反応 #4834

反応方程式

thionyl chloride

Vilsmeier reagent

2,6-dimethylpiperidine

(-)-α-Hydroxy-2-nitrobenzenepropanoic acid

→

(+)-α-Chloro-2-Nitrobenzenepropanoic Acid 2,6-Dimethylpiperidine Salt

溶媒

N,N-dimethylformamide

dichloromethane

ether

ethanol

dichloromethane

反応条件

後処理

1. 1
   workup.ADDITIONThe solution was added
2. 2
   workup.STIRRINGthe mixture was stirred for 1 hour, during which time it
3. 3
   その他The dichloromethane solution was separated
4. 4
   洗浄washed thrice with water
5. 5
   乾燥dried (MgSO4)
6. 6
   その他Evaporation
7. 7
   その他gave a syrup which
8. 8
   workup.WAITwas subjected to an oil pump vacuum for 1.5 hours
9. 9
   その他The crude titled product [2.98 g. (61%), m.p. 155°-158° C. dec.] crystallized readily
10. 10
    その他Two crystallizations (methanol-ether) with decolorization (Nuchar C-190N)
11. 11
    その他gave 1.91 g

実験手順

To magnetically stirred N,N-dimethylformamide (3 mL) cooled in ice was added slowly dropwise thionyl chloride (4.5 ml., 61.7 mmol) and the resulting cold Vilsmeier reagent was diluted with dichloromethane (30 ml.). (-)-α-Hydroxy-2-nitrobenzenepropanoic acid [3.00 g., 14.2 mmol, [α]D25 -63.04° (c 0.955, 95% ethanol)] in dichloromethane (70 ml.) was added. The resulting solution, protected from moisture, was left at room temperature (25° overnight. The solution was added to stirred ice and the mixture was stirred for 1 hour, during which time it warmed to room temperature. The dichloromethane solution was separated and washed thrice with water and dried (MgSO4). Evaporation gave a syrup which was subjected to an oil pump vacuum for 1.5 hours. The syrup was dissolved in ether and 2,6-dimethylpiperidine was added to approximate neutrality (pH 9 with pH paper). The crude titled product [2.98 g. (61%), m.p. 155°-158° C. dec.] crystallized readily. Two crystallizations (methanol-ether) with decolorization (Nuchar C-190N) gave 1.91 g. (39%) of pure product; m.p. 164°-167° C. dec., [α]D25 +42.11° (c 1.09, 95% ethanol).

出典