Reaction #50176

Reaction equation

Tetrahydro-2-(2-propynyloxy)-2H-pyran

tetrahydro-4H-pyran-4-one

ethyl magnesium bromide

→

4-hydroxy-4-[3-(tetrahydropyran-2-yloxy)prop-1-ynyl]tetrahydropyran

Yield 88.3%

Solvents

THF

Conditions

Workup

1. 1
   OtherThe reaction was quenched by addition of crushed ice and saturated aqueous NH4Cl
2. 2
   ExtractionThe resulting two-layered mixture was extracted with ether (3×150 mL)
3. 3
   DryingThe combined organic layers were dried over MgSO4
4. 4
   Filtrationfiltered
5. 5
   Concentrationconcentrated in vacuo
6. 6
   OtherPurification by chromatography on silica gel (200 g, 20% ethyl acetate: hexanes)

Procedure

Tetrahydro-2-(2-propynyloxy)-2H-pyran (21 g, 150 mmol) was converted to the corresponding magnesium anion by deprotonation with ethyl magnesium bromide (75 mL of a 2M solution, 150 mmol) according to the method described in Org. Synth., 60: 81, 7 (1981). The resulting anion was cooled to -20° C. and tetrahydro-4H-pyran-4-one (14.8 g, 148 mmol) in dry THF (30 mL) was added dropwise and the resulting solution stirred for three hours. The reaction was quenched by addition of crushed ice and saturated aqueous NH4Cl. The resulting two-layered mixture was extracted with ether (3×150 mL). The combined organic layers were dried over MgSO4, filtered, and concentrated in vacuo. Purification by chromatography on silica gel (200 g, 20% ethyl acetate: hexanes) provided 4-hydroxy-4-[3-(tetrahydropyran-2-yloxy)prop-1-ynyl]tetrahydropyran(31.4 g, 88%).

Source