• V Venkateswarlu

      Articles written in Proceedings – Section A

    • The remarkable fluorescence of certain coumarin derivatives

      S Rangaswami T R Seshadri V Venkateswarlu

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      A number of umbelliferone derivatives with acetyl, benzoyl, carbethoxyl or carboxyl groups in the 3-position have been prepared of which 6 are new. The fluorescence exhibited by these has been studied and the results are discussed.

    • Synthetic experiments in the benzo-pyrone series - Part IV. Synthesis of karanjin

      T R Seshadri V Venkateswarlu

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      The methyl ether of karanjic acid has been converted into 5-ω-methox acetyl-4-methoxycoumarone which is found to be identical with the meth ether of the ketone obtained by the hydrolysis of karanjin with alka Following a similar procedure 5-ω-methoxyacetyl-4-hydroxycoumaroi has been synthesised from karanjic acid and this yields karanjin when col densed with benzoic anhydride and sodium benzoate. Thus all the stages the complete synthesis of karanjin have been accomplished.

    • Nuclear methylation of β-resorcylic aldehyde

      T R Seshadri V Venkateswarlu

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      A survey of past work on the nuclear methylation and ethylation of resorcinol and phloroglucinol derivatives is given and a mechanism for this reaction suggested. The nuclear methylation of β-resorcylic aldehyde has now been carried out giving rise to a good yield of the product (A). Its constitution as 4-methoxy-3-methyl-2-hydroxy benzaldehyde has been established in two ways: (i) A sample of 4-methoxy-3-methyl-2-hydroxy benzaldehyde was prepared according to the synthetic method of Jones and Robertson and compared with (A). (ii) The corresponding coumarin was prepared from (A) and was identified as 7-methoxy-8-methyl coumarin by comparison with the compound obtained by independent synthesis, starting from 2-methyl-resorcinol and passing through 7-hydroxy-8-methyl-coumarin as an intermediate stage. The same coumarin was also prepared by the reduction of umbelliferone-8-aldehyde and subsequent methylation.

    • The reactivity of the double bond in coumarins and related unsaturated carbonyl compounds - Part VIII. Addition of cyanoacetamide to umbelliferone and its methyl ether

      T R Seshadri V Venkateswarlu

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      The addition of cyanoacetamide to the double bond of 7-methoxy and 7-hydroxycoumarins is very slow and it is attributed to the influence of the substituents which act as electron sources. On hydrolysis, the products yield the corresponding cyanoacetic acid and acetic acid derivatives the latter of which could also be obtained by the reduction of methoxy and hydroxy coumarin-4-acetic acids using sodium amalgam. These compounds do not fluoresce in solution.

    • Visible fluorescence and chemical constitution of compounds of the benzopyrone group - Part III. Further study of structural influences in coumarins

      V Balaiah T R Seshadri V Venkateswarlu

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      From the data presented in the paper, the following points have been established: (1) Dihydro-umbelliferone and its derivatives, in which the pyrone double bond does not exist, do not give any fluorescence. (2) Similar to the carbonyl group cyano and phenyl groups enhance fluorescence emission markedly when present in the 3 position of umbelliferone. (3) No such effect is noticed when these groups occupy position 4. (4) A similar lack of influence is noticed in umbelliferone-3-acetic acid and its derivatives in which a methylene group breaks the conjugation. (5) Amongst monohydroxy coumarins, the presence of the hydroxy group in position 7 is most effective; in position 6, a feeble effect exists; in positions 5 and 8 no fluorescence is noticed. (6) Amongst dihydroxy-coumarins 6∶7, 5∶7, 8∶7, represent a decreasing series, the last giving no fluorescence. Derivatives of higher polyhydroxy-coumarins do not exhibit fluorescence. (7) Effect of methylation of the hydroxyl groups introduce marked changes in the capacity of the compounds to fluoresce and the colour of the fluorescence. 5-Methoxy-coumarin emits a feeble fluorescence whereas 8-methoxy compounds do not. (8) A few compounds exhibit fluorescence in the solid state. The above observations are explained from the effect of the structural features on the resonance of the molecule.

    • Synthetic experiments in the benzopyrone series - Part VII. Some stages in the synthesis of karanjin

      T R Seshadri V Venkateswarlu

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      The initial stages in the synthesis of karanjin have been reinvestigated. A new synthesis of karanjol starting form ψ-resorcylic aldehyde is described. The aldehyde is condensed with bromoacetic ester (1 mol.) in the presence of sodium alcoholate and the product hydrolysed and eventually converted into 4-hydroxy-coumarone by well-known stages. The preparation of karanjic acid from karanjol is male best through the action of sodium methoxide and carbon dioxide. Further stages leading to the synthesis of karanjin have already been described.

    • Fluorescence reactions with boric acid ando-hydroxy-carbonyl compounds, and their application in analytical chemistry - Part II. Detection of in Aromatic Compounds containing C, H and O only

      K Neelakantam L Ramachandra Row V Venkateswarlu

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      Addition of boric acid to aromatic compounds (C, H, and O only) of various types containing the, dissolved in concentrated sulphuric acid generally produces a marked intensification or a change in colour of the fluorescence exhibited by them in daylight or under the lamp In several cases the solution of the compound in sulphuric acid is itself non-fluorescent and fluorescence appears on adding boric acid

      In a few cases even when this group is present no fluorescence effects are obtained with boric acid.

      3∶7-Dihydroxy-flavone and its 7-methyl ether are exceptions in that they give positive reactions with boric acid even though the above group is absent.

      The fluorescence effects obtained with boric acid could be utilised for the detection of the in various types of aromatic compounds containing carbon, hydrogen and oxygen only. A positive reaction indicates the presence of this group but the converse is not true

      This reaction is more general than all the others described in literature and is also easily carried out.

      Further work is in progress.

    • Fluorescence reactions with boric acid andO-hydroxy-carbonyl compounds, and their application in analytical chemistry - Part III. Effect of bromination of theO-hydroxy-carbonyl molecule on the appearance of fluorescence effects with boric acid

      K Neelakantam V Venkateswarlu

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      The introduction of bromine atoms into the molecule of anO-hydroxycarbonyl compound does not invariably result in absence of fluorescence effects on the addition of boric acid.

      The fluorescence test for theO-hydroxy-carbonyl group is also applicable in the case of brominated compounds but as with the bromine-free compounds a negative result does not necessarily mean absence ofO-hydroxycarbonyl group. Negative results are obtained more often when bromine is present than in its absence.

    • Synthesis and study of 5 ∶ 6 ∶ 7 ∶ 8-hydroxy-flavonols

      T R Seshadri V Venkateswarlu

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    • Constitution of calycopterin

      T R Seshadri V Venkateswarlu

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      The constitution of calycopterin as 5 ∶ 4′-dihydroxy-3 ∶ 6 ∶ 7 ∶ 8-tetramethoxy-flavone has been confirmed. Calycopterin diethyl ether has been shown to have ethoxyl groups in the 5 and 4′-positions, since on fission with alcoholic alkali, it yieldsp-ethoxy benzoic acid and 2-hydroxy-ω ∶ 3 ∶ 4 ∶ 5-tetramethoxy-6-ethoxy acetophenone. The constitution of the ketone has been established by methylation and comparison with a synthetic sample obtained by the ethylation of ω ∶ 2 ∶ 3 ∶ 4 ∶ 5-pentamethoxy-6-hydroxy-acetophenone.

    • Constitution of cannabiscitrin—Part II

      T R Seshadri V Venkateswarlu

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      The methylation of the glucoside, cannabiscitrin and of the aglucone, cannabiscetin has now been effected by a more efficient method and the fission products examined. As the result cannabiscetin has been identified as myricetin and the identity has been confirmed by comparison of the flavonol and its derivatives with synthetic samples. It is noted that the reactions of flavonols having the pyrogallol side-phenyl nucleus exhibit many similarities with those given by flavonols having the 5∶7∶8-arrangement of hydroxyl groups. The condensation of hydroxy-fisetol-trimethyl ether with the anhydride and sodium salt of gallic acid yields pentamethyl-myricetin instead of the expected hexamethyl ether, partial demethylation having taken place in the 5 position during the course of the condendation.

      Methylation of the glucoside, cannabiscitrin yields a pentamethyl ether which forms on hydrolysis pentamethyl cannabiscetin (myricetin). Alkali fission of this compound gives the same ketone as the hexamethyl ether. The acid part is identified as 4∶5-dimethyl gallic acid, thus locating the position of the sugar group definitely in the 3′ position of the flavonol. This result has been confirmed by ethylating the pentamethyl cannabiscetin and subjecting the ethyl ether to fission with alkali. Besides the ketone already mentioned, the acid decomposition product is found to be 3-ethyl-4∶5-dimethyl gallic acid by comparison with a synthetic sample. The synthesis of the ethyl-dimethyl gallic acid is described.

    • 5∶6∶7∶8-hydroxy-flavonols - Part IV. A synthesis of calycopterin

      T R Seshadri V Venkateswarlu

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      By the condensation of 2-hydroxy-ω: 3∶4∶5∶6-pentamethoxy-acetophenone with the anhydride and potassium salt ofp-benzoyloxy-benzoic acid is obtained 4′-hydroxy-3∶5∶6∶7∶8-pentamethoxy-flavone which yields calycopterin by partial demethylation using hydrobromic acid.

    • A note on the nuclear methylation of lecanoric acid

      V Venkateswarlu

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    • Synthesis of 5-hydroxyflavonols

      T R Seshadri V Venkateswarlu

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      The synthesis of some flavonols with only one hydroxy group in the 5-position of the benzo-pyrone part has been effected starting from the monomethyl ether of 2-acetyl resorcinol and adopting the chalkone method of Kostanecki. The mono-methyl ether of 2-acetyl resorcinol is condensed with benzaldehyde, anisaldehyde and veratric aldehyde and the resulting chalkones converted into flavanones and flavonols. Thus 3∶5-dihydroxy-, 3∶5∶4′-trihydroxy-, and 3∶5∶3′∶4′-tetrahydroxy flavones, their methyl ethers and acetates have been prepared and their properties studied. These flavonols differ markedly from the isomeric compounds containing only one hydroxyl group in the 7-position of the benzopyrone part.

    • Some analogues of phthalein dyes from succinic and maleic acids

      N V Chalapathi Rao T R Seshadri V Venkateswarlu

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      Resorcinol condenses with succinic anhydride forming resorcinolsuccinein as the main product and tetrahydroxy-dibenzoyl-ethane as a very minor by-product. Orcinol also gives a good yield of orcinol-succinein. These could be used conveniently for the preparation of halogen and mercury substituted derivatives. Resorcinol gives only a poor yield of the malein, the major condensation product with maleic anhydride being the diketone, tetrahydroxy-dibenzoyl-ethylene. Phenol does not give any isolable quantity of succinein or malein and only the corresponding diketones could be isolated by condensation with succinic anhydride and maleic anhydride. A number of derivatives of the diketones are described.

    • Nuclear oxidation in flavones and related compounds - Part XXXI. Synthesis of 3-hydroxy primetin and its nuclear oxidation

      T R Seshadri S Varadarajan V Venkateswarlu

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      3-Hydroxy primetin has been synthesised starting with 3∶5-dihydroxy flavone and using partial methylation, para nuclear oxidation and final demethylation. During the last stage no isomeric change is noticed. This is in conformity with the behaviour of similar cases of flavonol derivatives and is different from the behaviour of analogous flavone derivatives. Orthooxidation of 3-hydroxy primetin leading to the synthesis of the lowest member of the gardenin series is found to proceed satisfactorily.

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