Formaldehyde → 7-bromo-2-methylene-3,4-dihydronaphthalen-1(2H)-one

HRID 1911004Notes

Reaction equation

HRID 1911004 reaction equation
[Br:1][C:2]1[CH:11]=[C:10]2[C:5]([CH2:6][CH2:7][CH2:8][C:9]2=[O:12])=[CH:4][CH:3]=1.F[C:14](F)(F)C([O-])=O.C[NH2+]C1C=CC=CC=1.C=O>C1COCC1>[Br:1][C:2]1[CH:11]=[C:10]2[C:5]([CH2:6][CH2:7][C:8](=[CH2:14])[C:9]2=[O:12])=[CH:4][CH:3]=1

Participants

5

Reactant 3

HCID 712FormaldehydeHCID 2527317-Bromo-1,2,3,4-tetrahydronaphthalen-1-oneHCID 2724109N-Methylanilinium trifluoroacetate

Product 1

HCID 111839757-bromo-2-methylene-3,4-dihydronaphthalen-1(2H)-oneYield 40.4%

Reagents, catalysts & solvents 1

HCID 8028TetrahydrofuranSolvent

Procedure

A solution of 7-bromo-3,4-dihydronaphthalen-1(2H)-one (2.00 g, 8.89 mmol) in THF (50 mL) was added to a mixture of N-methylanilinium trifluoroacetate (2.95 g, 13.3 mmol) and paraformaldehyde (1.20 g, 40.0 mmol) at rt. The resulting mixture was heated at reflux for 6 hours. The oil bath was removed and the mixture was allowed to cool to rt. Diethyl ether was added to the reaction mixture, which induced the separation of a red gum. The ethereal solution was decanted from the red gum into a separatory funnel and washed with half-saturated sodium bicarbonate solution. The red gum was triturated with diethyl ether, and the resulting ethereal solution was then used to extract the washing water. The combined organic layers were dried over magnesium sulfate. Filtration and concentration of the organic layer afforded a heavy red oil. The oil was purified using silica gel column chromatography (20:1 hexanes/EtOAc) to afford 7-bromo-2-methylene-3,4-dihydronaphthalen-1(2H)-one (0.850 g, 3.59 mmol, 40% yield) as a thick viscous yellow oil. 1H NMR (400 MHz, chloroform-d) δ 8.23 (d, J=2.0 Hz, 1H), 7.60 (dd, J=8.2, 2.1 Hz, 1H), 7.16 (d, J=8.3 Hz, 1H), 6.26 (q, J=1.3 Hz, 1H), 5.50 (q, J=1.7 Hz, 1H), 3.01-2.91 (m, 2H), 2.91-2.82 (m, 2H).

Workup

  1. temperatureThe resulting mixture was heated
  2. temperatureat reflux for 6 hours
  3. customThe oil bath was removed
  4. additionDiethyl ether was added to the reaction mixture, which
  5. customthe separation of a red gum
  6. customThe ethereal solution was decanted from the red gum into a separatory funnel
  7. washwashed with half-saturated sodium bicarbonate solution
  8. customThe red gum was triturated with diethyl ether
  9. extractionto extract the washing water
  10. dry with materialThe combined organic layers were dried over magnesium sulfate
  11. filtrationFiltration and concentration of the organic layer
  12. customafforded a heavy red oil
  13. customThe oil was purified

Sources & evidence

ORD record
ord-925a6183470c491c9902a0fa8ea83d42
Source dataset
uspto-grants-2013_12
Patent number
US08604024B2

Reaction notes

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