1) Esterification of trans-Cinnamic Acid

SyntheticPage 504
Published Sep 05, 2011


Reaction Scheme

Procedure

To a 250 mL round bottom flask was added the trans-cinnamic acid, (37,04 g, 0.25 mol, 1 equiv.),  absolute ethanol1 (51.75 g, 1.125 mol, 4.5 equiv.) and benzene (50 mL, 5 M in trans-cinnamic acid ). The flask was equipped with a stirbar, a soxhlet with cellulose membrane insert (containing 25 g of MgSO4), and a reflux condenser. The flask was heated to ≈ 40 oC in oil bath and concentrated H2SO4 (2.56 mL, 0.0475mol, 0.19 equiv.) was added all at once via a syringe. The solution was heated to reflux (oil bath at 120 oC and allowed to stir overnight. The solution was then diluted with ether (≈100 mL). The mixture was transferred to a separatory funnel and washed with 3 X 100 mL of a 10% w.t. sodium bicarbonate solution (CAUTION: CO2 gas is evolved). The organic layer was then washed with deionized water (≈100 mL), brine (≈100 mL), and dried with Na2SO4. The solvent was removed in vacuo by rotary evaporation to afford ethyl cinnamate as a clear yellow oil (38.49 g, 87%)2.

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2) Reduction of cinnamic acid with water-sodium borohydride-Raney nickel

SyntheticPage 521
Published Jan 11, 2012


Reaction Scheme

Procedure

In a 5 L four necked round bottom flask equipped with a mechanical stirrer, 250 mL dropping funnel, thermometer and inlet port open to the atmosphere on a water bath wascharged with 2250 mL of distilled water. Stirring was started and the following reagents added in the order indicated through a funnel: sodium hydroxide (81 g, 2.026 mol, 1.2 equiv), cinnamic acid (250 g, 1.689 mol, 1 equiv), slurry containing activated W-6 Raney nickel (25 g wet) in distilled water. This was stirred for 15 min. Sodium borohydride solution (17.89 g, 0.472 mol, 0.28 equiv, in 1% aqueous  NaOH solution 100 mL)  was added dropwise through dropping funnel over a period of 45 min. The reaction mixture was stirred for additional 30 min at 40-45 oC. TLC analysis revealed that reaction was complete. The reaction flask was removed from the water bath, and the mixture cooled to a room temperature. Then solution was filtered through a Buchner funnel fitted with 2 L. filtration flask under vacuum and the W-6 Raney nickel in the flask rinsed with distilled water (200 mL). The cooled filtrate and washings were poured slowly with mechanical stirring into ice cold concentrated hydrochloric acid (250 mL) in a open 5 L flask . The resulting white colored solid precipitate was collected by Buchner filtration under vacuum, washed with distilled water (250 mL) and air dried to give 245.4 g (96.9 %) of 3-phenyl propionic acid .

 

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