【文章名】Reaction of Cyclic Imidates with alpha,beta-Unsaturated Esters: Synthesis of New Pyrrolo[2,1-b]-1,3-oxazine and Pyrido[2,1-b]-1,3-oxazine Derivatives
[摘要]：The cycloaddition reaction of cyclic imidates, 2-benzyl-5,6-dihydro-4H-1,3-oxazines 1a-f, with dimethyl acetylenedicarboxylate 2, trimethyl ethylenetricarboxylate 4, or dimethyl 2-(methoxymethylene) malonate 6 afforded new fused heterocyclic compounds, such as methyl (6-oxo-3,4-dihydro-2H-pyrrolo[2,1-b]-1,3-oxazin-7-ylidene) acetates 3a-f (71-79%), dimethyl 2-(6-oxo-3,4,6,7-tetrahydro-2H-pyrrolo[2,1-b]-1,3-oxazin-7yl) malonates 5b-f (43-71%), or methyl 6-oxo-3,4-dihydro-2H,6H-pyrido[2,1-b]-1,3-oxazine-7-carboxylates 7a-f (32-59%), respectively. In these reactions, 1a-f (cyclic imidates, iminoethers) functioned as their N,C-tautomers (enaminoethers) 1' to alpha,beta-unsaturated esters 2, 4, and 6 to give annulation products 3, 5, and 7 following to the elimination of methanol, respectively.
