Preparation of uracil by cycloreversion. Structure of cycloalkane/ene‐ and norbornane/ene‐fused dihydrouracils

Publisher Website
Google Scholar
Abstract
The reactions of the 2‐amino‐1‐cycloalkane‐, cycloalkene‐, norbornane‐ and norbornenecarboxylates 1–9 with potassium cyanate gave urea esters, which were cyclized to cycloalkane‐, cycloalkene‐, norbornane‐ and norbornene‐fused 5,6‐dihydrouracils 10–17. On cyclization, the urea ester formed from trans‐4‐cyclohexene‐1‐carboxylate, furnished the cis‐fused 5,6‐dihydropyrimidine‐2,4(1H,3H)‐dione. On heating, the norbornene‐diexo‐fused dihydrouracil 16 yielded 2,4‐pyrimidinedione through the splitting‐off of cyclopentadiene. The structures of the compounds were proved by 1H and 13C nmr spectroscopy.