Methods of nuclear oxidation are applied for the preparation of chromone derivatives, many of which have been required for the study of isomeric change. Just as in the flavone group the presence of a methoxyl (hydroxyl) in the 3-position prevents isomeric change from the 5:7:8 to the 5:6:7 arrangement of hydroxyl groups; in its absence the isomeric change takes place.

When boiled with hydriodic acid, 2:3-dimethyl-5:7:8-trimethoxy chromone undergoes besides demethylation, isomeric change also, yielding 2:3-dimethyl-5:6:7-trihydroxy chromone, thus showing that a free hydrogen atom in the 3-position is not essential for this isomeric change to take place and that the nature of the substituent is also important. For purposes of comparison, 2:3-dimethyl-5:7:8-trihydroxy chromone has been obtained by demethylation of the above trimethyl ether with aluminium chloride and 2:3-dimethyl-5:6:7-trimethoxy chromone by independent synthesis using nuclear oxidation as a stage.

A new method of conversion of visnagin into kellin is described. It involves only three steps and gives much better yields. Nor-visnagin is subjected to nuclear oxidation with alkaline persulphate to yield nor-kellin which is conveniently methylated to kellin by means of dimethyl sulphate and potassium carbonate in acetone solution.

A review of ring isomeric change of flavones and chromones is made as also of the reactivity of C-hydroxy phloroglucinol and C-hydroxy phloracetophenone derivatives in methylation, benzoylation and ring closure. The results are consistent showing the greater reactivity of a hydroxyl group of the quinol unit as compared with that of the catechol unit. A tentative explanation is given.

A synthetic study has been made of the chromones ofEugenia caryophyllata. All the intermediates in the synthesis of eugenitin have now been isolated and fully characterised. A convenient route for the preparation of the starting material for this synthesis,viz., 3-methyl phloracetophenone has now been found. Two new syntheses of eugenin are also recorded. The observation of Schmid and Bolleter that eugenitin (6-methyl) undergoes change into isoeugenitol (8-methyl) when demethylated with boiling hydriodic acid and that isoeugenitin methyl ether (8-methyl) does not undergo isomeric change under the same conditions, is confirmed. This is the reverse of what has been observed in the case of C-hydroxy phloracetophenone derivatives. Further it is extraordinary because C-methyl phloroglucinol and C-methyl phloracetophenone behave like the C-hydroxy (methoxy) compounds in methylations and chromone ring closure.

An attempt has been made to develop a comprehensive scheme of biogenesis which includes all the five components occurring inEugenia caryophyllata. The basic compound is taken to be nor-eugenone and all the stages are based on analogy with laboratory experiments.

A number of α-methyl-furano-flavones and their dihydro derivatives have been prepared using 7-hydroxy-8-allyl flavone derivatives. Ring closure is effected with anhydrous hydrogen bromide followed by pyridine and dehydrogenation with N-bromosuccinimide. 2-Methyl cromone derivatives have also been made. Tests with fish of select compounds indicate that dihydrofurano compounds are better poisons and an α-methyl group reduces toxicity in the furano compounds.

In order to get fuller information on the influence of hydroxyl groups on alkali colour reactions a number of flavonols of types uncommon in Nature have been prepared and examined. Though the correlation between structure and alkali colour reactions is complex, when applied with care the reactions can be used for diagnostic purposes. The alkali colour reactions of the flavonols with 2′∶3′ and 2′∶3′∶4′ disposition of hydroxyl groups are not prominent and their fluorescence properties are also very feeble.