Reaktion #66576

Reaktionsgleichung

Methyl (R)-(+)-lactate

Triethylamine

para-toluenesulfonyl chloride

Triethylamine hydrochloride

→

(2R)-2-(4-methylphenoxy)-propanoic acid, methyl ester

Lösungsmittel

acetonitrile

acetonitrile

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.ADDITIONwas added dropwise to the reaction mixture (over 40 mins)
2. 2
   Temperaturmaintaining the temperature below 5° C
3. 3
   workup.ADDITIONAfter complete addition a precipitate
4. 4
   Sonstigeformed which
5. 5
   Filtrationwas filtered
6. 6
   workup.ADDITIONThe filtrate was diluted further with acetonitrile (55 ml)

Vorschrift

Methyl (R)-(+)-lactate (3.33 g) and acetonitrile (16.7 ml) were charged to a flask and the resulting solution cooled to −5° C. Triethylamine (4.9 ml) was added. Triethylamine hydrochloride (0.31 g) was added. A solution of para-toluenesulfonyl chloride (5.8 g) dissolved in acetonitrile (16.7 ml) was added dropwise to the reaction mixture (over 40 mins), maintaining the temperature below 5° C. After complete addition a precipitate formed which was filtered. The filtrate was diluted further with acetonitrile (55 ml), to give (2R)-2-(4-methylphenoxy)-propanoic acid, methyl ester. The solution was treated with potassium carbonate (5 g) and 5-chloro-2-hydroxy benzaldehyde. The reaction mixture was heated at 50° C. for 32 h, then cooled to 20° C., diluted with water (100 ml) and extracted with tert-butyl methyl ether (250 ml). The organic phase was washed (brine), dried (MgSO4) and concentrated in vacuo. The residue was purified by chromatography (silica, 5-20% EtOAc/hexane as eluent) to give the sub-title compound (5.3 g).

Quelle