Reactivity and Synthetic Applications of 4,5-Dicyanopyridazine: An Overview†
AbstractDespite the poor reputation of electron-deficient pyridazines in intermolecular Hetero Diels-Alder (HDA) reactions, 4,5-dicyanopyridazine (DCP) showed a surprising reactivity as a heterocyclic azadiene in inverse electron-demand HDA processes with different dienophiles. The use of alkenes, alkynes and enamines as 2p electron counterparts afforded dicyanocyclohexa-1,3-dienes and substituted phthalonitriles, respectively, while the use of suitable bis-dienophiles provides a general strategy for the one-pot synthesis of polycyclic carbo- and hetero-cage systemsthrough pericyclic three-step homodomino processes. HDA reactions with heterocyclic dienophiles allowed direct benzoannelation: in particular, pyrrole and indole derivatives were converted to dicyano-indoles and -carbazoles. In addition an unprecedented reactivity of DCP as a very reactive heterocyclic electrophile at the C-4 carbon was also evidenced: by changing the experimental conditions, cyanopyrrolyl- and cyanoindolyl-pyridazines were obtained through reactions of pyrrole and indole systems as carbon nucleophiles in formal SNAr2 processes where a CN group of DCP acts as leaving group. Thus, careful control of the reaction conditions allows exploitation of both pathways for the synthesis of different classes of heterocyclic derivatives.
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Alfini, R.; Cecchi, M.; Giomi, D. Reactivity and Synthetic Applications of 4,5-Dicyanopyridazine: An Overview. Molecules 2010, 15, 1722-1745.
Alfini R, Cecchi M, Giomi D. Reactivity and Synthetic Applications of 4,5-Dicyanopyridazine: An Overview. Molecules. 2010; 15(3):1722-1745.Chicago/Turabian Style
Alfini, Renzo; Cecchi, Marco; Giomi, Donatella. 2010. "Reactivity and Synthetic Applications of 4,5-Dicyanopyridazine: An Overview." Molecules 15, no. 3: 1722-1745.