Science of Synthesis

Heaney, H.; Christie, S., Science of Synthesis, (2004) 3, 599.

The thienylcopper reagent is useful as a mixed cuprate precursor when organolithium species are added to it, producing the mixed cuprate. The same reagent can also be reduced to an active copper(0) species, which will then react with alkyl halides to give a mixed cuprate.[‌436‌] This has advantages over the other Rieke copper-based methods discussed elsewhere in this chapter. These often require the use of phosphine-based ligands which could interfere with the workup. The thiophene makes isolation much more convenient. Initial investigations showed that (thienyl)Cu•LiCN can be reduced with lithium naphthalenide at low temperature in a short reaction time. This active species can then be used to react with alkyl halides. Insertion into the carbon—halogen bond produces a new mixed cuprate species, and this can then be employed in subsequent organic chemistry. Protonation of these simply gives the reduced alkyl halide in good yield. More useful is the reaction with acid chlorides, which produces ketones. Of note again in Rieke copper chemistry is the ability to carry sensitive functionality through a reaction scheme intact. In ‌Scheme 440‌, nitrile, halogen, and even epoxide functionality can all be employed in the alkyl halide portion of the reaction.

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