The cyclocondensation of 2-amino-5,6,7,8-tetrahydro-4H-cyclohepta[b]selenophene-3-carbonitrile (1) with formic acid and formamide gave the selenophenopyrimidine 15 and selenophenopyrimidone 6 derivatives. The reaction of 6 with phosphorus oxychloride produced 4-chloro-6,7,8,9-tetrahydro-5H-cyclohepta[4,5] seleno[2,3-d]pyrimidine (12), the key compound for our nucleophilic substitution reactions. The hydrazinoselenophenopyrimidine 19 obtained from the reaction of 12 with hydrazine hydrate was converted to its tetrazoloselenophenopyrimidine 21 and triazoloselenophenopyrimidine 26 derivatives. Moreover, the chloropyrimidine derivative was reacted with pyrrolidine and morpholine to afford 4-(1-pyrrolidinyl)-6,7,8,9-tetrahydro-5H-cylohepta[4,5]selenopheno [2, 3-d]pyrimidine (27) and 4- (6,7,8,9-tetrahydro-5H-cyclohept a [4,5]selenopheno [2,3-d]pirimidin-4-yl)morpholine (28). Anticancer activities of the synthesized compounds were investigated against the MCF-7 breast cancer cell line and the IC50 values of these compounds were in the range of 70.86-250.06 mu M.