反应详情

To a solution of 2-ethyl 2-amino-1-(2,4,6-trimethylphenyl)indolizine-3-carboxylate (19.2 g; 59.6 mmol) in 2,2-dimethoxypropane (100 mL), add dl-camphorsulfonic acid (0.2 g). Stir the mixture at reflux for 30 min and then distill slowly to remove ca. 60 mL of volatiles over a 30-minute period. Cool the solution to ambient temperature under inert atmosphere, dilute with anhydrous toluene (50 mL), and concentrate in vacuo. Dissolve the residue in toluene (50 mL) and add dropwise over a 1-hour period a 0.5 M solution of potassium bis(trimethylsilyl)amide in toluene (250 mL; 125 mmol) to the stirred solution. After the addition, stir the mixture for 2 h at ambient temperature, concentrate in vacuo to a small volume and dilute with aqueous NH4Cl. Filter the resulting biphasic mixture and wash successively with water, MeOH), and Et2O. Dry under vacuum to obtain the title compound as a pale yellow solid.

1. temperatureat reflux for 30 min
2. distillationdistill slowly
3. customto remove ca. 60 mL of volatiles over a 30-minute period
4. additiondilute with anhydrous toluene (50 mL)
5. concentrationconcentrate in vacuo
6. dissolutionDissolve the residue in toluene (50 mL)
7. additionAfter the addition
8. stirringstir the mixture for 2 h at ambient temperature
9. concentrationconcentrate in vacuo to a small volume
10. additiondilute with aqueous NH4Cl
11. filtrationFilter the resulting biphasic mixture
12. washwash successively with water, MeOH), and Et2O
13. customDry under vacuum