Synthesis of methyl 4H-furo[3,2-b]pyrrole-5-carboxylate is taken place in two step synthesis. Vilsmeier-Haack reaction of 4H-furo[3,2-b]pyrrole-5-carboxylate 1 led to methyl 2-formyl-4H-furo[3,2- b]pyrrole-5-carboxylate 4, which served as starting compound for synthesis of furo[3,2-b]pyrrole-2- aldoxime 5 and methyl 2-[(4-oxo-2-thioxo-1,3-thiazolidin-5-ylidene)methyl]-4H-furo[3,2-b]pyrrole-5- carboxylate 7. The hydrazinolysis of 1 was prepared by carbohydrazide 2, which subsequently reacted with aldehydes to form of derivatives 3. Pyrazole derivatives 11 were prepared by the reaction of azlactone 9 with derivatives 10. Reactions were carried out under microwave irradiation or at classical heating.
The 1H and 13C NMR spectroscopic properties of a series of furo[2′,3′:4,5]pyrrolo[1,2-d][1,2,4]triazin-8(7H)-ones and -thiones were investigated. The influence of various electron donating as well as electron withdrawing substituents at C-5 or N-7 on 1H NMR chemical shifts as well as 13C chemical shifts at C8 were observed. The 5-chloromethyl group had a little influence on the chemical shift of H-7 proton and the 8-thione group causes deshielding of H-7 as well as H-5 protons in comparison with the C-8 carbonyl group.
Ivana Zemanová, Michaela Potančoková and Renata Gašparová
6-Acetylbenzo[b]chromeno[2,3-e][1,4]diazepin-13(6H)-one 6 was synthesized by reaction of 4- oxo-4H-chromene-3-carboxaldehyde 1 with 1,2-diaminobenzene 2 followed by cyclisation of formed Schiff base 3 and spontaneous oxidation of dihydrodiazepine 4 by air oxygen. Finally, diazepine 5 was acetylated at N(6) by reaction with acetic anhydride.