The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Synthesis of iodo derivatives of the furan series. 5-Iodofurfural》. Authors are Nazarova, Z. N..The article about the compound:5-Iodo-2-furaldehydecas:2689-65-8,SMILESS:IC1=CC=C(O1)C=O).Synthetic Route of C5H3IO2. Through the article, more information about this compound (cas:2689-65-8) is conveyed.
All 5-bromo or -iodo derivatives of furan lose halogen quant. on standing 48 h. in the dark in HNO3 (d. 1.4) in the presence of AgNO3, followed by heating to 50-60° until N oxide vapor appear; the method can be used for anal. of these compounds Refluxing 35 g. 5-bromofurfural with 3.5 g. KI and 180 mL. AcOH 1 h., followed by dilution with H2O gave 96% crude product, m. 124-6°, which gave 80% pure 5-iodofurfural, m. 127.5-8° (from EtOH); with HNO3 it gives vapor of iodine; oxime, decompose 167-8°; semicarbazone, decompose 199-200°. The aldehyde in 30% NaOH treated with a few drops H2O2 and kept 4 days, then acidified, gave 58.8% 5-iodofurancarboxylic acid, decompose 197-8° (from H2O). The aldehyde heated with Ac2O-AcOK at 145-50°, then boiled with a little H2O 15 min. gave 82.2% 5-iodo-2-furylacrylic acid, decompose 159-60° (from dilute dioxane). The aldehyde condensed with MeNO2 (cf. C.A. 49, 9606b) gave 86% 1-(5-iodo-2-furyl)-2-nitroethylene (I), yellow-orange, m. 112-13° (from EtOH); if the intermediately formed Na salt is filtered directly from the mixture and is carefully decomposed with AcOH after washing with Et2O and MeOH, there is formed the unstable nitro alc., orange-red oil, which after steam distillation gave 80% I, m. 112-13°. The Br analog heated with KI and NaI in AcOH 2 h. on a steam bath gave 82.6% I. Heating 2-(5-bromo-2-furyl)-1-chloro-1-nitroethylene (cf. loc. cit.) with NaI in AcOH 2 h. gave 48.2% 5-iode analog, C6H3BrCINO3, m. 109-9.5° (from EtOH), an irritant which loses iodine on heating with HNO3.
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Reference:
1,8-Naphthyridine – Wikipedia,
1,8-Naphthyridine | C8H6N2 – PubChem