Reaction #54376

Reaction equation

toluene ethyl acetate

2-[4-(benzoxazol-2-yldithio)-3-phenoxyacetamido-2-oxoazetidin-1-yl]-3-methylene-butyric acid diphenylmethyl ester

ozone

O2 O3

→

2-[4-(Benzoxazol-2-yldithio)-3-phenoxyacetamido-2-oxoazetidin-1-yl]-3-hydroxy-crotonic acid diphenylmethyl ester

Solvents

ethyl acetate

Conditions

Workup

1. 1
   ConcentrationThe solution is concentrated by evaporation to about 50 ml in vacuo
2. 2
   workup.ADDITIONmixed with 5 ml of dimethyl sulphide
3. 3
   Otherno longer gives
4. 4
   Othera reaction
5. 5
   ConcentrationThe mixture is concentrated by evaporation in vacuo
6. 6
   workup.DISSOLUTIONthe residue is dissolved in 150 ml of benzene
7. 7
   Washthe solution is washed with water
8. 8
   DryingThe organic phase is dried over sodium sulphate
9. 9
   Concentrationconcentrated by evaporation
10. 10
    OtherThe residue is chromatographed on 150 g of acid-washed silica gel

Procedure

(aix) Approximately one equivalent of ozone (in the form of an O2 /O3 mixture) is passed into a solution, cooled to -70° C., of 3.35 g of 2-[4-(benzoxazol-2-yldithio)-3-phenoxyacetamido-2-oxoazetidin-1-yl]-3-methylene-butyric acid diphenylmethyl ester in 125 ml of ethyl acetate, until starting material is no longer detectable by thin layer chromatography (silica gel; toluene/ethyl acetate, 3:1). The solution is concentrated by evaporation to about 50 ml in vacuo, mixed with 5 ml of dimethyl sulphide and stirred until the potassium iodide/starch test no longer gives a reaction. The mixture is concentrated by evaporation in vacuo, the residue is dissolved in 150 ml of benzene and the solution is washed with water. The organic phase is dried over sodium sulphate and concentrated by evaporation. The residue is chromatographed on 150 g of acid-washed silica gel, using toluene/ethyl acetate, 4:1. 2-[4-(Benzoxazol-2-yldithio)-3-phenoxyacetamido-2-oxoazetidin-1-yl]-3-hydroxy-crotonic acid diphenylmethyl ester is obtained in the form of a white foam; IR spectrum (methylene chloride): characteristic bands at 5.60, 5.90 and 6.0 μ.

Source