Reaction of several Vilsmeier reagents with 5-amino-2,3-dihydro[1]benzofuro[3,2-b]oxepin-4-carbonitrile gave tetracyclic 2-substituted 4-chloro-5,6-dihydro[1] benzofuro[3',2':2,3]oxepino[4,5-d]pyrimidines. The structure of one of these, the 4-chloro-2-phenyl derivative, was confirmed by X-ray crystallography. Treatment of the 4-chloro derivatives with simple amines as nucleophile afforded 2-substituted 4-amino derivatives. A pentacyclic compound was also obtained by dehydrative ring closure. These products were evaluated for antiplatelet activity, and some showed potency comparable with that of aspirin.