G S Krishna Rao
Articles written in Proceedings – Section A
Volume 27 Issue 4 April 1948 pp 245-257
Using typical examples, some of which are new, oxidative demethylation of methoxy benzenes, ketones, chalkones and flavones with nitric acid is discussed. The flavones without exception undergo simple conversion into para quinones. The others fall into two categories: (
Under favourable conditions hydroxy quinones can be methylated by means of dimethyl sulphate and potassium carbonate to the corresponding methyl ethers,
Volume 28 Issue 3 September 1948 pp 103-110
An essential point which has not been established in a simple manner by the previous study of pedicinin and its synthesis relates to the position of the methoxyl group. This has now been settled in an unambiguous manner by the reduction of pedicinin with stannous chloride to dihydropedicinin and its ethylation. The product is found to be identical with 4-methoxy-2∶3∶5∶6-tetraethoxy chalkone obtained synthetically starting from 2∶6 dimethoxy quinol. This chalkone undergoes oxidative de-ethylation with nitric acid yielding ethyl pedicinin and eventually pedicinin.
The toxic properties of dimethyl pedicinin (2∶4∶5-trimethoxy-quino chalkone) have been studied using fish.
Volume 28 Issue 4 October 1948 pp 198-209
Though despedicellin and dihydropedicinin are prepared from chalkones and were earlier given the chalkone constitution, their properties indicate that they are flavanones. This constitution is also in accordance with the recent discovery of the new effect of hydrogen bonds on the stability of flavanones. It is confirmed by the following experiments. (1) The two compounds undergo partial methylation with diazomethane yielding 5-hydroxy-6: 7∶8-trimethoxy-flavanone which forms with nitric acid 6∶7-dimethoxy-quinoflavanone identical with the sample obtained from 5∶6∶7∶8-tetramethoxy flavanone. (2) Dihydropedicinin undergoes oxidation with