Reaction #1867

Reaction equation

trans- 7-chloro-5-(2-chlorophenyl)-1-isobutyl-2-oxo-1,2,3,5-tetrahydro-4,1-benzoxazepine-3-acetic acid

pivaloyloxymethyl chloride

N,N-diisobutyl ethylamine

water

→

trans-7-chloro-5-(2-chlorophenyl)-1-isobutyl-2-oxo-1,2,3,5-tetrahydro-4,1-benzoxazepine-3-acetic acid pivaloyloxymethyl ester

Solvents

N,N-dimethylformamide

ethyl acetate

Conditions

Workup

1. 1
   Extractionfollowed by extraction
2. 2
   WashThe ethyl acetate layer was washed with an aqueous solution of potassium hydrogensulfate
3. 3
   Dryingan aqueous solution of sodium hydrogencarbonate and water, successively, which was dried over anhydrous magnesium sulfate
4. 4
   workup.DISTILLATIONThe solvent was then distilled off under reduced pressure
5. 5
   OtherThe residue was purified by means of a silica gel column chromatography (hexane:ethyl acetate=10:1 to 5:1)

Procedure

In N,N-dimethylformamide (10 ml) was dissolved trans- 7-chloro-5-(2-chlorophenyl)-1-isobutyl-2-oxo-1,2,3,5-tetrahydro-4,1-benzoxazepine-3-acetic acid (0.5 g) obtained in Example 2. To the solution were added pivaloyloxymethyl chloride (0.43 ml), N,N-diisobutyl ethylamine (0.52 ml) and KI (0.2 g). The mixture was stirred at room temperature overnight. To the reaction mixture were added water (100 ml) and ethyl acetate (100 ml), followed by extraction. The ethyl acetate layer was washed with an aqueous solution of potassium hydrogensulfate, an aqueous solution of sodium hydrogencarbonate and water, successively, which was dried over anhydrous magnesium sulfate. The solvent was then distilled off under reduced pressure. The residue was purified by means of a silica gel column chromatography (hexane:ethyl acetate=10:1 to 5:1) to afford trans-7-chloro-5-(2-chlorophenyl)-1-isobutyl-2-oxo-1,2,3,5-tetrahydro-4,1-benzoxazepine-3-acetic acid pivaloyloxymethyl ester (0.55 g).

Source