Dibromomethane → (S)-2-methyl-4-methylidene-3-(2-propynyl)-1-tert-butyldimethylsilyloxycyclopent-2-ene

HRID 1078997Notes

Reaction equation

HRID 1078997 reaction equation
BrCBr.O1CCC[CH2:5]1.[Si:9]([O:16][C@H:17]1[CH2:21][C:20](=O)[C:19]([CH2:23][C:24]#[CH:25])=[C:18]1[CH3:26])([C:12]([CH3:15])([CH3:14])[CH3:13])([CH3:11])[CH3:10].C(=O)(O)[O-].[Na+]>ClCCl.[Zn].[Ti](Cl)(Cl)(Cl)Cl.O.CCCCCC>[CH3:26][C:18]1[C@@H:17]([O:16][Si:9]([C:12]([CH3:15])([CH3:14])[CH3:13])([CH3:11])[CH3:10])[CH2:21][C:20](=[CH2:5])[C:19]=1[CH2:23][C:24]#[CH:25]

Participants

10

Reactant 4

HCID 3024DibromomethaneHCID 8028Tetrahydrofuran2×HCID 516892Sodium BicarbonateHCID 11043662(S)-4-tert-butyldimethylsilyloxy-3-methyl-2-(2-propynyl)cyclopent-2-ene-1-one

Product 1

HCID 11821434(S)-2-methyl-4-methylidene-3-(2-propynyl)-1-tert-butyldimethylsilyloxycyclopent-2-eneYield 68.7%

Reagents, catalysts & solvents 5

HCID 23994ZincCatalystHCID 24193Titanium TetrachlorideCatalystHCID 962WaterSolventHCID 6344DichloromethaneSolvent2×HCID 8058HexaneSolvent

Procedure

1H-NMR (solvent: CDCl3, internal standard: TMS) δ value (ppm): 4.69(brd, 1H), 3.11(ABq, 2H), 2.74(dd, 1H), 2.28(dd, 1H), 2.16(s, 3H), 1.96(t, 1H), 0.92(s, 9H), 0.15(s, 3H), 0.12(s, 3H). 2 Dibromomethane (13.04 g) and zinc dust (14.71 g) were added to tetrahydrofuran (120ml), and the resulting mixture was cooled to 0°~5° C. A dichloromethane solution (50 ml) of 1M titanium tetrachloride was added to the tetrahydrofuran solution over about 10 min, and the resulting mixture was allowed to react for 3 days at 0°~5° C. Then a solution of (S)-4-tert-butyldimethylsilyloxy-3-methyl-2-(2-propynyl)cyclopent-2-ene-1-one (13.22 g) in dichloromethane (50 ml) was added at 0°~5° C. over about 10 min. After the reaction was continued for 2 hours at the same temperature, hexane (200 ml) and then a slurry consisting of sodium bicarbonate (75 g) and water (40 ml) were added After stirring for 2 hours at 0°~5° C., the organic layer was separated by decantation. The obtained residue was extracted three times with n-hexane (200 ml). The combined organic layer was washed with saturated aqueous sodium bicarbonate solution, and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure, and the resultant residue was subjected to silica gel column chromatography (eluent; n-hexane: ethyl acetate=50:1) to afford the desired product, (S)-2-methyl-4-methylidene-3-(2-propynyl)-1-tert-butyldimethylsilyloxycyclopent-2-ene (9.02 g, yield 68.7%) as a pale yellow oil.

Workup

  1. temperaturethe resulting mixture was cooled to 0°~5° C
  2. customto react for 3 days at 0°~5° C
  3. additionwere added
  4. customthe organic layer was separated by decantation
  5. extractionThe obtained residue was extracted three times with n-hexane (200 ml)
  6. washThe combined organic layer was washed with saturated aqueous sodium bicarbonate solution
  7. dry with materialdried over anhydrous sodium sulfate
  8. customThe solvent was evaporated under reduced pressure

Sources & evidence

ORD record
ord-5540c9f93f7045289ad831cc82e1ba82
Source dataset
uspto-grants-1996_08
Patent number
US05550260

Reaction notes

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