[Basic substituted thieno(3,4-d)pyrimidine carboxylic acids: synthesis via ANRORC-reaction starting from 7-cyanthieno(3,2-d)oxazines].

The synthesis of 7-cyan-thieno[3,2-d]-1,3-oxazine 7 is reported. Reaction of 7 with primary amines gives the thieno[3,4-d]pyrimidincarboxylic acids 14 in a unusual ring transformation. Several synthesized compounds were tested as antiallergic agents.