Suzuki – Coupling Reaction

The palladium-catalyzed cross – coupling reaction between organohalo compounds and orgabo boran compounds under basic conditions furnishes carbon – carbon single bond is called as SUZUKI – COUPLING REACTION.

1. In Suzuki-coupling reaction, the reactants are may be either organohalo compounds or organo triflates and orgabo boran reagents.

2. In organohalocompounds the organic group may be vinyl, aryl.

3. The reactivity order of organo halo compounds (or) triflets towards activated alkenes is as follows,
R – I > R – OTF > R – Br >> R – Cl

4. In Suzuki-coupling reaction, the reactants organo boron reagents are organo boranes, boronic acids (RB (OH)2) and boronate esters (RB (OR’)2). The organic group may be vinyl -, aryl-, alkynyl, 1-alkenyl- and aryl.

5. Treatment of Grignard or lithium reagents with trialkyl borates to produce the corresponding boronate esters which on further hydrolysis furnishes the corresponding boronic acids. However several problems are associated with the preparation of these boron reagents such as purification, polymerization and lack of atom economy.

6. These problems are overcome by converting the boronate esters to potassium organotri-fluoroborates with potassium hydrogen fluoride (KHF2), organotrifluoroborates which are crystalline solids, readily isolated and stable to air and moisture.

7. The Suzuki-coupling reagent: The combination of catalyticall amount of Palladium Pd (0) Pd (II), Base is called as Suzuki-coupling reagent.

8. In Suzuki-coupling reaction, the bases used are such as Sodium carbonate (Na2CO3), Potassium carbonate (Ka2CO3), Hydroxide, Alkoxide- NaOMe etc.

9. Role of the Base:

10. In Suzuki-coupling reaction, the solvents used are solvents like DMF (dimethyl formamide), THF, dtethylether, benzene & chloroform etc,

11. In Suzuki-coupling reaction, the products are may be – stereo and region specific conjugated dienes, enynes, aryl substituted alkenes and biaryl compounds.

12. In Suzuki-coupling reaction, stereochemistry is retained i.e. whatever the reactant stereochemistry is passed throughout the product stereochemistry (reactant stereochemistry and product stereochemistry is same).

13. The yield of Suzuki coupling reactions is high when compared to Heck coupling reaction, so coupling reactions is used in industries.