Five-Membered Heterocycles with One Heteroatom

Synthesis of 2‐formyl‐1‐aza‐dibenzo[e,h]azulenes

“…Accordingly, the NOE contact between protons H(1) (7.41 ppm for both 5a and 5c) and H(12) (6.89 ppm for 5a or 6.78 ppm for 5c) confirmed that isomer with lower intensity of 1 H signals is Z isomer. Calculation of the integrated proton peak intensities involving H (12) and H(13) was used to determine the ratios between isomers. E vs. Z isomer ratio is estimated to be 80%:20% for oxa-(5a) and 85%:15% for thiaanalogue (5c).…”

Bazi İmi̇dazol Ve Ti̇yazol Bağli Asetami̇t Bi̇leşi̇kleri̇ni̇n Asi̇tli̇k Sabi̇tleri̇ni̇n İncelenmesi̇ Ve Değerlendi̇ri̇lmesi̇

“…According to the literature, the pK a values are 7.00 and 4.10 for the imidazole and 4-phenyl-2-aminothiazole, respectively [47][48]. As indicated in Table 2, the first acidity constant values of the acetamide derivatives are greater than 7.00.…”

1,2,4- and 1,3,4-Oxadiazoles as Scaffolds in the Development of Antiparasitic Agents

“…39 Considering the aromaticity of the 1,3,4-oxadiazole core as a 6π electron system, the two nitrogen atoms have each one electron pair fully available to receive a hydrogen bond. These interactions are observed in the binding site of raltegravir (9) in the HIV-1 integrase. The nitrogens are linked to the cation Mg 2+ by two water molecules, as shown in Figure 11a.…”

“…They were firstly discovered in 1884 by Tiemann and Krüger, 8 then named furo [ab]diazoles. Oxadiazoles can be isosterically compared with furan, 9 but the replacement of two methine groups (−CH=) by two sp 2 nitrogen (−N=) reduces their aromaticity so that some of their isomers are electronically comparable to conjugated diene systems. Oxadiazoles can be found in four different isomeric structures (Figure 4).…”