Electrocatalysis as a key strategy for the total synthesis of natural products.

Electrochemical strategies have been a powerful approach for the synthesis of valuable intermediates, in particular heterocyclic motifs. Because of the mild nature, a wide range of nonclassical bond disconnections have been achieved via in situ-generated radical intermediates in a highly efficient manner. In particular, anodic electrochemical oxidative strategies have been utilized for the total synthesis of many structurally intriguing natural products. In this review article, we have discussed a number of total syntheses of structurally intriguing alkaloids and terpenoids in which electrochemical processes play an important role as a key methodology.

Oxidative electro-organic synthesis of dimeric hexahydropyrrolo-[2,3-b]indole alkaloids involving PCET: total synthesis of (±)-folicanthine.

An efficient electrochemical oxidation strategy for the total synthesis of a dimeric hexahydropyrrolo[2,3-b]indole alkaloid, (±)-folicanthine (1b), has been envisioned. Control experiments suggest that a PCET pathway involving stepwise electron transfer followed by proton transfer (ET-PT) was involved in the key oxidative dimerization process.

Electrochemical Synthesis of Dimeric 2-Oxindole Sharing Vicinal Quaternary Centers Employing Proton-Coupled Electron Transfer.

Dimerization of 3-substituted 2-oxindoles has been developed under a mild electrochemical condition, avoiding toxic chemical oxidants and metal by-products. This methodology forms a C(sp3)-C(sp3) bond at the pseudobenzylic position of two partners of 2-oxindoles with a broad substrate scope. These dimeric structural motifs are important building blocks for the total synthesis of pyrroloindoline alkaloids. Furthermore, this work demonstrates in-depth mechanistic insights employing electrochemistry, which suggests a stepwise one proton transfer (PT) and two electron transfer (ET) processes. Most significantly, reaction rate acceleration has been demonstrated by exploiting the base-assisted proton-coupled electron transfer (PCET) pathway. Hence, this work brings a new dimension in the field of electro-organic synthesis with the help of nature's favorite kinetic route, i.e., PCET, to lower the kinetic barrier.