N M Shah
Articles written in Proceedings – Section A
Volume 13 Issue 5 May 1941 pp 352-358
The condensation of acetoacetic ester with substituted resacetophenones in the presence of aluminium chloride has been investigated. 5-Ethyl-resacetophenone, 5-bromo-resacetophenone underwent the condensation giving the expected 5-hydroxy-6-acetyl-coumarin derivatives. 4-Acetyl-α-naphthol and 4-propionyl-α- naphthol underwent the condensation but the product obtained was found to be 4-methyl-1: 2-α-naphtha-pyrone, the acyl group being split off during the condensation. Negative results were obtained with 5-nitro-resacetophenone, 5-benzyl-resacetophenone, ω-methoxy-resacetophenone, methyl-β-resacetophenone carboxylate, 4:6-diacetyl-resorcinol and 2:4-diacetyl-resorcinol. The results obtained have been explained; negative groups like-NO2,-CO.Me, etc., hinder the reaction, while positive groups like-C2H5 have no de-activating effect on the course of the reaction.
Volume 14 Issue 2 August 1941 pp 151-157
The reduction of −CH(OH)CCl3 group attached to a benzo-α-pyrone nucleus has been studied for the first time, the reducing agents used being zinc dust and glacial acetic acid either in conjunction with conc. HCl or without it. It is found that the course of the reduction is highly affected by the constitutional factors. The following generalisation is made in this connection:
Volume 16 Issue 6 December 1942 pp 387-391
The action of benzoyl chloride on 5-hydroxy-6-acyl-coumarins in pyridine solution has been investigated. The reaction leads to the formation of the flavone derivative instead of the expected benzoyloxy derivative. The constitution of the flavone obtained from 5-hydroxy-6-acetyl-coumarin has been confirmed by unambiguous synthesis from the corresponding chalkone by SeO2 reaction. 5-Hydroxy-6-propionyl-coumarin similarly gives the flavone derivative and also reacts in its enolic form, yielding the di-benzoyloxy derivative. 5-Hydroxy-6-butyryl-coumarin gives only the di-benzoyloxy derivative, reacting in its enolic form.
Volume 17 Issue 1 January 1943 pp 7-10
The condensation of resacetophenone with several α-substituted acetoacetates with anhydrous aluminium chloride as condensing agent has been investigated. Ethyl α-methyl-, α-ethyl-, α-benzyl-acetoacetates undergo the condensation with the formation of 5-hydroxy-6-acetyl-3-alkyl-coumarin derivatives. Negative results were obtained with ethyl α-prophyl-, α-allyl, α-chloro-acetoacetates, the original ketone being recovered. The results obtained have been discussed.
Volume 32 Issue 6 December 1950 pp 386-389
The synthesis of 6-hydroxy-flavonols has been effected by the Algar and Flynn oxidation of 2∶5-dihydroxy-, 2∶5∶2′-trihydroxy-, 2∶5∶4′-trihydroxy-chalkones and 6∶3′-dihydroxy- and 6∶4′-dimethoxy-flavanones by means of alkaline hydrogen peroxide. The flavonols obtained have been characterised by preparing their acetyl or methoxy derivatives. It is interesting to note that free hydroxyl group in either nucleus of the chalkone molecule does not lead to complications during the oxidation, the flavonols being obtained in good yield.
Volume 33 Issue 2 February 1951 pp 112-115
6-Hydroxy-flavones have been synthesised by the Venkataraman oxidation of 2:5-dihydroxy-, 2:5:2′-trihydroxy-, 2:5:4′-trihydroxy chalkones as well as 6:3′-dihydroxy-flavanone by selenium dioxide. Thus the polyhydroxy-chalkones can be oxidised to the corresponding hydroxy-flavones in one step.