Acetic Acid → ethyl 3,4-dihydro-1H-2-benzopyran-1-acetate

HRID 1417840Notes

Reaction equation

HRID 1417840 reaction equation
[OH:1][CH2:2][CH2:3][C:4]1[CH:16]=[CH:15][CH:14]=[CH:13][C:5]=1[CH:6]=[CH:7][C:8]([O:10][CH2:11][CH3:12])=[O:9].CC(C)([O-])C.[K+].C(O)(=O)C>C1COCC1>[CH:6]1([CH2:7][C:8]([O:10][CH2:11][CH3:12])=[O:9])[C:5]2[C:4](=[CH:16][CH:15]=[CH:14][CH:13]=2)[CH2:3][CH2:2][O:1]1

Participants

5

Reactant 3

HCID 176Acetic AcidHCID 23665647Potassium tert-butoxideHCID 54089289Ethyl 2-(2-hydroxyethyl)cinnamate2×

Product 1

HCID 10822798ethyl 3,4-dihydro-1H-2-benzopyran-1-acetate

Reagents, catalysts & solvents 1

HCID 8028TetrahydrofuranSolvent2×

Procedure

Ethyl 2-(2-hydroxyethyl)cinnamate (CXXX, EXAMPLE 112, theoretically 2.40 moles) is dissolved in THF (2.4 liters) and cooled to 0°. Potassium t-butoxide (5 mol %, 120 ml of a 1 molar THF solution) is added via syringe. After 5 min HPLC shows the cyclization is completed. Acetic acid (6 mol %, 8.2 ml, 144 mmol) is added. The slurry is filtered through approximately 300 g of 200 mesh silica gel. The solvent is removed under reduced pressure until approximately 0.5 liter of THF remained. Diatomaceous earth (100 g) is added followed by hexane (4.5 liters). This slurry is filtered through 200 mesh silica gel (400 g), washing with THF/hexane (1/9) until TLC shows no remaining product. Solvent removal gives the title compound. This material is filtered through silica gel more carefully, giving an analytical sample of the title compound, NMR (300 MHz, CDCl3) 7.1-7.2, 7.05, 5.26, 4.23, 4.12, 3.83, 3.0-2.7, 1.28; high resolution MS calculated for 220.1099, found 220.1105.

Workup

  1. temperaturecooled to 0°
  2. filtrationThe slurry is filtered through approximately 300 g of 200 mesh silica gel
  3. customThe solvent is removed under reduced pressure until approximately 0.5 liter of THF
  4. additionDiatomaceous earth (100 g) is added
  5. filtrationThis slurry is filtered through 200 mesh silica gel (400 g)
  6. washwashing with THF/hexane (1/9) until TLC
  7. customSolvent removal

Sources & evidence

ORD record
ord-4ab4aed9a3da4ae89a573ac98bce67a7
Source dataset
uspto-grants-1999_03
Patent number
US05877317

Reaction notes

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