Toluene → Methyl (S)-(-)-2-Isocyanato-3-methylbutyrate

Participants

Reaction Steps

A solution of 1.9M phosgene in toluene (9.41 mL, 17.89 mmol) was added to a suspension of H-Val-OCH3.HCl (1.0 g, 5.96 mmol). The reaction mixture was heated at reflux for 2 h under a dry ice condenser, cooled to room temperature, sparged vigorously with nitrogen for 1.5 h and then concentrated to dryness. Toluene (5 mL) was added to the residue and the resulting solution concentrated to dryness to give (S)-2-isocyanato-3-methylbutanoic acid methyl ester. This product was dried under high vacuum for 5 min and then used in the following step. 1H NMR(CDCl3) δ3.95-3.94 (d, J=3.82 Hz, 1H), 3.81 (s, 3H), 2.35-2.22 (m, 1H), 1.04-1.02 (d, J=6.8 Hz, 3H), 0.91-0.89 (d, J=6.74 Hz, 3H).

Provenance & Evidence