Intramolecular cycloaddition reactions of mono- and di-hydroxypyrimidines

Abstract

The intramolecular cycloaddition of unactivated olefins to dihydroxypyrimidines is described. The primary bridged cycloadducts may be isolated and hydrolysed, the overall process resulting in functionalisation of the olefin. The nitrile derivative (18)[4-hydroxy-2-methyl-6-oxo-5-(3-cyanopropyl)-1,6-dihydropyrimidine] also undergoes cycloaddition, althought the primary adduct (19) is unstable and elimination of isocyanic acid occurs to form an annelated monohydroxypyrimidine (20). Olefins also react in an intramolecular fashion with monohydroxypyrimidines, the intermediate bicyclic adducts readily undergoing a subsequent retro-Alder reaction to yield annelated pyridines.