Reacción #451014

Ecuación de reacción

CF3CO2H

PPTS

paraldehyde

NaHCO3

Paraldehyde

chromene

2,2-Dimethyl-5-hydroxy-6-propionyl-10-propyl-2H,8H-benzo[1,2-b:3,4-b']dipyran-8-one

PPTS

paraldehyde

→

chromanone

Rendimiento 27.0%

12-Oxocalanolide A

Rendimiento 27.0%

Disolventes

1,2-dichloroethane

Condiciones de reacción

Tratamiento posterior

1. 1
   TemperaturaThe resulting mixture was refluxed for 7 h
2. 2
   Temperaturathe mixture was refluxed overnight
3. 3
   Extracciónextracted with ethyl acetate (50 mL×3)
4. 4
   OtroThe crude product obtained by evaporation under reduced pressure
5. 5
   Lavadowas washed with hexane
6. 6
   OtroThe residue was purified by column chromatography
7. 7
   Lavadoeluting with ethyl acetate/hexane (1:2)

Procedimiento

Paraldehyde One-Step Reaction: To a stirring solution of chromene 4 (350 mg, 1.0 mmol) and PPTS (250 mg, 1.0 mmol) in 1,2-dichloroethane (2 mL) at ambient temperature under N2 was added 3 mL paraldehyde (22.5 mmol). The resulting mixture was refluxed for 7 h. Then, CF3CO2H (1 mL), an additional equivalent of PPTS and 1 mL of paraldehyde were added; the mixture was refluxed overnight. The reaction mixture was neutralized with saturated aqueous NaHCO3 and extracted with ethyl acetate (50 mL×3). The crude product obtained by evaporation under reduced pressure was washed with hexane. The residue was purified by column chromatography eluting with ethyl acetate/hexane (1:2) to afford 100 mg (27% yield) of chromanone 7 and 30 mg (8% yield) of 7a. Chromanone 7 (10,11-trans-dihydro-6,6,10,11-tetramethyl-4-propyl-2H,6H,12H-benzo[1,2-b:3,4-b':5,6-b"]tripyran-2,12-dione) obtained by this method was identical with an authentic sample by comparison of TLC, HPLC and spectroscopic data.

Fuente