Lactone, 16. Mitt.: Synthese von 4,9-Dihydropyrano[3,4-b]indol-1(3H)-onen aus α-Ethoxalyl-δ-valerolacton

Lactones, XVI: Synthesis of 4,9-Dihydropyrano[3,4-b]indol-1(3H)-ones from α-Ethoxalyl-δ-valerolactone Treatment of α-ethoxalyl-δ-valerolactone (1) with diazotized anilines and indolization of the intermediate hydrazones 4 leads to the pyranoindolones 5 . Compared to the recently reported reaction of α-ethoxalyl-γ-butyrolactone with arylhydrazines²⁾, this synthesis is more versatile with regard to variation of substituents at the aromatic ring. Stereochemistry and reactivity of the α-arylhydrazonolactones are discussed.