Aromatische Spirane, 21. Mitt: Darstellung von Methylphthalaldehydsäuren und ihren Ethylund Methylestern als Synthone für Synthesen von methylierten 2,2′-Spirobiindandionen

Summary The isomeric methyl phthalaldehydic acids11 were obtained from phthalides4 by bromation (NBS) to the 3-bromo derivatives7 and subsequent hydrolysis with water.4 in turn were accessible from dimethyl methyl benzoates1 by dibromination withNBS and subsequent thermical cyclization to the bromo derivatives3 which, on catalytic dehalogenation, afforded the phthalides4. Reaction of11 with methanol or ethanol gave the pseudo-esters13 and14, resp. Short treatment of11 with diazomethane on the other hand yielded the methyl formyl benzoates15b to15e. Prolonged reaction (several hours) gave the oxiranyl compounds17; in addition, the acetonyl derivatives18 were also found, obviously formed by a double methylene insertion into15. All reactions proceeded with good to excellent yields.