Hindered Dialkyl Ether Synthesis via Electrogenerated Carbocations

Abstract

<p>Hindered ethers represent an underexplored area of chemical space due to the difficulty and inoperability associated with conventional reactions, despite the high-value of such structural motifs in a variety of societal applications. Demonstrated herein is an exceptionally simple solution to this problem that leverages the power of electrochemical oxidation to liberate high-energy carbocations from simple carboxylic acids. The controlled formation of these reactive intermediates takes place with low electrochemical potentials under non-acidic conditions to capture an alcohol donor thereby producing a range (>80) of ethers that would be extremely difficult to otherwise access. Simple nucleophiles can also intercept such cations, leading to hindered alcohols and even alkyl fluorides. This method has been field tested to solve the synthetic bottlenecks encountered on twelve real-world chemical scaffolds with documented societal impact, resulting in a dramatic reduction in step-count and labor required, accompanied with a higher yield (average step-count, time, and yield = 6.3, ca. 100 h, 19% vs. 1.5, 9.8 h, 43%). Finally, the use of molecular probes coupled to kinetic studies support the proposed mechanism and role of additives in the conditions employed.</p>

Metal‐ and Oxidant‐Free Electrosynthesis of Heterocycles from 1,2‐Diarylalkene Derivatives

“…Electrochemical measurements with cyclic voltammogram (Figure 1) revealed 4 a, 7 a, 9 a were prone to oxidation showing oxidation potential of 1.45 V, 1.18 V, 1.49 V (vs SCE) respectively whereas 1 a was prone to reduction (E p/2 red = À 0.50 V, À 0.94 V vs SCE). While distinct oxidation peak was not found for 1 a alone, adding 1 equivalent of 2,4,6-collidine which is a non-oxidizable base, [17] generated new oxidation peak at 1.10 V (vs SCE).…”