Diiodomethane: A Versatile C1 Building Block

Abstract

Diiodomethane, better known as methylene iodide, is a dense (3.325 g/mL at 25˚C), light-sensitive, pale-yellow liquid. Because of its high density, it is used by the gemo­logical industry to determine the density of minerals.[1] Being such an interesting compound, diiodomethane is a versatile C1 building block, which can be used to form carbon–carbon and carbon–heteroatom bonds. It is an easy-to-handle compound and can be used in a wide number of different reactions such as epoxidation,[2] diazotization,[3] iodomethylation,[4] cyclopropanation,[5] alkene reduction,[6] and sigmatropic rearrangement.[7] In the presence of metallic samarium, the air-sensitive samarium diiodide (SmI2) is formed in situ; this is cheaper than buying samarium diiodide.[8]