New and efficient synthesis of pyrrolo[3,2-b]pyrrole-2,5-diones by double-anion-capture reactions of ester carbanions with bis(imidoyl)chlorides of oxalic acid
P. Langer et al., New and efficient synthesis of pyrrolo[3,2-b]pyrrole-2,5-diones by double-anion-capture reactions of ester carbanions with bis(imidoyl)chlorides of oxalic acid, J ORG CHEM, 65(3), 2000, pp. 729-734
A variety of pyrrolo[3,2-b]pyrrole-2,5-diones were efficiently prepared by
a new domino-reaction of eater carbanions with oxalic acid-bis(imidoyl)chlo
rides, This reaction proceeded by condensation of 2 equiv of the ester with
the bis(imidoyl)chloride and subsequent intramolecular attack of the nitro
gen atoms of the bis-enamine intermediate onto the ester groups. The produc
ts, which can be regarded as dilactams of pentalene, represent useful synth
etic pigments due to their optical features, their stability, and low solub
ility. The W-vis properties of the pyrrolo[3,2-b] pyrrole-2,5-diones could
be efficiently controlled by the substituents attached to the heterocyclic
core. The scope and the limitations of the new cyclization reaction were in
vestigated.