Dithionite‐Catalysed Addition of Perfluoroalkyl Iodides to Unsaturated Carbohydrates

The perfluoroalkyl chains (−C 4 F 9 , −C 6 F 13 , −C 8 F 17 ) were terminally connected to the 5‐enopyranose 1 , and the 5‐enofuranoses 8 and 23 by addition, in the presence of sodium dithionite, of the corresponding homologous perfluoroalkyl iodides to the double bond. Up to six products were separated from each reaction mixture and then fully characterised. The 5‐iodo derivatives 9 , 10 (prepared from 8 ), 24 , 25 , and 26 (prepared from 23 ) were diastereomeric mixtures (5 R ‐5 S ). Compounds 9 , 10 , and 25 were hydrodeiodinated to the methylene derivatives 17 , 18 , and 27 , respectively. Complete deprotection of the perfluoroalkyl‐substituted pyranose 3 (prepared from 1 ), and of the furanoses 17 and 18 led to the carbohydrate‐based amphiphilic mesogens 29 / 30 , 21 , and 22 , respectively, with a perfluoroalkyl tail. These formed mesophases of the smectic A type.