Reactions of Cyclic Oxalyl Compounds XXXIX [1]. Reactions of 4-Ethoxycarbonyl-5-phenyl-2,3-dihydrofuran-2,3-dione with Heterocumulenes and Schiff Bases

Article abstract of DOI:10.1007/BF00810774

Furan-2,3-dione 1 reacts with arylisocyanates to the corresponding pyrrol-2,3-diones 2, whereas conversion with diisopropylcarbodiimide affords the oxazepin-6,7-dione derivative 3 in 68% yield. 1,3-Oxazines 5, 6, and 7 were obtained by thermolysis of 1 in boiling xylene in presence of arylisocyanates, diphenylketen-p-tolylimine, and Schiff bases, most likely by trapping the α-oxoketene intermediate 4. Preparative flash vakuum pyrolysis (FVP) of 1 and 2b gave 8 and 9, respectively.