Hydrocarbon is an organic compound composed only of two elements, carbon and hydrogen. As an important fuel and chemical raw material, hydrocarbon and its derivatives often play an irreplaceable role in human production and life, and profoundly improve people's lives. C-H activation is an important and hot area that has been developed most rapidly in recent years. Due to its outstanding advantages and great challenges, the direct functional group reaction of the C-H bond is even called the holy grail of the chemical industry. As shown in figure 1, C-H activation is a chemical reaction in which carbon-hydrogen bonds are cleaved and replaced by carbon-X bonds (where X = carbon, oxygen or nitrogen). Catalysts commonly used in the modification process are transition metals such as Pd, Ru and Rh.
Figure 1. C-H bond activation diagram
C-H activation can be divided into three broad categories depending on the mechanism:
Figure 2. The schematic diagram of methane (CH4) forming methyl hydrogen sulfate in H2SO4
Figure 3. The reaction process of indole and enolate formation of hydrazine-carvone intermediate
The products in the above reactions are commonly used scaffolds for a variety of natural products, including hapalindole Q and ambiguine H. The core structure can be formed by C-H activation via a C-C bond. The intrinsic reactivity of indole and enolates leads to the formation of C-C bonds to form indole-carvone intermediates.
Apart from this, the transition metal catalyzed C-H reaction can also be summarized as follows:
Table 1. The reaction types and reaction formulas of C-H Activation
Phase Transfer Catalysts