Wydział Chemii

A. Sniady

A. Durham

M. S. Morreale

Andrzej Marcinek

Sławomir Szafert

Tadeusz Lis

K. R. Brzezińska

T. Iwasaki

T. Ohshima

K. Mashima

Roman Dembiński

2008

Journal of Organic Chemistry

73

5881-5889

10.1021/jo8007995

Naukowa

Angielski

Artykuł

5-Endo-dig cycloisomerization of 1,4- and 1,2,4- mostly aryl-substituted but-3-yn-1-ones in the presence of a catalytic amount of zinc chloride etherate (10 mol %) in dichloromethane at room temperature gave 2,5-di- and 2,3,5-trisubstituted furans in high yields (85−97%). DSC studies confirmed that a solely thermal process does not take place. A relevant catalytic process, employing μ-oxo-tetranuclear zinc cluster Zn₄(OCOCF₃)₆O, yielded bicyclic furopyrimidine nucleosides, when starting from acetyl-protected 5-alkynyl-2′-deoxyuridines (85−86%). Furopyrimidine was deprotected or simultaneously converted into pyrrolopyrimidine nucleoside. The time/concentration dependence for the reaction of 1-phenyl-4-(4-methylphenyl)butynone to 2-(4-methylphenyl)-5-phenylfuran displayed first-order kinetics with the rate dependent on catalyst concentration. The plot of ln k_obs versus ln[ZnCl₂] indicated first-order cycloisomerization, as referred to ZnCl₂ concentration, using both NMR and UV−vis reaction monitoring. The crystal structure of propyl furopyrimidine nucleoside (orthorhombic, P2₁2₁2₁, a/b/c = 5.684(2)/6.682(2)/36.02(2) Å, Z = 4) shows C2′-endo deoxyribose puckering, and the base is found in the anti position in crystalline form.

https://doi.org/10.1021/jo8007995

https://www.acs.org/content/acs/en.html