Phthalide dehydration

Condensation of an appropriately substituted phenylacetic acid with phthalic anhydride in the presence of sodium acetate leads to aldol-like reaction of the methylene group on the acid with the carbonyl on the anhydride. Dehydration followed by decarboxylation of the intermediate affords the methylenephthal-ides (12). Treatment of the phthalides with base affords directly the indandiones, probably via an intermediate formally derived from the keto-acid anion (13). The first agent of this class to be introduced was phenindandione (14) this was followed by anisindandione (1S) and chlorindandione (16). ... 

Most of the stable isobenzofurans are 1,3-diaryl substituted, and are deep yellow. Such compounds are available via the partial reduction, and dehydrating cyclisation of 1,2-diaroylbenzenes. Both 1-mono- and 1,3-disubstituted isobenzofurans are available from phthalides by Grignard addition then ehmination of water. ... 

Potassium tert-butoxide Self-condensation of phthalides with subsequent dehydration... 

The synthesis of 13-hydroxylated tetrahydroprotoberberines from norphthalideisoquinolines has been achieved. Catalytic reduction of the phthalide-isoquinoline 32, derived from papaverine (see Sec. 24.2.3), afforded a separable mixture or erythro- and /Areo-norphthalideisoquinolines. Base-catalyzed lacta-mization followed by lithium aluminum hydride reduction of the threo-nov and rj fAro-norphthalides yielded the 13 - and 13a-hydroxytetrahydroprotober-berines, respectively. The hydroxylactam derived from the / r o-norphthalide tends to dehydrate readily to the oxoprotoberberine system (see Scheme 19.4). ... 

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