[407-25-0] · C4F6O3 · Trifluoroacetic Anhydride-Sodium Iodide · (MW 210.04)
[7681-82-5] · INa · Trifluoroacetic Anhydride-Sodium Iodide · (MW 149.89)
(deoxygenation; converts alcohols to iodides)
Physical Data: see Trifluoroacetic Anhydride and Sodium Iodide.
The primary use for the combination of trifluoroacetic anhydride and sodium iodide is deoxgenation. It has also been used for the conversion of alcohols to iodides.
Sulfoxides are rapidly deoxgenated to sulfides by the use of trifluoroacetic anhydride with sodium iodide. The reaction proceeds instantaneously under cooling at 0 °C when trifluoroacetic anhydride is added to an acetone solution of the sulfoxide and sodium iodide. Dialkyl, alkyl/aryl, and diaryl sulfoxides are all deoxygenated with yields in excess of 90%, with reaction times less than 10 min (eq 1).
Epoxides are deoxygenated with retention of geometry by treatment with trifluoroacetic anhydride (1 equiv) and sodium iodide (4 equiv). Trifluoroacetyl iodide is generated in situ, which reacts with the epoxide in the presence of the excess sodium iodide to give the alkene. The yields are 77-95% after 24 h with a 1:1 mixture of MeCN and THF as solvent (eqs 2 and 3).
Primary and secondary alcohols are converted to the corresponding iodides in a one-pot two-step reaction. An intermediate trifluoroacetate is formed by reaction of the alcohol with trifluoroacetic anhydride and this is transformed into the halide via nucleophilic substitution with sodium iodide. Substituting sodium iodide with Lithium Iodide gives higher yields (eq 4). The corresponding chlorides and bromides may be synthesized by use of the appropriate sodium/lithium halide.
University of Bristol, UK