2. Effect of n-Butyllithium on Crisaborole Formation .
| Process
Parameter |
Area % in HPLC |
||||
|---|---|---|---|---|---|
| Equivalents of n-Butyllithium | 10 | 13 | 14 | 15 | Crisaborole (6) |
| 1.8 | 0.70 | 10.81 | 1.80 | 2.20 | 82.01 |
| 2.0 | 0.10 | 6.30 | 0.80 | 2.78 | 89.70 |
| 2.5 | 0.10 | 0.02 | 4.38 | 5.97 | 87.53 |
a
All reactions were conducted utilizing 5.0 g (1.0 equiv) of compound 10, with triisopropyl borate at a stoichiometric ratio of 4.0 equiv under cryogenic conditions of −60 °C and a residence time of 1.5 s. The equivalents of n-butyllithium were varied, while 3 M HCl was employed at 7.0 equiv for the cyclization reaction. The analysis of reaction products was performed using HPLC, measuring the area percentage at a wavelength of 210 nm.