Preparation in two steps: First, reaction of isobutyric acid with 2,4,6-trimethoxytoluene (m.p. 24–26°) in the presence of boron trif luoride. Then, the complex obtained* (76%, m.p. 180°) was hydrolyzed in dilute methanol at 50° for 1 h (96%)
2,2-Difluor-1,2-dihydro-4-isopropyl-5,7-dimethoxy-8-methyl-1-oxa-3- oxonia-2-boratanaphthalin (5a) (in german).
