Auxiliary-directed etherification of sp² C–H bonds under heterogeneous metal–organic framework catalysis: synthesis of ethenzamide

Abstract

An efficient protocol for 8-aminoquinoline assisted alkoxylation and phenoxylation of sp2 C–H bonds under heterogeneous catalysis was developed.

Silver-Mediated Methoxylation of Aryl C(sp2)–H Bonds Directing by DMEDA

“…While MgSO 4 were used as an additive, the yield was improved to 78% (Entry 14, Isolated yield 71%). However, no obvious improvement could be observed when other additives were added to this system (Entry [15][16][17][18][19]. This may due to the high binding energy of Ag(3d 5/2 ) states for AgSO 4 , a Ag(II) compuond [39].…”

“…Compared to the traditional method for carbon-oxygen bond coupling [3][4][5][6], transition metal catalyzed C-H alkoxylation with alcohols has received much attention in recent decades in terms of atom and step economy [7][8][9][10]. However, direct C-H bond alkoxylation has been mostly limited to a palladium- [11][12][13][14][15] or copper-catalyzed system [16][17][18][19][20] which are both more biological toxicity metals. Recently, the first-row transition metals such as iron, cobalt, and nickel for C-H alkoxylation, have attracted more attention owing to low biological toxicity as well as low cost [21][22][23][24][25].…”

3d Transition Metals for C–H Activation

“…Recently, Truong and coworkers achieved the etherification of quinolinamides 278 under metal-organic framework-enabled heterogeneous catalysis (Scheme 747). 1834 Here, Cu-MOF-74 was employed as the catalyst under an oxygen atmosphere. Leaching experiments substantiated the reaction heterogenity, and the catalyst was reused at least eight times without significant loss of its activity.…”

Copper-Catalyzed Direct C(sp3)–H Alkoxylation to Access Quaternary α-Alkoxylated Amino Acid Derivatives

“…Transition-metal-catalyzed alkoxylation has attracted increasing interest as an efficient synthetic tool to access natural products and other complex biological compounds. − In recent years, first-row transition-metal-catalyzed C–H alkoxylation has been developed . Especially, copper salt, as a powerful and inexpensive catalyst, has attracted more attention in the application of aryl C­(sp 2 )–H alkoxylation, but C­(sp 3 )–H alkoxylation remains a challenge . For α-amino acids, functionalization at the α-position seems to be difficult due to the influence of steric hindrance.…”

“…A completely racemic product was obtained when a chiral α-amino amide was employed, which implied that the enolate intermediate might be involved in this reaction . In a single-electron-transfer (SET) oxidative process, the methoxy radical generated from the fragmentation of AgOMe is transferred to the Cu II -species IV to give the Cu III -intermediate V . Subsequent H -atom transfer gives the Cu III -intermediate VI , which explains why the reaction does not proceed with an N -methylated amide substrate.…”