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Cycloaddition Reaction of 2-Azadienes Derived from β-Amino Acids with Electron-Rich and Electron-Deficient Alkenes and Carbonyl Compounds. Synthesis of Pyridine and 1,3-Oxazine Derivatives

2002; American Chemical Society; Volume: 67; Issue: 7 Linguagem: Inglês

10.1021/jo016273+

1520-6904

Francisco Palácios, Esther Herrán, Gloria Rubiales, J.M. Ezpeleta,

Click Chemistry and Applications

Functionalized keto-enamines 6 were obtained by nucleophilic addition of enol ethers to the imine moiety of 2-azadienes derived from dehydroaspartic esters 4. Reactions of 2-azadiene 4c containing three electron-withdrawing substituents (CO(2)R) with enol ethers 5 in the presence of lithium perchlorate led to the formation of tetrahydropyridine derivatives 7 in a regio- and stereoselective fashion. 2H-[1,3]-oxazines 10 and pyridine derivatives 12 and 13 were obtained by heterocycloaddition reactions of electron-poor azadienes 4d-g containing two electron-withdrawing substituents (4-O(2)N-C(6)H(4), CO(2)R) in positions 1 and 4 with carbonyl derivatives (ethyl glyoxalate 9a and diethyl ketomalonate 9b) and the electron-deficient olefin tetracyanoethylene 11.