Surface-Controlled Mono/Diselective ortho C–H Bond Activation

Abstract

One of the most charming and challenging topics in organic chemistry is the selective C-H bond activation. The difficulty arises not only from the relatively large bond-dissociation enthalpy, but also from the poor reaction selectivity. In this work, Au(111) and Ag(111) surfaces were used to address ortho C-H functionalization and ortho-ortho couplings of phenol derivatives. More importantly, the competition between dehydrogenation and deoxygenation drove the diversity of reaction pathways of phenols on surfaces, that is, diselective ortho C-H bond activation on Au(111) surfaces and monoselective ortho C-H bond activation on Ag(111) surfaces. The mechanism of this unprecedented phenomenon was extensively explored by scanning tunneling microscopy, density function theory, and X-ray photoelectron spectroscopy. Our findings provide new pathways for surface-assisted organic synthesis via the mono/diselective C-H bond activation.

Recent Progress in the Fabrication of Low Dimensional Nanostructures via Surface-Assisted Transforming and Coupling

“…Another type of C-C bond formed reaction is consequently dehydrogenation reactions without polycyclic aromatic hydrocarbon obtained. In Figure 2(b) [9], the possible process taking place on Ag(111) is 1,3,5-tris(4-hydroxyphenyl) benzene (THPB) getting dehydrogenated into oligomers, and STM image confirmed the temperature-induced successive phase evolution from longrange ordered self-assembly structure to a thermally triggered surface chemical reaction, and the ordered structure of THPB monomers disappeared. However, the activation on C-H bond is at the same special site, ortho-C-H-bonds, leading to the ortho-ortho-coupling of THPB after annealing.…”

“…The deformation of polymers results from dehydrogenation reaction taking place at relatively different site of carbon seriously influencing their physical properties, but also polymers with irregular orientation confined on the surface would hinder the formation of long-range ordered polymers. Hence, there is inevitable requiring on exploration of the mechanism of surface-controlled selective C-H bond activation in order to successfully direct experimental fabrication [9].…”

Thermodynamics of an Electrocyclic Ring-Closure Reaction on Au(111)

“…11,[15][16][17][18][19][20][21][22][23] These studies have almost exclusively been performed at 0 K, excluding even zero-point vibrations, and only a few examples have attempted to include temperature effects. 11,20 In particular, no studies have addressed the thermodynamics of reactions related to on-surface synthesis.…”

A Shape-Persistent Polyphenylene Spoked Wheel

“…5 With the combination of sp-, sp 2 -, and sp 3 -hybridized carbon atoms, a number of 2D carbon materials with different architectures have also been synthesized and/or theoretically predicted. 2,[6][7][8][9][10][11][12][13][14][15][16][17][18] In particular, graphene has attracted major attention during the last decade, which also stimulated the studies of other 2D carbon materials such as γ-graphyne and graphdiyne ( Figure 1). 10,11,14,19,20 Atomically precise syntheses of γ-graphyne and graphdiyne remain elusive, but widely studied phenylene-ethynylene-based macrocycles can be regarded as their molecular subunits.…”

“…Nevertheless, the number of reported examples of 2D carbon materials is still limited. 2,[6][7][8][9][10][11][12][13][14][15][16][17][18] By replacing ethynylene groups of γ-graphyne and graphdiyne with p-phenylene units, two purely sp 2 -hybridized 2D carbon structures with hexagonal symmetry can be conceived, which we name graphenylene-1 and graphenylene-2, respectively ( Figure 1). Notably, graphenylene-1 corresponds to a single-layer substructure of the hypothetical carbon allotrope "cubic graphite", 26 the synthesis of which still remains elusive.…”