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Unusual Reactions Between Aromatic Carbon Supernucleophiles and 1,2‐Diazabuta‐1,3‐dienes: Useful Routes to New Pyrazolone and Cinnoline Derivatives
Author(s) -
Forlani Luciano,
Attanasi Orazio A.,
Boga Carla,
De Crescentini Lucia,
Del Vecchio Erminia,
Favi Gianfranco,
Mantellini Fabio,
Tozzi Silvia,
Zanicola
Publication year - 2008
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200800445
Subject(s) - chemistry , cinnoline , sodium methoxide , medicinal chemistry , electrophile , pyrazolone , methoxide , reagent , semicarbazone , organic chemistry , methanol , catalysis
Reactions between 1,3,5‐tris(dialkylamino)benzenes and 1,2‐diazabuta‐1,3‐dienes produce semicarbazone derivatives through attack of the supernucleophile aromatic carbon atom at the terminal carbon atom of the heterodiene reagent. The strong activation of the aromatic ring due to the presence of the three amino groups in a symmetrical relationship promotes electrophilic aromatic substitution by the neutral carbon atom of the electrophile. The resulting semicarbazones, in methanol in the presence of sodium methoxide, mainly afford pyrazolone derivatives, whereas in THF in the presence of sodium methoxide an unusual cyclization reaction produces cinnoline derivatives as the major products. Both cyclization reaction mechanisms are discussed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)