Reacción #67932

Ecuación de reacción

I2

ethyl 2-bromoisobutyrate

pyridine

Benzyl carbazate

→

2-(N′-benzyloxycarbonyl-hydrazino)-2-methyl-propionic acid ethyl ester

Disolventes

—

hexanes

ethyl acetate

DMF

Condiciones de reacción

Tratamiento posterior

1. 1
   OtroFrom two separate
2. 2
   workup.ADDITIONaddition funnels
3. 3
   TemperaturaHeating
4. 4
   Otrothe reaction to completion
5. 5
   Temperaturato cool
6. 6
   workup.ADDITIONpoured onto ice water
7. 7
   ExtracciónThe aqueous mixture was extracted with ethyl ether
8. 8
   Otrothe solvent was removed in vacuo

Procedimiento

Benzyl carbazate (25 g, 0.15 mol) was dissolved in 50 mL of DMF in a round bottom flask. The solution was heated to 95-100° C. From two separate addition funnels, ethyl 2-bromoisobutyrate (58.5 g, 0.3 mol) and pyridine (29.7 g, 0.375 mol, 30 mL) were added drop-wise separately and simultaneously over 30-120 minutes. Heating was continued if necessary to propel the reaction to completion. The reaction was monitored by TLC (30% ethyl acetate in hexanes, I2 visualization). The mixture was allowed to cool, and then poured onto ice water. The aqueous mixture was extracted with ethyl ether, and the solvent was removed in vacuo. 2-(N′-benzyloxycarbonyl-hydrazino)-2-methyl-propionic acid ethyl ester was isolated, optionally after silica gel chromatography. 1H NMR (300 MHz, CDCl3) δ (ppm): 7.36 (br s, 5H), 6.6 (br s, 1H), 5.15 (br s, 2H), 4.2 (q, 2H), 1.3 (s, 6H), 1.25 (t, 3H). 1H NMR analysis alone is insufficient to ascertain the extent of the reaction.

Fuente