Diiodosilane. 3. Direct Synthesis of Acyl Iodides from Carboxylic Acids, Esters, Lactones, Acyl Chlorides, and Anhydrides

Article abstract of DOI:10.1021/jo00299a042

Diiodosilane (SiH2I2, DIS) is a very useful reagent for direct, high yield synthesis of acyl iodides from variety of carboxylic acid derivatives, such as carboxylic acids, esters, lactones, anhydrides, and acyl chlorides.These transformations are remarkably accelerated by iodine.In the absence of iodine DIS reacts with carboxylic acids and esters, much as does iodotrimethylsilane (TMSI), to form the corresponding silyl carboxylates.However, in contrast to TMSI, DIS and iodine react further with silyl carboxylates to produce acyl iodides.This reaction, when followed by addition of an appropriate alcohol, represents an esterification and transesterification method that is useful even for sterically hindered and/or poorly nucleophilic alcohols.Lactones react with DIS to produce either silyl ω-iodo carboxylates or ω-iodoacyl iodides, depending on the reaction conditions.The reaction between DIS and 1 equiv of a carboxylic anhydride affords, in the presence of iodine, 2 equiv of acyl iodide.