Nucleophiles containing two functional groups were added across the 5,6- and 7,8-bonds of ethyl pteridine-4-carboxylate. In some cases only one molecule of the addendum was involved and the products contained new heterocyclic systems with three or four rings. In other cases two molecules of the addendum added separately across the 5,6- and 7,8-bonds of the pteridine. Thus, ethylene glycol gave a 1,4-dioxinopteridine or a bis-(2-hydroxyethoxy)-adduct according to conditions. Ethane-1,2-dithiol, 1,2-diaminoethane and o-phenylenediamine gave 1,4-dithiino-, pyrazino-, and quinoxalino-pteridines respectively. 2-Thioethanol probably gave a 1,4-thioxino[2,3-g]pteridine rather than its [3,2-g] isomer. 2-Aminoethanol gave a bis-(2-hydroxyethylamino)-adduct.

U.v., ¹H n.m.r., and mass spectral data are presented.