One-pot, one- and multi-carbon homologation of alkyl halides; reaction of grignard reagents with chloroiodomethane

Reaction of a Grignard reagent (RMgX) with chloroiodomethane affords the corresponding iodide (RI) and, depending on R, solvent, and temperature, iodides which are one-carbon and multicarbon homologs of RX. Allyl iodide but not allyl bromide can be monohomologated by the combined action of chloroiodomethane and isopropyl Grignard.