Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp3)-H to construct C-C bonds

Abstract

Ether derivatives are widespread as essential building blocks in various drugs, natural products, agrochemicals, and materials. Modern economy requires developing green strategies with improved efficiency and reduction of waste. Due to its atom and step-economy, the cross-dehydrogenative coupling (CDC) reaction has become a major strategy for ether functionalization. This review covers C-H/C-H cross-coupling reactions of ether derivatives with various C-H bond substrates via non-noble metal catalysts (Fe, Cu, Co, Mn, Ni, Zn, Y, Sc, In, Ag). We discuss advances achieved in these CDC reactions and hope to attract interest in developing novel methodologies in this field of organic chemistry.

Keywords: alkylation; cross-dehydrogenation coupling; ether; non-noble metals.

Scheme 1

Research progress of coupling reactions and active compounds containing α-C(sp³)-functionalized ethers.

Scheme 2

Transition-metal-catalyzed CDC pathways.

Scheme 3

CDC of active methylene compounds in the α-C(sp³) position of ethers.

Scheme 4

InCl₃/Cu(OTf)₂/NHPI co-catalyzed CDC reaction.

Scheme 5

CDC of cyclic benzyl ethers with aldehydes.

Scheme 6

Cu-catalyzed CDC of (a) unactivated C(sp³)–H ethers with simple ketones and (b) double C(sp³)−H functionalization reaction of α-aminocarbonyl compounds with 2-alkyl-1,3-dioxolanes.

Scheme 7

Cu-catalyzed CDC of C(sp³)–H/C(sp³)–H bonds.

Scheme 8

Cu-catalyzed synthesis of chiral 2-substituted tetrahydropyrans.

Scheme 9

CDC of thiazole with cyclic ethers.

Scheme 10

Cu(I)-catalyzed oxidative alkenylation of simple ethers.

Scheme 11

Cross-dehydrogenation coupling of isochroman C(sp³)–H bonds with anisole C(sp²)–H bonds.

Scheme 12

Pd(OAc)₂/Cu(OTf)₂-catalyzed arylation of α-C(sp³)–H bonds of ethers.

Scheme 13

Cu-catalyzed C(sp³)–H/C(sp²)–H activation strategies to construct C(sp³)–C(sp²) bonds.

Scheme 14

Cu(I)-catalyzed C(sp²)–H alkylation.

Scheme 15

Cu-catalyzed C(sp³)–H/C(sp)–H activation to construct C(sp³)–C(sp) bonds (H₂BIP: 2,6-bis(benzimidazol-2′-yl)pyridine).

Scheme 16

Fe-catalyzed CDC reaction pathways.

Scheme 17

Fe₂₍CO)₉-catalyzed functionalization of C–H bonds.

Scheme 18

Ligand-promoted Fe-catalyzed CDC reaction of N-methylaniline with ethers.

Scheme 19

Fe-catalyzed CDC of C(sp³)–H/C(sp³)–H bonds.

Scheme 20

Fe-catalyzed hydroalkylation of α,β-unsaturated ketones with ethers.

Scheme 21

Solvent-free Fe(NO₃)₃-catalyzed CDC of C(sp³)–H/C(sp²)–H bonds.

Scheme 22

Alkylation of disulfide compounds to afford tetrasubstituted alkenes.

Scheme 23

Fe-catalyzed formation of 1,1-bis-indolylmethane derivatives.

Scheme 24

Alkylation of coumarins and flavonoids.

Scheme 25

Direct CDC α-arylation of azoles with ethers.

Scheme 26

CDC of terminal alkynes with C(sp³)–H bonds adjacent to oxygen, sulfur or nitrogen atoms.

Scheme 27

Alkylation of terminal alkynes.

Scheme 28

Co-catalyzed functionalization of glycine esters.

Scheme 29

Co-catalyzed construction of C(sp²)–C(sp³) bonds.

Scheme 30

Co-catalyzed CDC of imidazo[1,2-a]pyridines with isochroman.

Scheme 31

Co-catalyzed C–H alkylation of (benz)oxazoles with ethers.

Scheme 32

Cobalt-catalyzed CDC between unactivated C(sp²)–H and C(sp³)–H bonds.

Scheme 33

MnO₂-catalyzed CDC of the inactive C(sp³)-H.

Scheme 34

Oxidative cross-coupling of ethers with enamides.

Scheme 35

Ni(II)-catalyzed CDC of indoles with 1,4-dioxane.

Scheme 36

Chemo- and regioselective ortho- or para-alkylation of pyridines.

Scheme 37

Asymmetric CDC of 3,6-dihydro-2H-pyrans with aldehydes.

Scheme 38

CDC of heterocyclic aromatics with ethers.

Scheme 39

Indium-catalyzed alkylation of DHPs with 1,3-dicarbonyl compounds.

Scheme 40

Rare earth-metal-catalyzed CDC reaction.

Scheme 41

Visible-light-driven CDC of cycloalkanes with benzazoles.

Scheme 42

Photoinduced alkylation of quinoline with cyclic ethers.

Scheme 43

Photocatalyzed CDC reactions between α-C(sp³)–H bonds of ethers and C(sp²)–H bonds of aromatics.