Untersuchungen zur Chemie von Isoindolen und Isoindoleninen, XXXV [1]. 1-Alkoxy-2-alkyl-2 H-isoindole — o-chinoide Hetarene mit unsymmetrischer Struktur / Studies on the Chemistry of Isoindoles and Isoindolenines, XXXV [1]. 1-Alkoxy-2-alkyl-2H-isoindoles — o-Quinonoid Hetarenes with Unsymmetric Structure

Abstract

3-Alkoxy-2-methyl-1 H-isoindolium salts have been prepared either via regioselective O-alkylation of the corresponding 2-alkyl-isoindoline-1-ones or via regioselective N-alkylation of 3-alkoxy-1 H-isoindoles with trialkyloxonium tetrafluoroborates or with alkyl trifluoromethanesulfonates. Deprotonation of these stable precursors leads to the generation of reactive 1-alkoxy-2-alkyl-2H-isoindoles in solution. Reactions with CC-dienophiles (N-substituted maleic imides) give rise to the formation of 1 : 2-adducts. The two step reaction comprises Michael-addition and Diels-Alderaddition; the isolation of an initially formed 1:1-adduct is possible in the case of steric hindrance. Constitution and configuration of a representative 1 : 2-adduct has been established by X-ray crystal structure determination.