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M1
Received: 15 January 1997 / Published: 15 April 1997
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M3
Received: 15 January 1997 / Published: 15 April 1997
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M4
Received: 15 January 1997 / Published: 15 April 1997
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M5
Received: 1 February 1997 / Published: 15 April 1997
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M6
Received: 1 February 1997 / Published: 15 April 1997
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M7
Received: 1 February 1997 / Published: 15 April 1997
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M8
Received: 1 February 1997 / Published: 15 April 1997
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M9
Received: 1 February 1997 / Published: 15 April 1997
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M10
Received: 1 February 1997 / Published: 15 April 1997
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p. 62-68
Received: 25 October 1996 / Accepted: 17 January 1997 / Published: 10 April 1997
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| Download PDF Full-text (38 KB) Abstract: 2-Nitroaryldifurylmethanes 1a and 1b, readily available by condensation of 2-nitrobenzaldehyde and 6-nitroveratraldehyde with 2-methylfuran, were transformed into indole, cinnoline and benzothiazine-3,1 derivatives. The reduction of 2-nitroaryldifurylmethanes gave the corresponding anilines 2a,b or indole 3 depending on the reaction conditions. A plausible mechanism for the last reaction involving intramolecular heterocyclic addition between a nitroso-group and a furan ring is proposed. Diazotisation of the amine 2b gave a cinnoline derivative - a product of intramolecular oxidative furan ring opening. Treatment of isothiocyanates 7a,b with perchloric acid resulted in a new rearrangement with furan ring migration leading to the 4-H benzothiazine-3,1 derivatives.
p. 69-79
Received: 27 December 1996 / Accepted: 24 January 1997 / Published: 20 April 1997
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| Download PDF Full-text (48 KB) Abstract: Methyl 6H-furo[2,3-b ]pyrrole-5-carboxylate (2a) was prepared by thermolysis of the corresponding methyl 2-azido-3-(3-furyl)propenoate (1). 6-Methyl (2b) and 6-benzyl (2c) derivatives were obtained using phase-transfer catalysis conditions (PTC). The formylation of 2a-2c gave 2-formylated compounds (3a-3c). Compounds 4b, 4c were prepared by reactions of corresponding esters 2b, 2c with hydrazine in refluxing ethanol. By reaction of 3a-3c with hydroxylammonium chloride in acetic anhydride in the presence of pyridine, methyl 2-cyano-6-R1 -furo[2,3-b ]pyrrole-5-carboxylates (5a-5c) were obtained. The reaction of these compounds with sodium azide and ammonium chloride in dimethylformamide led to methyl 2-(5'-tetrazolyl)-6-R1 -furo[2,3-b ]pyrrole-5-carboxylates (6a-6c). A series of 5-methoxycarbonyl-6-R1 -furo[2,3-b ]pyrrole-2-carbaldehyde N,N -dimethylhydrazones (7a-7c) was prepared from methyl 2-formyl-6-R1 -furo[2,3-b ]pyrrole-5-carboxylates (3a-3c) and unsym-dimethylhydrazine. The correlation of the 13 C and 15 N chemical shifts with the data of the calculated (AM1) net atomic charges is discussed.
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