Room‐Temperature Electrophilic 5‐endo‐dig Chlorocyclization of Alk‐3‐yn‐1‐ones with the Use of Pool Sanitizer: Synthesis of 3‐Chlorofurans and 5‐Chlorofuropyrimidine Nucleosides

The 5‐endo‐dig chlorocyclization of 1,4‐disubstituted alk‐3‐yn‐1‐ones (propargylic ketones) with the use of trichloro‐s‐triazinetrione (trichloroisocyanuric acid, TCCA; 0.4 equiv.) in toluene, at room temperature, in the absence of base, provides 2,5‐disubstituted 3‐chlorofurans in high yields (79–96 %). The reaction can be accomplished by using commercially available swimming pool sanitizer. Selected 3‐chlorofuran was validated as a substrate for Suzuki–Miyaura coupling. In a similar manner, chlorocyclization of 5‐alkynyl‐2′‐deoxyuridines produces 5‐chlorofuropyrimidine nucleosides (76–83 %), which are analogues of potent anitviral agents. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)