Realtime copper(I) triflate

Realtime copper(I) triflate
05 February 2021 - Electrochemistry

The Willans group (University of Leeds) report a new way to handle copper(I) triflate in organic reactions (Nicholls et al. DOI). This compound is the lesser known sibling of copper(II) triflate which is a general purpose reagent. Both act as Lewis acids, the copper(I) compound is more reactive but also more expensive and prone to degradation, oxygen or moist will bring about oxidation to the copper(II) compound. The Willans approach is electrochemical, triflic acid, a copper electrode and current enables in-situ generation of the catalyst with only byproduct hydrogen gas evolution.

Case at hand was the aerobic oxidation of alcohols to aldehydes. A 2013 Organic Syntheses prep (DOI) details the conversion of a benzyl alcohol with tetrakisacetonitrile copper(I) triflate (commercially sourced) , TEMPO, bipyridine and N-methyl imidazole in acetonitrile with exposure to air.

In the 2021 modification, the catalyst was generated from a copper electrode under an argon blanket in a continuous flow reactor with a 2.2 F per mole efficiency. The authors point out the triflic acid had to be completely reacted as it would neutralize the imidazole base. With the modification the aldehyde yield jumped from 89% to 98%.

The article mentions a resurgence in electrochemistry. Last year the same group published an extensive DIY electrochemistry tutorial in Green Chemistry here , open access!