Halogen redistribution reactions between alkyl halides and trimethylsilyl iodide

Abstract Trimethylsilyl iodide has been found to react rapidly at 50°C with 1-fluorooctane, 2-fluorooctane and benzyl fluoride to produce the corresponding octyl or benzyl iodides and trimethylsilyl fluoride. Also, it reacts rapidly and cleanly with t-butyl chloride or bromide to form t-butyl iodide. However, it does not react readily with the 1-octyl, 2-octyl, benzyl or allyl chlorides or bromides. We have discovered that tetra-n-butylammonium iodide catalyzes the reactions of primary alkyl chlorides or bromides with trimethylsilyl iodide, and molecular iodine catalyzes the reactions of secondary and tertiary alkyl chlorides and bromides. However, tetra-n-butylammonium iodide slows down the reactions of secondary and tertiary alkyl chlorides and bromides. Mechanistic pathways are suggested for each of the various types of halogen redistribution processes encountered.