothrixins, an isostere of biologically important carbazoloquinone alkaloid, calothrixin B was achieved from 2-acetyl-3-methylbenzofuran. An iodine/TBHP-mediated oxidative cyclization of benzofuranyl-enamine has been employed as a key step to synthesize, the crucial intermediate 1-hydroxy dibenzofurancarbaldehyde. The latter upon reductive cyclization followed by PIDA-mediated oxidation furnished oxacalothrixin B and its analogues.

New heterocyclic fulgides, 3-[1-(5-alkoxy-2-methylbenzo[b]furan-3-yl)ethylidene]-4-(2-propylidene)dihydro-2,5-furandiones, and fulgimides, 1-(2-dimethylaminoethyl)-3-[(5-methoxy-2-methylbenzo[b]furan-3-yl)ethylidene]-4-(2-propylidene)dihydro-2,5-pyrroledi

A series of heterocyclic quinones based on benzofuran, benzothiophene, indazole and benzisoxazole has been synthesized, and evaluated for their ability to function as substrates for recombinant human NAD(P)H:quinone oxidoreductase (NQO1), a two-electron reductase upregulated in tumor cells. Overall, the quinones are excellent substrates for NQO1, approaching the reduction rates observed for menadione.

The syntheses of a bicyclic furylfulgide 14 and a (benzofuryl)fulgide 15 with increased steric constraints are described. Their photochromic behaviors were analyzed by means of UV/Vis spectroscopic measurements, X-ray crystallography, and NMR experiments, and the results were compared to those of the furyl(methyl)fulgide 12 and the furyl(isopropyl)fulgide 13. Compounds 13E and 14E exhibit large quantum yields of 0.57 and 0.53 for the coloration reaction (E) → (C) compared with 12E and 15E (0.23 and 0.17). After irradiation with 350 nm light, 13E and 14E are transformed into the closed (C) forms almost quantitatively, whereas 12E and 15E result in a photostationary state with mixtures of the (E), (Z), and (C) forms. The crystal structures obtained for 13E, 14E, and 15E show that the fulgides adopt cyclizable helical (P)-Eα conformations with no significant differences in atomic distances in the hexatriene unit. 2D- and temperature-dependent NMR experiments showed that the enantio- and diastereotopomerization processes were suppressed in a fulgide for the first time. Compound 14E populates only the E α conformational state. In contrast, 13E and 15E both exist in the cyclizable Eα and the non-cyclizable Eβ conformations in solution. Due to the annulated benzene ring, 15E exhibits a higher thermodynamic barrier than 13E, so the "belly roll" process was reduced for 15, but the (E) → (Z) isomerization could not be suppressed. The structural modification of 14 successfully suppressed the (E) → (Z) isomerization as well as the belly roll process. The way in which the isomerization reaction is suppressed by steric hindrance could not be fully elucidated by using these methods. Copyright

Various fulgides based on benzofuryl and indolyl core units with versatile functionalities were synthesized. Substitution at the phenylic site shows only small effects on the photochromic properties compared to the parent compounds 30 and 31. Fulgide-dye

The benzofurans and naphthofurans so far were obtained either by using catalyst or as side products. In the present investigation we are reporting first time the exclusive formation of only 3-acetyl-5-hydroxy-2-methylbenzofuran and 3-acetyl-5-hydroxy-2-methyl-naphthofuran in quantitative yield by adopting the Nenitzescu reaction. Further, these 5-hydroxybenzofuran and 5-hydroxy-naphthofuran were converted to their corresponding 5-methoxyl/ 5-methoxycarbonylmethoxy derivatives.