TY - JOUR A1 - Kaskevich, Ksenia I. A1 - Babushkina, Anastasia A. A1 - Gurzhiy, Vladislav V. A1 - Egorov, Dmitrij M. A1 - Svintsitskaya, Nataly I. A1 - Dogadina, Albina V. T1 - Synthesis of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines JF - Beilstein Journal of Organic Chemistry PY - 2020/// VL - 16 SP - 1947 EP - 1954 SN - 1860-5397 DO - 10.3762/bjoc.16.161 PB - Beilstein-Institut JA - Beilstein J. Org. Chem. UR - https://doi.org/10.3762/bjoc.16.161 KW - chloroethynylphosphonate KW - heterocyclization KW - phosphonylated thiazolopyrimidines KW - phosphonylation KW - thiazolopyrimidine KW - 2-thiouracil N2 - A series of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines was synthesized for the first time by the reactions of chloroethynylphosphonates with unsubstituted and 5(6)-substituted 2-thiouracils. The reaction of chloroethynylphosphonates with 6-substituted 2-thiouracils bearing electron-donor groups (CH3, Ph) proceeded with high regioselectivity involving the cyclization through the N3-nitrogen atom to form new 3-phosphonylated thiazolo[3,2-a]-5-oxopyrimidines with good yield. In the case of unsubstituted and 5-methyl-2-thiouracils, cyclization occurred predominantly through the N1 atom and partially via the N3-nitrogen atom to form a mixture of the corresponding thiazolo[3,2-a]-7- and 5-oxopyrimidines. A dramatic change in the reaction regioselectivity was observed in the case of 6-trifluoromethyl-2-thiouracil that afforded 2- and 3-phosphonylated 5-oxothiazolopyrimidines in a 1:1 ratio. ER -