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Fused pyridine derivatives R 0450 Formation of the Pyridine Ring in the Synthesis of Dipyrido[3',2':4,5]thieno[3,2-b:3,2-d]pyridines. -Attempts to reduce the carbonyl group in ketones (I) with NaBH4 results in formation of the pentacyclic title heterocycle (II) instead of the expected alcohols. -(VASILIN, V. K.; LIPUNOV, M. M.; KONYUSHKIN, L. D.; KAIGORODOVA, E. A.; KRAPIVIN, G. D.; Chem. Heterocycl. Compd. (N. Y.) 42 (2006) 10, 1368-1369; Kuban State Technol. Univ., Krasnodar 350072, Russia; Eng.) -R. Langenstrassen 26-132

While continuing our investigations into the reactivity of substituted 3-aminothieno[2,3-b]pyridines [1, 2], we found a new reaction leading to closure of the pyridine ring during the formation of a pentacyclic heteroaromatic 22π-electronic system dipyridothienopyridine.During an attempt to reduce the carbonyl group of compounds 1a-d with sodium borohydride in ethanol the corresponding dipyrido[3',2':4,5]thieno[3,2-b:3,2-d]pyridines 3a-d were isolated from the reaction mixture instead of the expected amino alcohols 2. The mechanism of the transformations that occur is not quite clear and will be the subject of further investigations. N S Me NH 2 R O MeO NaBH 4 N S Me N S N Me R MeO OMe N S Me NH 2 R OH MeO 2 1a-d 3a-d 1, 3 a R = Ph; b R = C 6 H 4 Br-4; c R = C 6 H 3 Cl 2 -2,4; d R = MeThe 1 H NMR spectra were recorded in trifluoroacetic acid (compounds 3a-c) and DMSO-d 6 (compound 3d) on a Bruker DRX-500 instrument (500 MHz).Synthesis (General Procedure). Compound 1 (0.005 mol) was dissolved by heating in ethanol (20 ml), and sodium borohydride (7.5 mmol) was added while the reaction mixture was stirred. The obtained solution was boiled for 3 h, cooled, and neutralized with a 10% solution of hydrochloric acid. The flocculent precipitate was separated and washed with boiling DMF, water, and ethanol. The products were recrystallized from ethanol. __________________________________________________________________________________________

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Fused pyrimidine derivatives R 0515 Synthesis of Pentacyclic Systems Based on 3-Amino-2-(benzimidazolyl-2)thieno[2,3-b]pyridine. -(KAIGORODOVA, E. A.; VASILIN, V. K.; OSIPOVA, A. A.; LIPUNOV, M. M.; KRAPIVIN, G. D.; Izv.