Reacción #632004

Ecuación de reacción

2-trimethylsilyl-ethanol

triethylamine

DPPA

product

racemic 2-Ethylcyclopropane-1,1-dicarboxylic acid tert-butyl ester

→

desired product

(1S,2S) 2-ethyl-1-(2-trimethylsilanylethoxycarbonylamino)cyclopropane-carboxylic acid tert-butyl ester

Disolventes

benzene

Condiciones de reacción

Tratamiento posterior

1. 1
   TemperaturaThe reaction mixture was heated
2. 2
   Temperaturato reflux for 3.5 hours
3. 3
   Temperaturaheated
4. 4
   Temperaturato reflux overnight
5. 5
   FiltraciónThe reaction mixture was filtered
6. 6
   workup.ADDITIONdiluted with diethyl ether
7. 7
   Lavadowashed sequentially with 10% aqueous citric acid solution, water, saturated aqueous NaHCO3, water (2×), and brine (2×)
8. 8
   Secadodried (MgSO4)
9. 9
   Filtraciónfiltered
10. 10
    Concentraciónconcentrated in vacuo
11. 11
    Filtraciónfiltered

Procedimiento

To a suspension of the product of Step 2 (10 g, 46.8 mmol) and 3 g of freshly activated 4 Å molecular sieves in dry benzene (160 mL) was added triethylamine (7.50 mL, 53.8 mmol) and DPPA (11 mL, 10.21 mmol). The reaction mixture was heated to reflux for 3.5 hours, treated with 2-trimethylsilyl-ethanol (13.5 mL, 94.2 mmol), and heated to reflux overnight. The reaction mixture was filtered, diluted with diethyl ether, washed sequentially with 10% aqueous citric acid solution, water, saturated aqueous NaHCO3, water (2×), and brine (2×), dried (MgSO4), filtered, and concentrated in vacuo. The residue was suspended with 10 g of Aldrich polyisocyanate scavenger resin in 120 mL of dichloromethane, stirred at room temperature overnight, and filtered to provide the desired product (8 g, 24.3 mmol; 52%) as a pale yellow oil: 1H NMR (CDCl3) δ 0.03 (s, 9H), 0.97 (m, 5H), 1.20 (br m, 1H), 1.45 (s, 9H), 1.40-1.70 (m, 4H), 4.16 (m, 2H), 5.30 (br s, 1H).

Fuente