Syntheses, structures, and stabilities of aliphatic and aromatic fluorous iodine(I) and iodine(III) compounds: the role of iodine Lewis basicity

• Published in: Beilstein journal of organic chemistry 2017-11, Vol.13 (1), p.2486-2501
• Main Authors: Mukherjee, Tathagata, Biswas, Soumik, Ehnbom, Andreas, Ghosh, Subrata K, El-Zoghbi, Ibrahim, Bhuvanesh, Nattamai, Bazzi, Hassan S, Gladysz, John A
• Format: Article
• Language: English
• Subjects: Acetone; Alcohols; Chemistry; chlorination; copper mediated perfluoroalkylation; Crystal structure; DFT calculations; fluorous; Free radicals; Full Research Paper; hypervalent iodine; Iodine; nucleophilic substitution; polar space group; Pyridines; Solvents
• ISSN: 1860-5397; 2195-951X; 1860-5397
• DOI: 10.3762/bjoc.13.246

The title molecules are sought in connection with various synthetic applications. The aliphatic fluorous alcohols R CH OH (R = CF (CF ) ; = 11, 13, 15) are converted to the triflates R CH OTf (Tf O, pyridine; 22-61%) and then to R CH I (NaI, acetone; 58-69%). Subsequent reactions with NaOCl/HCl give iodine(III) dichlorides R CH ICl ( = 11, 13; 33-81%), which slowly evolve Cl . The ethereal fluorous alcohols CF CF CF O(CF(CF )CF O) CF(CF )CH OH ( = 2-5) are similarly converted to triflates and then to iodides, but efforts to generate the corresponding dichlorides fail. Substrates lacking a methylene group, R I, are also inert, but additions of TMSCl to bis(trifluoroacetates) R I(OCOCF ) appear to generate R ICl , which rapidly evolve Cl . The aromatic fluorous iodides 1,3-R C H I, 1,4-R C H I, and 1,3-R C H I are prepared from the corresponding diiodides, copper, and R I (110-130 °C, 50-60%), and afford quite stable R C H ICl species upon reaction with NaOCl/HCl (80-89%). Iodinations of 1,3-(R ) C H and 1,3-(R CH CH ) C H (NIS or I /H IO ) give 1,3,5-(R ) C H I and 1,2,4-(R CH CH ) C H I (77-93%). The former, the crystal structure of which is determined, reacts with Cl to give a 75:25 ArICl /ArI mixture, but partial Cl evolution occurs upon work-up. The latter gives the easily isolated dichloride 1,2,4-(R CH CH ) C H ICl (89%). The relative thermodynamic ease of dichlorination of these and other iodine(I) compounds is probed by DFT calculations.