Synthesis of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines

• Ksenia I. Kaskevich,
• Anastasia A. Babushkina,
• Vladislav V. Gurzhiy,
• Dmitrij M. Egorov,
• Nataly I. Svintsitskaya and
• Albina V. Dogadina

Beilstein J. Org. Chem. 2020, 16, 1947–1954, doi:10.3762/bjoc.16.161

• observed in the case of 6-trifluoromethyl-2-thiouracil that afforded 2- and 3-phosphonylated 5-oxothiazolopyrimidines in a 1:1 ratio. Keywords: chloroethynylphosphonate; heterocyclization; phosphonylated thiazolopyrimidines; phosphonylation; thiazolopyrimidine; 2-thiouracil; Introduction

• thiazolopyrimidine-5-ones by reacting 6-methyl-2-thiouracils with bromoethynylketones has been reported by Shishkin and co-workers (Scheme 4) [20]. The authors for the first time proved the structure of the 5-oxo isomer by single crystal X-ray diffraction analysis. The Pd-catalyzed Sonogashira coupling reaction

• . As the second reaction component, available 2-thiouracils were chosen as the most studied objects used for creating thiazolopyrimidine systems. The main objective of the study was to determine the regioselectivity of the reaction. Literature data mainly report the formation of 5-oxopyrimidines by

Synthesis of diverse dihydropyrimidine-related scaffolds by fluorous benzaldehyde-based Biginelli reaction and post-condensation modifications

• Bruno Piqani and
• Wei Zhang

Beilstein J. Org. Chem. 2011, 7, 1294–1298, doi:10.3762/bjoc.7.150

• are used as common intermediates for post-condensation modifications such as cycloaddition, Liebeskind–Srogl reaction and Suzuki coupling to form biaryl-substituted dihydropyrimidinone, dihydropyrimidine, and thiazolopyrimidine compounds. The high efficiency of the diversity-oriented synthesis is

• diversity-oriented synthesis of biaryl-substituted dihydropyrimidinone 5, thiazolopyrimidine 6, and dihydropyrimidine 7 compounds (Scheme 1). The perfluorooctanesulfonyl-attached benzaldehydes 1 were used as a key component for the Biginelli reactions [6]. The Biginelli products 4 were used as a common

• effort was to convert them to thiazolopyrimidine through cyclocondensation with chloroacetone [16][17]. The reaction was performed in water under microwave heating at 120 °C for 30 min to afford thiazolopyrimidines 8a and 8b in 89% and 85% yields, respectively, after F-SPE. Suzuki reactions of 8a and 8b