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Part-IISynthesis of Pyrimidinesyield 2-alkyl and arylthioquinazolinones (Table 20), as well as, 2-alkyl orarylthiothieno[2,3-d]pyrimidin-4-ones (Table 21), 2-alkylthiothieno[3,2-d]pyrimidin-4-ones (Table 22) and 2-alkylthiothieno[3,4-d]pyrimidin-4-ones (Table 25), which areotherwise accessible only through two step syntheses.OOOC 2 H 5dry HCl+ RXCNNH 2 NIa9aX = S, O2-Alkyl and arylthioquinazolinones (Table 20)NHXROOR 1R 1OC 2 H 5dry HCl+ RXCNR 2R 2NH 2SSIbNHN XR9bX = S, O2-Alkyl and arylthiothieno[2,3-d]pyrimidin-4-ones (Table 2), 2-alkylthiothieno[3,2-d]pyrimidin-4-ones (Table 3) and 2-alkylthiothieno[3,4-d]pyrimidin-4-ones (Table 25).Similarly, simple cyanamide and dialkyl cyanamides yield 2-amino- and 2-dialkylaminothieno[2,3-d]pyrimidin-4(3H)-ones (Table 26) under these reactionconditions. However when N-monoaryl cyanamides were used two isomericthienopyrimidin-4-ones Ii and Ij have been obtained as the condensation products of theirdry HCl catalyzed reaction with thiophene o-aminoesters 9b. The reaction proceeds viathe transient guanidine intermediate, which cyclizes through two alternate pathways toafford the isomeric 2-aminothieno[2,3-d]pyrimidin-4-ones. (Scheme 4) (Tables 26 and27). 26,33236