Copper‐Catalyzed Deoxygenative C‐2 Amination of Quinoline N‐Oxides

Abstract

An unprecedented reaction between quinoline N‐oxides with O‐benzoylhydroxylamines was developed by using CuCl as catalyst, generating deoxygenative products of 2‐aminoquinolines in good yields. 1,2‐Dichloroethane (DCE) as solvent was also served as reducing agent to cleave the N–O bond with no additional reductant needed in the reaction.

Catalytic N‐Acylation of Cyclic Amines by Arylglyoxylic Acids via Radical‐Radical Cross‐Coupling

“…[12] While the initial Cu(II) to Cu(I) transition might be due to SET from 1a, the transition of Cu(I) to Cu(II) to complete the catalytic cycle is conceivably attributed to a second SET, promoted by the NÀ O bond cleavage of 4e. [13] Our proposed mechanism, as depicted in Scheme 4, is in accord with these experimental findings and literature [3a,7b,13] In a catalytic cycle, the Cu(II) catalyst is initially reduced to Cu(I) species via a SET from 1. In the presence of 4, the resulting Cu(I) species forms Cu(II) catalyst, thereby generating amine radicals that undergo decarboxylative Nacylation with arylglyoxylate radicals via radical-radical crosscoupling to produce 5.…”

Recent Advances in the Synthesis of C2‐Functionalized Pyridines and Quinolines Using N‐Oxide Chemistry

“…[40] Deoxygenative amination through metal catalysis is also reported (Scheme 21). [41] Notably, DCE serves as both the solvent and reductant in this transformation. O-benzoyl hydroxylamine 73 was reduced by Cu + to generate an aminyl radical, which reacted with 19 to produce intermediate 74.…”

Clean Preparation of Quinolin-2-yl Substituted Ureas in Water

“…According to previous reports, the C2 position of quinoline N -oxides may be functionalized via a number of reaction processes, which include the C–H bond alkylation, − arylation, alkenylation, − acetoxylation, , sulfonylation, − amidation, − amination, − hydroxylation, , phosphonation, , and thiolation of quinoline N -oxides. However, to the best of our knowledge, the preparation of quinolin-2-yl substituted ureas from readily available quinoline N -oxides has never been reported.…”