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.

中文翻译：

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3（2）-膦酰基化的噻唑并[3,2-a]氧嘧啶的合成。

通过氯乙炔基膦酸酯与未取代的和5（6）-取代的2-硫尿嘧啶的反应，首次合成了一系列3（2）-膦酰化的噻唑并[3,2- a ]氧嘧啶。氯乙炔基膦酸酯与带有电子给体基团（CH ₃，Ph）的6-取代的2-硫尿嘧啶的反应具有高的区域选择性，涉及通过N ^3-氮原子环化形成新的3-膦酰基化的噻唑并[3,2- a ] -5-氧嘧啶具有良好的收率。对于未取代的5-甲基-2-硫尿嘧啶，环化主要通过N ¹原子，部分通过N ^3-氮原子发生，从而形成相应的噻唑并[3,2-a ] -7-和5-氧嘧啶。在6-三氟甲基-2-硫氧嘧啶以1：1的比例提供2-和3-膦酰化的5-氧噻唑并嘧啶类化合物的情况下，观察到反应区域选择性的显着变化。