Cycloaddition of Carbodiimides with a Heteroaromatic Substituent to Allenic Acids

Article abstract of DOI:10.1002/hlca.19920750426

Cycloaddition of the allenic acid 3 with the N-cyclohexyl-N'-heteroaromatic carbodiimides 2a and 2b gave the isomeric pyrido<1,2-a>pyrimidones 4 and 5 and thiazolo<3,2-a>pyrimidones 6 and 7, respectively, instead of the expected Diels-Alder adducts analogues to 1.The compounds of the latter type, i.e. 8 and 9, were formed from 3 and carbodiimides 2c and 2d, respectively, containing an N'-(pyrazin-2-yl) or N'-(pyrimidin-2-yl)substituent.