Preparation of Oligo(ethylene glycol)-Terminated Icosanedisulfides

Abstract

This paper describes the synthesis of hexa(ethylene glycol) and carboxymethylhexa(ethylene glycol)-terminated alkane­disulfides 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.

Key words

Grignard reaction - oligo(ethylene glycol) - thiols - carboxylic acids - self-assembled monolayers

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10

In light of our subsequent experience with the synthesis of disulfide 7, we believe that the milder base K₂CO₃ is probably more appropriate than LiOH for this transformation.