Abstract
Syntheses of 3,8-dihydro-1,3,6,8-tetramethylpyrimido[4,5,6-gh]perimidine-2,7-1H,6H)-dione (2), 1,2,3,6,7,8-hexahydro-1,3,6,8-tetramethylpyrimido[4,5,6-gh]perimidine (3), and 3,6,7,8-tetrahydro-1,3,6,8-tetramethylpyrimido[4,5,6-gh]perimidin-2(1H)-one (4) are reported. The corresponding radical cations were generated by oxidation with iodine or tris(4-bromophenyl)amminium hexachlo-roantimonate and were studied by ESR and ENDOR for comparison with the 1,4,5,8-tetrakis-(dimethylamino)naphthalene radical cation (1.+). The ESR results of 2.+-4.+, however, give no indications which could explain the widely different exo (3.54 G) and endo (1.77 G) N-methyl proton splittings in 1.+.
