• A Kumar

      Articles written in Journal of Chemical Sciences

    • Synthetic studies in cinnamylated derivatives of resacetophenone and related compounds

      A C Jain A Kumar R C Gupta

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      Resacetophenone (1) reacts with cinnamyl bromide in the presence of K2CO3 and acetone to give its 4-O-cinnamyl derivative (2); whereas the same reaction in the presence of methanolic methoxide affords 3-C-cinnamyl-(6), 5-C-cinnamyl-(8) and 3,5-di-C-C-cinnamyl- (4) derivatives in the ratio of 36∶1∶15. Reaction of 1 with cinnamyl alcohol in boiling formic acid results in the formation of 8 in the largest amount followed by 6 and a new compound which is a mono-C-cinnamyl flavan (10 or 11). 6 was converted into the corresponding flavan (12), flavene (13) and 4-hydroxycoumarin (14).

      On Claisen rearrangement yielded a mixture of three compounds, two of which were found to be the normal products viz. 3-(1-phenyl-allyl) resacetophenone (18) and its 5-isomer (19). The third but major compound was the further rearranged but uncyclised 3-(1-phenyl-1-propenyl) derivative (15) which forms the corresponding chalcone (21) when condensed with anisaldehyde in the presence of alkali.

    • A convenient synthesis of lonchocarpin and isolonchocarpin

      A C Jain R C Gupta A Kumar

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      1, 1-Dimethyl propargylation of 7-hydroxyflavanone (5) with 2-chloro-2-methyl-3-butyne in the presence of K2CO3, Me2CO, KI and DMF yielded a mixture of four compounds. Its 1, 1-dimethyl propargyl ether (6) and the corresponding chalcone (7) resulted in major amounts; their corresponding cyclised products (2 and 1) also formed albeit in smaller amounts. These cyclised products, lonchocarpin (1) and isolonchocarpin (2) were the sole products when the above mixture was heatedN, N-dimethylaniline. Lonchocarpin (1) is best synthesized by 1,1-dimethyl propargylation of 2′ 4′-dihydroxychalcone (8) followed by heating inN, N-dimethylaniline, because it was noted that in the above two reactions, the flavanone ring tends to open out whereas the chalcone does not cyclise.

    • The Claisen rearrangement of 7-cinnamyloxy derivatives of 3-methoxyflavone, 4-methylcoumarin and isoflavone

      A C Jain D K Tuli A Kumar

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      The Claisen rearrangement of 7-cinnamyloxy derivatives of 3-methoxyflavone (2), 4-methylcoumarin (7) and isoflavone (13) yield 8-(1-phenyl-2-propenyl)-7-hydroxy-3-methoxyflavone (3), 4-methyl-8-(1-phenyl-1-propenyl)-7-hydroxycoumarin (9) and 8-(1-phenyl-1-propenyl)-7-hydroxyisoflavone (14) respectively. The compound 3 represents the normal rearranged product and further has structural features similar to those present in some natural neoflavonoids; whereas other products (9 and 14) are abnormal ones formed by further allylic rearrangement of the normal ones (say 8).

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