Direct and indirect electrochemical generation of alkoxycarbenium ion pools from thioacetals

Abstract

a b s t r a c tThioacetals were found to be effective precursors to generate and accumulate alkoxycarbenium ions based on direct and indirect cation pool methods. Alkoxycarbenium ions thus generated reacted with carbon nucleophiles such as allylsilanes and enol silyl ethers to give C-C bond formation products in good yields.

Synthetic Organic Electrochemical Methods Since 2000: On the Verge of a Renaissance

“…507,508 This “ArS + cation pool” also found utility in the functionalization of arenes, allyl silanes, enol ethers, and ketene acetals (Figure 33B, middle); 511 moreover, it could be used to induce oxocarbenium formation through reaction with thioacetals (Figure 33B, right). 512–514 This process has found application in glycosylation chemistry where efficient protocols with flow reactors have been detailed. 515,516 Furthermore, the “ArS + cation pool” was utilized (in catalytic amounts) to initiate olefin cyclization reactions, forming both heterocyclic and carbocyclic rings (Figure 33C).…”

“…Nevertheless, due to the presence of disulfides in solution, treatment of the episulfonium with soft nucleophiles led to the formation of vicinal disulfides instead. Catalytic protocols have also been developed wherein substoichiometric amounts of the ArS + equivalent initiates a cation chain mechanism. , This “ArS + cation pool” also found utility in the functionalization of arenes, allyl silanes, enol ethers, and ketene acetals (Figure B, middle); moreover, it could be used to induce oxocarbenium formation through reaction with thioacetals (Figure B, right). − This process has found application in glycosylation chemistry where efficient protocols with flow reactors have been detailed. , Furthermore, the “ArS + cation pool” was utilized (in catalytic amounts) to initiate olefin cyclization reactions, forming both heterocyclic and carbocyclic rings (Figure C). , …”

Methods for 2-Deoxyglycoside Synthesis

“…In 2009, Yoshida and co-workers described the low-temperature observation of a pyranose-derived oxocarbenium cation in CH 2 Cl 2 using electrochemical oxidation (the cation pool method). 35 None of these systems, however, represented the glycosyl cation. Indirect evidence for the transient existence of the glycosyl cation came from the Yoshida lab using electrochemical activation of thioglycosides in flow systems, although the authors noted that this species could not be generated in batch reactors.…”

Electrogenerated Cationic Reactive Intermediates: The Pool Method and Further Advances

“…Yoshida and co-workers developed the indirect cation pool method for the generation, accumulation, and reactions of carboxonium ions (Scheme ). , In the indirect cation pool method, an active reagent is generated and accumulated electrochemically in the first step. In the second step, the active reagent is reacted with a precursor of the cation to generate and accumulate the cation.…”