Reaction #808003

Reaction equation

borane dimethyl sulphide

(R)-tetrahydro-1-methyl-3,3-diphenyl-1H,3H-pyrrolo[1,2-c][1,3,2]oxazaborole

HCl

borane dimethyl sulphide

tert-butyl 2-(2,2-dimethyl-4H-1,3-benzodioxin-6-yl)-2-oxoethylcarbamate

→

title compound

Yield 85.7%

tert-Butyl (2R)-2-(2,2-dimethyl-4H-1,3-benzodioxin-6-yl)-2-hydroxyethylcarbamate

Yield 85.7%

Solvents

THF

toluene

THF

THF

Conditions

Workup

1. 1
   Otherthe temperature below 5°
2. 2
   Temperaturewith cooling
3. 3
   Otherthe mixture was partitioned between ethyl acetate and water
4. 4
   WashThe organic layer was washed with saturated NaHCO3 solution and brine
5. 5
   Dryingdried (MgSO4)
6. 6
   ConcentrationThe solution was concentrated
7. 7
   Otherthe product purified by chromatography on flash silica gel (800 g)
8. 8
   Washeluting successively with hexane:ethyl acetate (4:1

Procedure

A 2M solution of borane-dimethyl sulphide in THF (28 ml) was added slowly to a 1M solution of (R)-tetrahydro-1-methyl-3,3-diphenyl-1H,3H-pyrrolo[1,2-c][1,3,2]oxazaborole in toluene (56 ml) at 0° under nitrogen. A solution of tert-butyl 2-(2,2-dimethyl-4H-1,3-benzodioxin-6-yl)-2-oxoethylcarbamate, (108.2 g) in THF (1.3 liters) was added slowly keeping the temperature below 5° followed by 2M solution of borane-dimethyl sulphide in THF (252 ml) over 50 min. After 1 h, 2M HCl (170 ml) was added with cooling and the mixture was partitioned between ethyl acetate and water. The organic layer was washed with saturated NaHCO3 solution and brine and dried (MgSO4). The solution was concentrated and the product purified by chromatography on flash silica gel (800 g), eluting successively with hexane:ethyl acetate (4:1 then 3:1) to give the title compound (93.3 g), LCMS RT=3.31 min.

Source