Synthesis
The general procedure for the synthesis of tert-butyl (1,1-dimethyl-2-oxoethyl)carbamate from 2-(Boc-amino)-2-methyl-1-propanol is as follows:
1. To a reaction flask was added a mixture of 56.78 g of dichloromethane and 525 ml of saturated aqueous sodium bicarbonate followed by tert-butyl (2-hydroxy-1,1-dimethylethyl)carbamate (300 mmol) obtained in Reference Example (3a).
2. 0.94 g of tetramethylpiperidine N-oxide (6.0 mmol) and 3.57 g of potassium bromide (30 mmol) were added to the above mixture.
3. the reaction mixture was cooled in an ice bath and stirred at the same temperature for 30 min.
4. 534 ml of 5% aqueous sodium hypochlorite (360 mmol) was slowly added under the cooling conditions of the ice bath and the addition process was controlled to be completed within 1.5 hours.
5. After addition, continue to stir the reaction mixture in the ice bath for 20 minutes.
6. Saturated aqueous sodium thiosulfate solution was added to the reaction mixture to quench the reaction, and then the mixture was returned to room temperature.
7. The reaction mixture was extracted with dichloromethane and the organic layers were combined.
8. The organic layer was washed with brine and subsequently dried with anhydrous magnesium sulfate.
9. The desiccant was removed by filtration and the solvent was evaporated under reduced pressure to give the crude product.
10. Hexane was added to the crude product and the solid was collected by filtration to give 42.32 g of the target compound in 79% yield.
The product was a colorless solid with 1H NMR (CDCl3, 400 MHz) δ: 9.43 (s, 1H), 4.97 (br s, 1H), 1.44 (s, 9H), 1.33 (s, 6H).
References
[1] Chemical and Pharmaceutical Bulletin, 1996, vol. 44, # 11, p. 2061 - 2069
[2] Patent: EP2036896, 2009, A1. Location in patent: Page/Page column 149
[3] Patent: US2003/232832, 2003, A1
[4] Patent: WO2003/99286, 2003, A1. Location in patent: Page 97
[5] Bioorganic and Medicinal Chemistry Letters, 1996, vol. 6, # 24, p. 3051 - 3056
