Derivate des Benzo[1.3]dioxols, 431 Über Benzo [1.3] dioxolcarbonsäuren / Derivatives of 1,3-Benzodioxoles, 43 1,3-Benzodioxolecarboxylic Acids

We describe the possibilities of formation and preparation of the “natural” 1,3-benzodioxolecarboxylic acids 1, 2, 4, 6 b, and 7, already mentioned in literature. Myristic acid (3e) was prepared in good yield from 3-methoxy-4,5-dihydroxy-benzoic acid ester (3c) , which could be easily made from 3-methoxy-2,3-carbonyldioxy-benzoic acid methylester (3b). Myristicic acid methylester (3d) could be subjected to methylation and hydrolysis leading to 3e without any difficulties. 4.6-dimethoxy-1,3-benzodioxole-5-carboxylic acid (5b) was prepared in good yields by oxidation of 4,6-dimethoxy-1,3-benzodioxole-5-aldehyde (5a). 5.7-dimethoxy-1,3-benzodioxole-carboxylic acid (13f), one of the “unnatural” 1,3-benzodioxolecarboxylic acids, derivatives of o-ipiperonylic acid (8), was prepared from 5-amino-7-methoxy-1,3- benzodioxole-4carboxylic acid methyl ester (13b) by diazotisation, elimination of nitrogen, methylation, and hydrolysis. A comparison of our measured pkA-values showed the strongest acidity belonging to 5,6-dimethoxy-1,3-benzodioxole-4-carbocylic acid (11).