Synthesis of 4H-3,1-Benzoxazines, Quinazolin-2-ones, and Quinoline-4-ones by Palladium-Catalyzed Oxidative Carbonylation of 2-Ethynylaniline Derivatives

An effective and straightforward approach to the synthesis of 4H-3,1-benzoxazines 3 and 4, quinazolin-2-ones 5, and quinoline-4-one derivatives 6 and 7 is provided by palladium-catalyzed cyclization−alkoxycarbonylation of variously substituted 2-(trimethylsilanyl)ethynylaniline amide or urea derivat...

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Bibliographic Details
Published in:Journal of organic chemistry 2004-04, Vol.69 (7), p.2469-2477
Main Authors: Costa, Mirco, Cà, Nicola Della, Gabriele, Bartolo, Massera, Chiara, Salerno, Giuseppe, Soliani, Matteo
Format: Article
Language:English
Subjects:
Chemistry
Exact sciences and technology
Heterocyclic compounds
Miscellaneous
Organic chemistry
Preparations and properties
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Summary:An effective and straightforward approach to the synthesis of 4H-3,1-benzoxazines 3 and 4, quinazolin-2-ones 5, and quinoline-4-one derivatives 6 and 7 is provided by palladium-catalyzed cyclization−alkoxycarbonylation of variously substituted 2-(trimethylsilanyl)ethynylaniline amide or urea derivatives 2. Reactions are carried out in 7:1 MeCN/MeOH at 65 or 75 °C in the presence of catalytic amounts of 10% Pd/C in conjunction with Bu4NI and KF and under 2.4 MPa of a 3:1 mixture of CO and air. Anti and syn 6-exo-dig cyclization modes account for the formation of the two stereoisomers. Isomerization of the vinylpalladium intermediate may occur as well. Formation of a double carbonylation product 7r and of a gem-dimethoxycarbonylation product 6s, whose structures have been determined by X-ray diffraction analysis, is justified through an unusual type of rearrangement.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo0357770