Benzene → Benzopyran

HRID 1651610Notes

Reaction equation

HRID 1651610 reaction equation
[O:1]1[C:10]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[CH:4](O)[CH2:3][CH2:2]1.C1C=CC=CC=1.C1(C)C=CC(S(O)(=O)=O)=CC=1>O>[O:1]1[C:10]2[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=2[CH:4]=[CH:3][CH2:2]1

Participants

5

Reactant 3

HCID 241BenzeneHCID 6101p-Toluenesulfonic acidHCID 92890Chroman-4-ol

Product 1

HCID 9211BenzopyranYield 764.2%

Reagents, catalysts & solvents 1

HCID 962WaterSolvent

Procedure

A mixture of 4-chromanol (30 g; 0.02 mole), benzene (200 ml) and 4-toluenesulfonic acid (200 mg) was refluxed, with a Dean-Stark trap, until separation of water ceased (ca. 3 hrs.). It was then washed successively with saturated NaHCO3 aqueous solution and water, dried over anhydrous MgSO4 and evaporated under reduced pressure to yield an almost colorless liquid which was distilled under vacuum to give benzopyran (20.2 g, 76.4%) b.p. 73°-78°/3 torr.

Workup

  1. custom(ca. 3 hrs.)
  2. washIt was then washed successively with saturated NaHCO3 aqueous solution and water
  3. dry with materialdried over anhydrous MgSO4
  4. customevaporated under reduced pressure
  5. customto yield an almost colorless liquid which
  6. distillationwas distilled under vacuum

Sources & evidence

ORD record
ord-779d42b040fd4fb79886789b42cd5bd1
Source dataset
uspto-grants-1990_05
Patent number
US04929627

Reaction notes

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