Literature Survey for the Synthesis of 2-Aminobiphenyl
Literature Survey 2. Literature Survey Literature survey indicated 135 possible routes for the synthesis of 2-Aminobiphenyl. It must be noted that all routes available were lab-scale and no patents for the desired compound were available. Also, majority of these synthesis routes gave extremely low yields of our desired product and produced a number of other by-products in higher yields. Therefore, only the pathways giving significant yields of the desired product have been listed below. i. Suzuki Coupling of aryl chlorides with aryl boronic acids (Myung-Jong Jin and Dong-Hwan Lee, 2010) Suzuki coupling reaction is an example of heterogeneous catalysis. The advantage of heterogeneous catalytic systems is that they can be considerably re-used whilst keeping the inherent activity of the catalytic centre. Aryl bromides and iodides are widely employed in heterogeneous coupling reactions. But from a practical point of view, the use of aryl chlorides is highly preferable because they are readily available and inexpensive. The catalyst used was a triethoxysilyl-functionalized palladium complex immobilized on the surface of magnetite Fe3O4 coated with silica. The significant advantage of this catalyst is retained activity over a number of runs and magnetic recyclability. However catalyst preparation is complex and involves microwave heating and thus cannot be applied industrially. Suzuki couplings are usually carried out in organic solvents or aqueous organic mixed solvents. The chemical reaction involved is as follows:
Fig 2.1: Suzuki Coupling Reaction – Aryl chloride (1.0mmol), Aryl boronic acid (1.2mmol), 0.5mol% catalyst, K2CO3 (2.0mmol), Tetrabutyl ammonium bromide (0.5mmol), 60°C Manufacture of 100 TPA of 2-Aminobiphenyl
Page 5
Literature Survey
ii.
Stille Coupling of aryl chlorides with organostannanes (Myung-Jong Jin and Dong-Hwan Lee, 2010) Stille Coupling is similar to Suzuki Coupling in terms of the catalyst used. The raw materials involved are aryl
Fig 2.1: Suzuki Coupling Reaction – Aryl chloride (1.0mmol), Aryl boronic acid (1.2mmol), 0.5mol% catalyst, K2CO3 (2.0mmol), Tetrabutyl ammonium bromide (0.5mmol), 60°C Manufacture of 100 TPA of 2-Aminobiphenyl
Page 5
Literature Survey
ii.
Stille Coupling of aryl chlorides with organostannanes (Myung-Jong Jin and Dong-Hwan Lee, 2010) Stille Coupling is similar to Suzuki Coupling in terms of the catalyst used. The raw materials involved are aryl