The action of mercuric acetate in methyl alcoholic solution on (1) umbelliferone, (2) 4-methylumbelliferone and (3) 4: 7-dimethylcoumarin has been investigated. With umbelliferone addition at the double bond and substitution in positions 6 and 8 take place whereas in the case of its 4-methyl derivative position 8 alone is mercurated to yield a monoacetoxymercuri-compound. In regard to the last compound the reaction stops with addition at the double bond and mercuration of the 6th position, the position 8 escaping the attack of the reagent. It is concluded that owing to the influence of the substitutent groups the reactivity of the three active centres of the coumarin molecule are differently affected.

The acetyl derivatives of coumaric, 4-methylcoumaric, 5-nitrocoumaric, psoralic and isopsoralic acids have been prepared and their behaviour studied under conditions which bring abouttrans tocis inversion. Under the influence of sunlight, the first three acids produce the corresponding coumarins on prolonged exposure. When heated to above their respective melting points all the acetyl compounds undergo inversion to an extent of 60–80%. Along with the pyrones, highly polymerised resinous compounds are also produced on heating. Treatment with equimolecular amounts of mercuric chloride in aqueous or aqueous alcoholic medium brings about inversion in all the cases with almost theoretical yields.

6∶7∶8-Trihydroxy and 6∶7∶8∶4′-tetrahydroxyflavones and their derivatives (methyl ethers and acetates) have been prepared starting with 2-hydroxy-3∶4∶5-trimethoxyacetophenone and adopting the Baker-Venkataraman procedure. Their properties and reactions have been studied and compared with those of the isomeric compounds, baicalein and scutellarein.

A simple and at the same time unambiguous method of synthesis of the 5∶6∶7-hydroxyflavones, baicalein and scutellarein and their derivatives is described. It starts from phloracetophenone which is partially methylated to the 4∶6-dimethyl ether. Oxidation of this ether with potassium persulphate yields the 2∶5-dihydroxy compound which on partial methylation produces 2-hydroxy-4∶5∶6-trimethoxyacetophenone. Using the benzoyl and anisoyl derivatives of this ketone and adopting the Baker-Venkataraman procedure, the trimethyl ether of baicalein and the tetramethyl ether of scutellarein have been prepared and from them the hydroxyflavones and their acetates.

Employing 2∶5-dihydroxy-4∶6-dimethoxyacetophenone and the Allan-Robinson method, the 5∶7-dimethyl ether of baicalein is obtained and from it by partial demethylation the 7-methyl ether. This is definitely different from oroxylin-A. The use of anisic anhydride in the above condensation yields two products, (1) 7∶4′-dimethyl ether of scutellarein and (2) 5∶7∶4′-trimethyl ether of 3-anisoyl-scutellarein. The former is different from the 6∶4′-dimethyl ether obtained from natural sources.

A satisfactory procedure for the preparation of 2-hydroxy-ω∶3∶6-trimethoxy-4-benzyloxy-acetophenone is described. Oxidation of this to the 2∶5-dihydroxyketone (IV), its condensation with the anhydride and sodium salt of benzoic acid and subsequent demethylation yield 6∶8-dihydroxygalangin. This constitutes a simplified method for the synthesis of 5∶6∶7∶8-hydroxyflavonols and their methyl ethers.

Since there was an element of uncertainty in the methods employed in the past for the synthesis of 5∶7∶8-hydroxyflavone derivatives, an unambiguous method has now been worked out. The required ketone, 2-hydroxy-3∶4∶6-trimethoxyacetophenone has been prepared by the partial methylation of 2∶4-dihydroxy-3∶6-dimethoxyacetophenone which is obtained directly from 1∶4-dimethoxy-2∶6-dibenzyloxybenzene by the Hoesch reaction. It has been converted into 5∶7∶8-trimethoxyflavone (wogonin-dimethyl ether) and 5∶7∶8∶4′-tetramethoxyflavone by the Baker-Venkataraman procedure. Even the above dihydroxyketone could be used for this purpose fairly satisfactorily and it yields as an intermediate stage 5∶8-dimethoxy-7-hydroxyflavone. Demethylation with hydrodic acid even under mild conditions is not satisfactory. Nor-wogonin is best obtained by employing anhydrous aluminium chloride in benzene solution for this reaction.

The method of demethylation using aluminium chloride in benzene medium is shown to be applicable to polymethoxy flavanones. 5∶7∶4′-, 5∶7∶8- and 5∶6∶7-trimethoxy flavanones yield the corresponding trihydroxy compounds. Similarly carthamidin and isocarthamidin are obtained from their tetramethyl ethers whose synthesis is described. This work provides synthetic confirmation of the constitution of these tetrahydroxy flavanones proposed by Kuroda. That no isomeric change takes place in the preparation of carthamidin is established by its methylation to its tetramethyl ether.