Literature Survey for the Synthesis of 2-Aminobiphenyl

Topics: Catalysis, Suzuki reaction, Heck reaction Pages: 6 (1467 words) Published: September 20, 2012
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


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 chlorides and organostannanes. The drawback with organostannanes is that they are extremely toxic and commercially unavailable. The chemical reaction involved is as follows:

Fig 2.2: Stille Coupling Reaction – Aryl chloride (1.0mmol), Organostannane (1.2mmol), 0.5mol% catalyst, CsF (2.0mmol), EtOH/H2O (2.0mL, 1:1), 50°C


Synthesis of 2-Aminobiphenyl using Palladium catalysed ortho-arylation of benzamides by aryl iodides (Dan-Dan Li, Ting-Ting Yuan, and Guan-Wu Wang, 2012 ) This method involves three steps which are briefly outlined below: a. Benzamide (0.5mmol) + Phenyl Iodide (1mmol)  2-Phenyl benzamide

Fig 2.3: Chemistry of conversion of Benzamide to 2-Phenyl benzamide

Conditions:  Pd(OAc)2 (0.025mmol / 5mol%) + 1mmol of Ag2O (additive) in 5mL of Acetic acid Manufacture of 100 TPA of 2-Aminobiphenyl Page 6

Literature Survey    Temp: 120°C Reaction Time: 5hrs Yield: 74%

On a lab scale, this reaction was carried out in a stirred vessel, monitored by thin layer chromatography (TLC) and stopped at the desired time. The solvent was vacuum evaporated to dryness and the residual was separated on a silica gel column with ether/ethyl acetate (2:1) as the eluent. b. 2-Phenyl benzamide (49.3 mg, 0.25 mmol) + solution of KOH (35.3 mg, 0.63 mmol) in MeOH (2.5 mL)  Methyl biphenyl-2-yl carbamate     The reaction mixture was stirred at room temperature until a homogeneous solution was obtained, then cooled to 5−10 °C in an ice−water bath. Diacetoxyiodobenzene (80.9 mg, 0.25 mmol) was added in one portion and dissolved within 5 min. The reaction was stirred at ice-bath temperature for 15 min followed by warming to room temperature while stirring for an additional 45 min. Upon completion of the reaction (TLC monitored), the methanol was removed in vacuo and the reaction mixture was quenched with water and extracted with CH2Cl2 (10 mL × 3).  The solvent was removed in vacuo and the residual was separated on a silica gel column with petroleum...
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