反应详情

3-Methyl-cyclobutane-1,1-dicarboxylic acid ethyl ester (V. Prelog et al., Helv. Chim. Acta 65 (1982), 2622-2644; 200 mg, 1.074 mmol) was suspended in acetone (20 ml) and stirred in an ice bath. Triethylamine (152 mg, 1.50 mmol) and isobutyl chloroformate (191 mg, 1.40 mmol) were added, the mixture was stirred at 0° C. for min, then sodium azide (129 mg, 1.99 mmol) as solution in water (10 ml) was added, and stirring was continued for 15 min. Then diethyl ether (50 ml) was added, the phases were separated. The organic layer was washed with water, dried over sodium sulfate, filtered and added to refluxing toluene in a flask with distillation bridge. The toluene solution was refluxed for 4 h, the volatiles were evaporated in vacuo, the residue was dissolved in dioxane, 2 N hydrochloric acid was added in excess, and the mixture was stirred until the isocyanate was completely decomposed (approximately 20 min). The volatiles were evaporated and the obtained amino acid ester hydrochloride was used without further purification.

1. stirringthe mixture was stirred at 0° C. for min
2. stirringstirring
3. customthe phases were separated
4. washThe organic layer was washed with water
5. dry with materialdried over sodium sulfate
6. filtrationfiltered
7. additionadded
8. temperatureto refluxing toluene in a flask
9. distillationwith distillation bridge
10. temperatureThe toluene solution was refluxed for 4 h
11. customthe volatiles were evaporated in vacuo
12. dissolutionthe residue was dissolved in dioxane
13. addition2 N hydrochloric acid was added in excess, and the mixture
14. stirringwas stirred until the isocyanate
15. custom(approximately 20 min)
16. customThe volatiles were evaporated
17. customthe obtained amino acid ester hydrochloride was used without further purification