Aromatische Spirane, 21. Mitt [1]: Darstellung von Methylphthalaldehydsäuren und ihren Ethyl-und Methylestern als Synthone für Synthesen von methylierten 2,2′-Spirobiindandionen

Abstract

The isomeric methyl phthalaldehydic acids 11 were obtained from phthalides 4 by bromation (NBS) to the 3-bromo derivatives 7 and subsequent hydrolysis with water. 4 in turn were accessible from dimethyl methyl benzoates 1 by dibromination with NBS and subsequent thermical cyclization to the bromo derivatives 3 which, on catalytic dehalogenation, afforded the phthalides 4. Reaction of 11 with methanol or ethanol gave the pseudo-esters 13 and 14, resp. Short treatment of 11 with diazomethane on the other hand yielded the methyl formyl benzoates 15b to 15e. Prolonged reaction (several hours) gave the oxiranyl compounds 17; in addition, the acetonyl derivatives 18 were also found, obviously formed by a double methylene insertion into 15. All reactions proceeded with good to excellent yields.