• V Ramanathan

      Articles written in Proceedings – Section A

    • Synthetical experiments in the chromone group - Part XXIX. A method for the reduction of 5:7-dihydroxyflavones to 5-hydroxyflavones

      V Ramanathan K Venkataraman

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      A general method for the preparation of 5-hydroxyflavone and its derivatives from the corresponding 5:7-dihydroxyflavones by the action of Raney nickel on the 7-tosyloxy derivatives is described. Thus chrysin has been converted into 5-hydroxyflavone, and galangin 3-methyl ether to 5-hydroxy-3-methoxyflavone.

    • Raney nickel reductions - Part III. Reduction of anthraquinone and its derivatives

      V Ramanathan B D Tilak K Venkataraman

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      Reduction of anthraquinone, 2-methylanthraquinone, 2-mercaptomethylanthraquinone (I),bis-2-anthraquinonylmethyl sulphide (II) andbis-2-anthraquinonylmethyl disulphide (III) by Raney alloy in aqueous alkaline solution was studied. Anthraquinone gave 1:2:3:4-tetrahydroanthraquinone. When 2-methylanthraquinone was reduced with varying amounts of Raney alloy, several hydro derivatives of 2-methylanthraquinone were obtained. One was 1:2:3:4-tetrahydro-6-methylanthraquinone, the constitution of which was proved by oxidation to adipic and 4-methylphthalic acids. Desulphurization of (I) gave 2-methylanthraquinone, 2-hydroxymethylanthraquinone and anthraquinone-2-carboxylic acid; (II) gave 2-methylanthraquinone and traces of Anthraflavone; and (III) gave 2-methylanthraquinone, 2-hydroxymethylanthraquinone and anthraquinone-2-carboxylic acid. Anthraflavone gave decahydroanthraflavone as the major product and a small amount of 1:2:3:4-tetrahydro-6-methylanthraquinone.

      Dehydrogenation of tetrahydro- and tetrahydromethylanthraquinones to the parent compounds was effected by several methods including treatment with iodine and sodium acetate in nitrobenzene and the action of activated alumina on a hexane solution. Treatment of tetrahydroanthraquinone with selenium dioxide at 170° gave a mixture of anthraquinone, α-hydroxyanthraquinone and quinizarin. Decahydroanthraflavone was dehydrogenated in two steps to Anthraflavone.

    • Synthetical experiments in the chromone group - Part XXX. A synthesis of 3:5:8:3′:4′-pentahydroxyflavone and its non-identity with ponderosin

      V Ramanathan K Venkataraman

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      By Raney nickel hydrogenolysis of the 7-tosyl ester (V), 5:7-dihydroxy-3: 3′:4′-trimethoxyflavone (IV) has been converted into 5-hydroxy-3:3′:4′-trimethoxyflavone (VI). Persulphate oxidation of (VI) gave 5: 8-dihydroxy-3: 3′:4′-trimethoxyflavone (VII), which was demethylated to 3:5:8:3′:4′-pentahydroxyflavone (III) by means of aluminium bromide in benzene. This pentahydroxyflavone was different in its properties from ponderosin, the yellow colouring matter ofPonderosa pine bark.

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