Triethylamine → 2-[[(1,1-Dimethylethoxy)carbonyl]amino]ethyl 2,4,6-trimethylbenzenesulfonate

Participants

Reaction Conditions

Reaction Steps

Triethylamine (65 mL, 465.3 mmole, 1.5 eq) was added in one portion to a solution of tert-butyl N-(2-hydroxyethyl)carbamate (50.11 g, 310.2 mmole, 1.0 eq.) in dichloromethane (250 mL, 5 vols). The solution was cooled to −10° C. and trimethylamine hydrochloride (14.84 g, 155.1 mmole, 0.5 eq.) was added in one portion. The resultant mixture was cooled further to −15° C., stirred for 5 minutes, then treated with a solution of mesitylenesulfonyl chloride (74.74 g, 341.2 mmole, 1.1 eq) in dichloromethane (250 mL, 5 vols), over 28 minutes such that the internal temperature remained below −10° C. Once the addition was complete a precipitate had formed and the mixture was stirred at −10° C. for a further 30 minutes. Water (400 mL, 8 vols) was added and all of the precipitate dissolved. The mixture was stirred rapidly for 5 minutes, and then the two layers were separated. A solvent swap from dichloromethane to isopropanol was carried out by distillation at reduced pressure. Solvent was removed (450 mL) and replaced with iso-propanol (450 mL (initial pressure was 450 mbar, b.p. 24° C.; final pressure was 110 mbar, b.p. 36° C.). At the end of the distillation, solvent (150 mL) was removed to bring the volume down to 350 mL (7 vols with respect to the amount of tert-butyl N-(2-hydroxyethyl)carbamate used). The solution was cooled to 25° C., then water (175 mL) was added slowly with stirring, causing the solution gradually to turn cloudy. No solid had precipitated at this stage. More water (125 mL) was added, and a solid precipitate started to form after about 75 mL had been added. The internal temperature rose from 25° C. to 31° C. The mixture was stirred slowly and cooled to 7° C. The solid was collected by filtration, washed with iso-propanol:water (1:1, 150 mL) and dried in vacuo at 40° C. for 21 hours to give the sub-title compound as a white crystalline solid (92.54 g, 87%).

Provenance & Evidence