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TCI Practical Example: The Z-Preferential Horner-Wadsworth-Emmons Reaction Using Ethyl Di-o-tolylphosphonoacetate
We are proud to present the Z-preferential Horner-Wadsworth-Emmons reaction (Ando method) using ethyl di-o-tolylphosphonoacetate and p-Tolualdehyde. This reagent can be used to easily introduce (Z)- α,β-unsaturated esters.
Used Chemicals
Procedure
To a solution of ethyl di-o-tolylphosphonoacetate (523 mg, 1.5 mmol, 1.5 eq.) in dry THF (5 mL) was added sodium hydride (64 mg, 1.6 mmol, 1.6 eq.) at −78 °C and the mixture was stirred for 30 minutes. Then p-tolualdehyde (120 mg, 1.0 mmol) was added to the reaction mixture at −78 °C and stirred 2 hours at same temperature. After the solution was quenched with water (15 mL), it was extracted with ethyl acetate (15 mL x 3) and the organic layer was washed with 2 mol/L HCl aq. (10 mL), sat. NaHCO3 aq. (10 mL), and brine (10 mL), dried over sodium sulfate and filtered. The solvent was removed under reduced pressure and the residue was purified by column chromatography (on silica gel, toluene:diethyl ether = 40:1) to give 1 as a colorless oil (175 mg, 91% yield, E:Z = 1:1.29).
Experimenter's Comments
The reaction mixture was monitored by UPLC.
The ratio of E form and Z form was estimated from 1H-NMR.Analytical Data
Compound 1
1H NMR (400 MHz, CDCl3);
1-Z: δ 7.52 (d, J = 8.4 Hz, 2H), 7.16 (d, J = 8.0 Hz, 2H), 6.90 (d, J = 12.8 Hz, 1H), 5.89 (d, J = 12.8 Hz, 1H), 4.19 (q, J = 7.2 Hz, 2H), 2.36 (s, 3H), 1.26 (t, J = 7.2 Hz, 3H).
1-E: δ 7.62 (d, J = 16 Hz, 2H), 7.43 (d, J = 8.0 Hz, 2H), 7.19 (d, J = 8.0 Hz, 1H), 6.40 (d, J = 16.0 Hz, 1H), 4.26 (q, J = 6.8 Hz, 2H), 2.37 (s, 3H), 1.34 (t, J = 6.8 Hz, 3H).
Lead Reference
- Highly Selective Synthesis of Z-Unsaturated Esters by Using New Horner−Emmons Reagents, Ethyl (Diarylphosphono)acetates
