Dimethylformamide → Chroman-6-carbaldehyde

HRID 1912539Notes

Reaction equation

HRID 1912539 reaction equation
I[C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][CH:11]=1)[O:8][CH2:7][CH2:6][CH2:5]2.[Li]CCCC.CN(C)[CH:19]=[O:20]>O1CCCC1>[O:8]1[C:9]2[C:4](=[CH:3][C:2]([CH:19]=[O:20])=[CH:11][CH:10]=2)[CH2:5][CH2:6][CH2:7]1

Participants

5

Reactant 3

HCID 6228DimethylformamideHCID 109451636-IodochromanHCID 178418339Butyllithium

Product 1

HCID 6504215Chroman-6-carbaldehyde

Reagents, catalysts & solvents 1

HCID 8028TetrahydrofuranSolvent

Procedure

A solution of 6-iodochroman (13.8 g, 53.1 mmol) in tetrahydrofuran (THF) (143 mL) was cooled to −78° C. in a dry ice/acetone bath and then treated with n-BuLi, 2.5M solution in hexanes (23.35 mL, 58.4 mmol). The mixture was stirred for 10 minutes before being treated with N,N-dimethylformamide (6.16 mL, 80 mmol) and the resultant was warmed to ambient temperature and stirred for 10 minutes. The mixture was quenched with saturated NH4Cl and extracted with ethyl acetate. The extracts were washed with brine, dried over Na2SO4, filtered and concentrated to afford the crude chroman-6-carbaldehyde as a yellow solid which was used without further purification. LC/MS (m/z) ES+=163.22 (M+1). A solution of the crude chroman-6-carbaldehyde, methyl 3-oxobutanoate, piperidine (0.263 mL, 2.66 mmol) and AcOH (0.152 mL, 2.66 mmol) in Benzene (113 mL) was refluxed (DS-trap) overnight. The mixture was concentrated and diluted with ethyl acetate. The dilution was washed with brine, dried over sodium sulfate, filtered and concentrated. The residue was purified on silica gel (0-30% hexanes/ethyl acetate) the afford methyl 2-(chroman-6-ylmethylene)-3-oxobutanoate (mixture of E and Z isomers, 8.352 g, 32.08 mmol, 60.47% yield) as a thick yellow oil. 1H NMR (400 MHz, CHLOROFORM-d, major isomer) δ ppm 7.48 (s, 1 H), 7.22-7.12 (m, 2 H), 6.78 (d, J=8.6 Hz, 1 H), 4.27-4.18 (m, 2 H), 3.92-3.81 (m, 3 H), 2.77 (t, J=6.3 Hz, 2 H), 2.39 (s, 3 H), 2.06-1.99 (m, 2 H); 1H NMR (400 MHz, CHLOROFORM-d, minor isomer) δ ppm 7.58 (s, 1 H), 7.16-7.08 (m, 2 H), 6.79-6.71 (m, 1 H), 4.23-4.18 (m, 2 H), 3.84-3.78 (m, 3 H), 2.76 (t, J=6.4 Hz, 2 H), 2.38 (s, 3 H), 2.03-1.96 (m, 2 H); LC/MS (m/z) ES+=261.2 (M+1).

Workup

  1. stirringstirred for 10 minutes
  2. customThe mixture was quenched with saturated NH4Cl
  3. extractionextracted with ethyl acetate
  4. washThe extracts were washed with brine
  5. dry with materialdried over Na2SO4
  6. filtrationfiltered
  7. concentrationconcentrated

Sources & evidence

ORD record
ord-8bb4aa42b8f84cbeb4d102d18d6e4d52
Source dataset
uspto-grants-2013_12
Patent number
US08609653B2

Reaction notes

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