Sulfuric Acid → HCID 67425509, compound

Participants

Reaction Conditions

Reaction Steps

A 12-L 4-neck round bottom flask equipped with a thermocouple, a mechanical stirrer, a condenser, and a nitrogen inlet adapter was charged with Boc-protected intermediate 5 as prepared in the previous step (434 g; 1.08 mol) and methanol (3.5 L) and the solution was stirred at 20° C. under nitrogen. A solution of 9 M H2SO4 (140 mL; 1.26 mol) was added dropwise over 3 min, and then the mixture was warmed to 60° C. and stirred for 6 h. The reaction was cooled to 40° C. and NaHCO3 (420 g; 5.00 mol) was added as one portion and stirred at 12-16° C. for 1 h. The white solid was removed by filtration and washed with MeOH (200 mL×3) and then discarded after being checked by HPLC. The filtrate (total about 4.0 L) was concentrated at 50° C. under high vacuum (20 mmHg) and chased with MeOH (1 L) once to afford crude title compound, 6, as an off-white foamy solid, which was kept at 0° C. in the dark under N2 and used for futher reaction without additional purification. The structure of compound 6 was confirmed by 1H-NMR.

Provenance & Evidence