Abstract: Despite 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 2π 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 systems through 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.

Reactivity and Synthetic Applications of 4,5-Dicyanopyridazine: an Overview / R. Alfini; M. Cecchi; D. Giomi. - In: MOLECULES. - ISSN 1420-3049. - ELETTRONICO. - 15:(2010), pp. 1722-1745. [10.3390/molecules15031722]

Reactivity and Synthetic Applications of 4,5-Dicyanopyridazine: an Overview

ALFINI, RENZO;CECCHI, MARCO;GIOMI, DONATELLA
2010

Abstract

Abstract: Despite 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 2π 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 systems through 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.
2010
15
1722
1745
R. Alfini; M. Cecchi; D. Giomi
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/393847
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