Efficient synthesis of 2,6-dioxo-1,2,3,4,5,6-hexahydroindoles based on the synthesis and reactions of (2,4-dioxocyclohex-1-yl)acetic acid derivatives

Acetal-protected (2,4-dioxocyclohex-1-yl)acetic acid derivatives were prepared by the allylation of dilithiated 1,3-cyclohexane-1,3-diones, by the protection of the carbonyl groups and by the oxidation of the alkene. The products were then transformed, by amide formation and subsequent cyclization, into 2,6-dioxo-1,2,3,4,5,6-hexahydroindoles, which represent important intermediates for the synthesis of various alkaloids.