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In organic chemistry, a cross-coupling reaction is a reaction where two different fragments are joined. Cross-couplings are a subset of the more general coupling reactions. Often cross-coupling reactions require metal catalysts. One important reaction type is this:
This recognition sparked interest in polymerization mechanism so that it could be expanded to other monomers. Few polymers can be synthesized via CTP, so most conjugated polymers are synthesized via step-growth using palladium catalyzed cross-coupling reactions.
In one important reaction type, a main group organometallic compound of the type R-M (where R = organic group, M = main group centre metal atom) reacts with an organic halide of the type R'-X with formation of a new carbon-carbon bond in the product R-R'. The most common type of coupling reaction is the cross coupling reaction. [1] [2] [3]
These coupling reactions are made possible by modifying the backbone chemically. [10] Common reaction mechanisms used to synthesize these copolymers include free- radical polymerization , anionic polymerization , atom-transfer radical-polymerization , and living polymerization techniques.
The coupling of a terminal alkyne and an aromatic ring is the pivotal reaction when talking about applications of the copper-promoted or copper-free Sonogashira reaction. The list of cases where the typical Sonogashira reaction using aryl halides has been employed is large, and choosing illustrative examples is difficult.
Key step in synthesis of lithospermic acid. The total synthesis of calothrixin A and B features an intramolecular Pd-catalyzed cross coupling reaction via C-H activation, an example of a guided C-H activation. Cross coupling occurs between aryl C-I and C-H bonds to form a C-C bond. [31]
One of the key characteristics of a living polymerization is that the chain termination and transfer reactions are essentially eliminated from the four elementary reactions of chain-growth polymerization leaving only initiation and (chain) propagation reactions. A key characteristic of living polymerization is that the rate of initiation ...
Building blocks that make up the network of CMPs must contain an aromatic system and have at least two reactive groups. To generate the porous structure of CMPs, cross-coupling of building blocks with different geometries to create a 3-D polymer backbone is necessary, while self-condensation reactions occur in the homo-coupling of building blocks with similar geometry. [2]