Tin‐Free Radical Carbonylation: Synthesis of Acylated Oxime Ethers Using Alkyl Allyl Sulfone Precursors, Carbon Monoxide, and Phenylsulfonyl Oxime Ether

Abstract

Acylated oxime ethers have been prepared by a three-component coupling reaction using alkyl allyl sulfone precursors, carbon monoxide, and phenylsulfonyl oxime ether derivatives under tin-free radical reaction conditions.

Transition‐Metal‐Free Alkoxycarbonylation of Aryl Halides

“…These results usually involve a xenon photolytic system or AIBN/tin hydride mediated radicalchain reaction employing alkyl iodides as substrates. [24][25][26][27][28][29][30] To the best of our knowledge, there is no example of employing a transition-metal-free process in alkoxycarbonylation of aryl halides. Herein, we disclose a protocol for accessing tert-butyl benzoates through the transition-metal-free alkoxycarbonylation of aryl halides.Our experiment was initiated by treating 4-iodotoluene (1 a) with KOtBu in the presence of a high pressure CO (Table 1).…”

Radicals in organic synthesis. Part 1

“…A range of allyl sulfones, such as 448, undergo a three-component coupling reaction with carbon monoxide and phenylsulfonyl oxime ether derivatives such as 330a,b to give 449a,b (Scheme 139). 290 Primary halides invariably furnish the desired carbonylated product, but secondary halides are more problematic; the stability of secondary radicals means that the carbonylation step is inefficient and direct addition to the oxime ether becomes a competitive side reaction. This can be overcome by increasing the pressure of carbon monoxide or by the use of oxime ether 330b; it appears that 330b is more reactive towards acyl radicals than 330a and, thus, traps the carbonylated intermediate more effectively.…”

Transition‐Metal‐Free Alkoxycarbonylation of Aryl Halides

“…Generally, low-valent-metal catalysts such as palladium(0) are required to activate the CÀX bond, whereas the strong binding ability of CO towards low-valent metals deactivate the catalyst, which present a challenge in this transformation. [24][25][26][27][28][29][30] To the best of our knowledge, there is no example of employing a transition-metal-free process in alkoxycarbonylation of aryl halides. The key challenge of this idea is to determine how to activate CÀX without the help of transition-metal catalysts.…”

“…The key challenge of this idea is to determine how to activate CÀX without the help of transition-metal catalysts. [24][25][26][27][28][29][30] To the best of our knowledge, there is no example of employing a transition-metal-free process in alkoxycarbonylation of aryl halides. Recently, transition-metal-free coupling reactions of aryl halides with arenes and alkenes have been developed, and the combination of MOtBu and bidentate nitrogen ligands was employed to initiate the aryl radical by single-electron transfer (SET).…”