Electrochemical/Photochemical Aminations Based on Oxidative Cross-Coupling between C–H and N–H

Abstract

The construction of nitrogen-containing molecules remains at the cutting edge of organic synthesis because of its wide application in various areas. Instead of prefunctionalized substrates, using free C–H and N–H bonds in the starting materials can supply a more sustainable avenue to the C–N bond-forming reactions. Compared with the well-developed transition-metal-catalyzed protocols, the strategy of introducing optical or electrical energy into reactions is fantastic and appealing. As a result, visible light or electricity mediated amination transformations have continued to develop over the past several years. In this short review, recent progress of carbon–nitrogen bond-forming reactions based on the oxidative cross coupling between C(sp2, sp3)–H and N–H are summarized.1 Introduction2 C(sp2)–H/N–H Oxidative Cross Coupling2.1 Aryl C(sp2)–H as C Nucleophiles2.1.1 Azoles as N Nucleophiles2.1.2 Sulfonamides or Sulfonimides as N Nucleophiles2.1.3 NH3 as N Nucleophile2.1.4 Morpholine as N Nucleophile2.1.5 Diaryl Amines as N Nucleophiles2.1.6 Primary Amines as N Nucleophiles2.1.7 Imides as N Nucleophiles2.1.8 Imines as N Nucleophiles2.2 Alkenyl C(sp2)–H as C Nucleophiles2.3 Aldehydic C(sp2)–H as C Nucleophiles3 C(sp3)–H/N–H Oxidative Cross Coupling3.1 Benzylic C(sp3)–H as C Nucleophiles3.2 α-C(sp3)–H as C Nucleophiles4 Conclusions and Outlook

High Electric Field on Water Microdroplets Catalyzes Spontaneous and Ultrafast Oxidative C–H/N–H Cross-Coupling

“…However, either stoichiometric strong oxidizers or high temperatures are needed to trigger the reactions, hampering the incorporation of vulnerable functional groups into the substrates and triggering unwanted side reactions. In view of this, photo-induced and electrochemical oxidative C–H/N–H coupling − under mild conditions has received increasing attention, which have significantly diversified the substrates. Mechanistically, these reactions are initiated by electrochemically or photocatalytically removing an electron from the substrates, followed by C/N cross-coupling and hydrogen evolution. , Nevertheless, transition metal catalysts are still needed in some of these cases, and at least a light source or an electrochemical cell is involved as a means to oxidize the substrates.…”

Electrochemical Deoxygenative Thiolation of Preactivated Alcohols and Ketones

“…Electrochemically initiated radical reactions have demonstrated great redox efficiency, innate scalability, and sustainability owing to the characteristic electrolytic processes . Transition-metal-catalyzed electro-coupling has been applied for C–C, C–O, C–N, and C–S bond formation for great kinetic control of radical reactivity and compatibility. Our group reported alkyl carbazates for anodic deoxygenative functionalization of heteroarenes.…”

Copper catalyzed late-stage C(sp3)-H functionalization of nitrogen heterocycles

“…Direct C(sp 3 )-H bond functionalization of N-heterocycles represents an attractive topic and is of paramount importance to drug development [3][4][5][6][7][8][9] . A number of approaches on C-H bond alkylation of N-heterocycle have been developed so far, e.g., C-H oxidation to iminium intermediate [6][7][8][10][11][12][13] , lithiation of α-position, C(sp 3 )-H bond activation [14][15][16][17] , photoredox-based approaches, etc [18][19][20][21][22][23][24] . In particular, cross-dehydrogenative coupling (CDC), which proceeds via C-H oxidation to iminium intermediate, developed by Li 25,26 based on the oxidative activation of C(sp 3 )-H bonds of amines and ethers has been intensively studied (Fig.…”