tert-butyl 1-tosyl-1H-pyrrole-3-carboxylate → tert-butyl 2-((R)-1-((S)-1,1-dimethylethylsulfinamido)ethyl)-1-tosyl-1H-pyrrole-3-carboxylate

Participants

Reaction Steps

To a solution of tert-butyl 1-tosyl-1H-pyrrole-3-carboxylate (,287a 1.67 g, 5.20 mmol) in 40 mL of THF at −78° C. was added LDA(Aldrich) (1.7 M solution in heptane/THF/ethylbenzene, 3.67 mL, 6.24 mmol) slowly dropwise. After 45 min, a solution of (S,E)-N-ethylidene-2-methylpropane-2-sulfinamide (Prepared according to PCT Int. Appl., WO2005103020; 0.765 g, 5.20 mmol) in THF was added slowly dropwise via syringe over several min. After 15 min, the acetone/dry ice bath was removed and the reaction was quenched by dropwise addition of saturated aq. NH4Cl and Et2O. The organic layer was washed with saturated aq. NH4Cl once, saturated aq. NaCl once and the organics were dried over anhydrous MgSO4, filtered, and concentrated in vacuo. The material was treated with DCM and purified by silica gel chromatography (80 g ISCO redisep gold column) using 0-50% EtOAc/hexanes. The product-containing fractions were concentrated to afford tert-butyl 2-((R)-1-((S)-1,1-dimethylethylsulfinamido)ethyl)-1-tosyl-1H-pyrrole-3-carboxylate (287b; 1.05 g, 2.24 mmol, 43% yield) as a white solid. 1H NMR (400 MHz, CDCl3) δ ppm 7.73 (2H, d, J=8.2 Hz), 7.28-7.34 (3H, m), 6.58 (1H, d, J=3.3 Hz), 5.95 (1H, d, J=9.2 Hz), 5.14 (1H, br. s.), 2.43 (3H, s), 1.50-1.54 (12H, m), 0.96 (9H, s). m/z (ESI, +ve) 469.1 (MA-1)11.

Provenance & Evidence