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New Cyclization Mode of [ N ‐(Diarylmethyleneamino)carbonimidoyl]ketenes: Synthesis of 9 H ‐Pyrazolo[3,2‐ b ][1,3]benzoxazines
Author(s) -
Lisowskaya Natalia A.,
Alajarin Mateo,
SanchezAndrada Pilar
Publication year - 2006
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.200500768
Subject(s) - decarbonylation , chemistry , pyrrole , ab initio , stereochemistry , medicinal chemistry , reaction mechanism , catalysis , organic chemistry
The thermal decarbonylation of methyl 3‐acyl‐1‐[ o ‐bromophenyl(phenyl)methyleneamino]‐4,5‐dioxo‐4,5‐dihydro‐1 H ‐pyrrole‐2‐carboxylates 2a and 2b gave the novel methyl 3‐acyl‐9‐hydroxy‐9‐phenyl‐9 H ‐pyrazolo[3,2‐ b ][1,3]benzoxazine‐2‐carboxylates 4a and 4b , the structures of which were determined by X‐ray crystallography. The proposed mechanism for this conversion, involving the [ N ‐( o ‐bromo‐α‐phenylbenzylideneamino)carbonimidoyl]ketenes 5 and the mesomeric betaines 6 as intermediates, has been investigated by ab initio and DFT calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)