ORGANOFLUORINE COMPOUNDS AND FLUORINATING AGENTS, 19 - DITHIONITE-CATALYZED ADDITION OF PERFLUOROALKYL IODIDES TO UNSATURATED CARBOHYDRATES

The perfluoroalkyl chains (-C4F9, -C6F13, -C8F17) were terminally conn ected to the 5-enopyranose 1, and the 5-enofuranoses 8 and 23 by addit ion, in the presence of sodium dithionite, of the corresponding homolo gous perfluoroalkyl iodides to the double bond. Up to six products wer e separated from each reaction mixture and then fully characterised. T he 5-iodo derivatives 9, 10 (prepared from 8), 24, 25, and 26 (prepare d from 23) were diastereomeric mixtures (5R/5S). 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 th e carbohydrate-based amphiphilic mesogens 29/30, 21, and 22, respectiv ely, with a perfluoroalkyl tail. These formed mesophases of the smecti c A type.