Preparation of oligo(ethylene glycol)-terminated icosanedisulfides

This paper describes the synthesis of hexa(ethylene glycol) and carboxymethylhexa(ethylene glycol)-terminated alkane-disulfides 4 and 7, respectively, in which the alkylene chains are twenty-methylenes-long. The key twenty-carbon synthon, 20-bromoicos-1-ene (1), was prepared by homologation of 8-bromooct-1-ene, which was achieved via Cu(II)-catalyzed coupling of the corresponding Grignard reagent with 1,12-dibromododecane. Compounds 4 and 7 are expected to yield self-assembled monolayers (SAMs) that are more stable and well-ordered than those formed by their traditional undecane homologues.