Abstract
Upon treatment with benzylamine and n-propylamine, 10-thiaisoalloxazines 3 undergo a smooth ring-contraction initiated by nucleophilic addition of alkyl amines to the conjugated diimine bond in the molecule to give the corresponding 6'-substituted amino-spiro[benzothiazoline-2, 5'-pyrimidine-2', 4'(3'H, 5'H)-diones] 4, whereas thermal reaction of 3 with benzyl alcohol results in the preferential formation of the redox products, 1, 5-dihydro-10-thiaisoalloxazines (cf. 6) and benzaldehyde, proceeding via an initial one-electron transfer process.
