Transition-Metal-Free C(sp³)–H Coupling of Cycloalkanes Enabled by Single-Electron Transfer and Hydrogen Atom Transfer

Abstract

Here we report a unique transition-metal-free C­(sp3)–H/C­(sp3)–H coupling of cycloalkanes at room temperature. Unactivated cycloalkanes and 2-azaallyls underwent the combination process of single-electron transfer (SET) and hydrogen atom transfer (HAT) to deliver a wide variety of cycloalkane-functionalized products. This expedient approach enables C­(sp3)–H/C­(sp3)–H coupling of cycloalkanes under mild conditions without transition metals, initiators, and oxidants.

Visible-Light-Driven C–S Bond Formation Based on Electron Donor–Acceptor Excitation and Hydrogen Atom Transfer Combined System

“…On the other hand, the reactive radical species can abstract a C­(sp 3 )–H hydrogen atom (hydrogen atom transfer: HAT − ) to give alkyl radical species. By utilizing these phenomena, novel photoreactions via EDA-SET and HAT combination are achieved. − …”

Transition-metal-free allylation of 2-azaallyls with allyl ethers through polar and radical mechanisms

“…Our team [62][63][64][65][66][67][68][69][70] and other groups [71][72][73][74][75][76][77][78][79][80][81][82][83][84] have been interested in the functionalization of 2-azaallyl anions through an umpolung strategy. Recently, we discovered and developed a unique radical generation approach 85 for the transition-metal-free C(sp 3 )-C(sp 2 ) (Fig.…”

Synthesis of Tryptamines from Radical Cyclization of 2-Iodoaryl Allenyl Amines and Coupling with 2-Azallyls

“…Panetti, Schelter, Walsh, and co-workers reported the solid-state structures and electrochemistry of the 2-azaallyl anions . Recently, Yang, Zhang, Walsh, and co-workers applied this unique radical generation and coupling strategy in the synthesis of benzofurylethylamines, isochromenylethylamines, and isoquinoline ethylamines using 2-iodo aryl allenyl ethers and amines as electron acceptors (Scheme c). − Cross-dehydrogenative coupling reactions were also introduced. , Additionally, Nishikata, Yazaki, Ohshima, and their co-workers used a copper-catalyzed generation of 2-azaallyl radicals to develop a synthesis of hindered α-amino acid derivatives. , …”

“…39−41 Cross-dehydrogenative coupling reactions were also introduced. 42,43 Additionally, Nishikata, Yazaki, Ohshima, and their co-workers used a copper-catalyzed generation of 2-azaallyl radicals to develop a synthesis of hindered α-amino acid derivatives. 44,45 Given the high demand for tryptamine derivatives in drug discovery and our experience with 2-azaallyl anions as SEDs, we became interested in expanding our ethylamine synthesis strategy to tryptamines (Scheme 1d).…”