A Pd‐Catalyzed Three‐Component Reaction and Hydrogenation Strategy to Prepare 2‐Functionalized Cyclic Ethers Involving a Radical Initiating C(sp³)‐H Activation

Abstract

A Pd‐catalyzed three‐component reaction and hydrogenation strategy to prepare a series of 2‐functionalized cyclic ethers with high to excellent yields was established. A plausible reaction mechanism for the three‐component coupling of N‐tosylhydrazones, aryl halides and cyclic ethers was proposed, which involves a radical initiating α‐C(sp3)‐H activation of the ethers and addition at β‐position of the palladium carbene‐derived α‐substituted styrenes. The resulting free radicals would undergo a disproportionation reaction to afford 2‐(2′,2′‐diarylvinyl)ethers and 2‐(2′,2′‐diarylethyl)ethers. The latter could also be formed from the oxidation of the free radicals via benzylic cations.

Recent Advances in Transition‐Metal‐Catalyzed Reactions of N‐Tosylhydrazones

“…[110] Very recently, the group of Luo reported a novel palladium-catalyzed three-component reaction and hydrogenation strategy to prepare 2-functionalized cyclic ethers (Scheme 88). [111] This reaction incorporates N-tosylhydrazone chemistry in a partial radical process. This reaction involves an interesting pathway via radical initiated α-C(sp 3 )À H activation of ethers and addition at the β-position of the palladium carbene-derived α-substituted styrenes.…”