反应详情

Dimethylsulfoxide (2.2 ml, 31 mmol) was slowly added via syringe to a stirred −78° C. solution of oxalyl chloride (15 ml, 171 mmol) in methylene chloride (35 ml) under inert atmosphere. After 10 min., a solution of N-p-toluoyl valinol (6.0 g, 29 mmol) in methylene chloride (50 ml) was added and the stirring was continued for additional 15 min. Triethylamine was added (6 ml, 389 mmol) and the reaction was allowed to warm to ambient temperature. After 1.5 h, the reaction was diluted with 50% ethyl acetate in hexanes and washed with water and brine. Filtration through a pad of silica gel and subsequent solvent removal left a solid residue. Chromatography eluting with 20% ethyl acetate in hexanes, then 33% ethyl acetate in hexanes gave N-p-toluoyl valinaldehyde (3.6 g) as a solid, which was utilized in Step 6.

1. waitthe stirring was continued for additional 15 min
2. waitAfter 1.5 h
3. washwashed with water and brine
4. filtrationFiltration
5. customthrough a pad of silica gel and subsequent solvent removal
6. waitleft a solid residue
7. washChromatography eluting with 20% ethyl acetate in hexanes