For many years isatin has been the most studied derivative of indole. A multitude of dyes, pesticides, plant growth stimulators, analytical reagents, etc., have been made based on this compound. Isatin may be successfully used as the starting material for the synthesis of drugs with a wide range of physiological effects [1, 4].In a continuation of studies of the synthesis of tetracyclic condensed systems including a pyrrole ring we have developed a preparative method for the production of the isomeric 2,3-dioxo-2,3-dihydro-lH- -and 4-aminodibenzofurans [5, 6] were used as starting materials. Reaction of the amines with chloral hydrate and hydroxylamine hydrochl0ride in acid medium gave the corresponding isonitrosoacetamidodibenzofurans I and II, cyclization of which in sulfuric acid gave the desired systems III and IV.During a study of these heterocycles it was established that compounds III and IV can be successfully converted by reduction into the corresponding benzo[b]furoindoles V and VI, the yield depending on the choice of reducing agent. For example with lithium tetrahydroaluminate in anhydrous pyridine mixtures are formed which consist of the corresponding 3-hydroxybenzo[b]furoindoles VII and VIII (40 and 45 %), small amounts of the unsubstituted compounds V and VI (5 and 10%), and the unreacted starting materials III and IV. Use of diborane in tetrahydrofuran at -78~ gave the corresponding benzo[b]furoindoles V and VI in quantitative yields.The method we have developed permits to reduce the number of steps in the synthesis of heterocycles V and VI in comparison with the Fischer method [7], and, no less important, it permits the isolation and characterization during the reduction process of the corresponding hydroxy derivatives VII and VIII, which have not been reported previously, and which are of considerable interest from the pharmacological point of view [8].Georgian Technical University, Tbilisi 380075.
Fused pyrrole derivatives R 0160 Synthesis and Reductive Reactions of 2,3-Dioxo-2,3-dihydrobenzo[b]furo[2,3-f]-, -[2,3-g]-, and -[3,2-e]indoles. -The reduction of the title compounds (IV), (IX), and (X), prepared by Sandmeyer reaction from the corresponding derivatives (III) and (VIII), is studied. The reduction with in situ prepared diborane leads to the benzo[b]furoindoles [cf. compounds (V), (XI), and (XIII)], while the use of LiAlH4 in Py as reducing agent allows to synthesize three novel hydroxybenzo[b]furoindoles [cf. derivatives (VI), (XII), and (XIV)]. -(KHOSHTARIYA, T. E.; MATNADZE, M. M.; MIRZIASHVILI, N. T.; KURKOVSKAYA, L. N.; SIKHARULIDZE, M. I.; DZHASHI, T. O.; Chem. Heterocycl.
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