N-bromobutanimide → 3-bromo-6-chloro-2H-chromene

HRID 402114Notes

Reaction equation

HRID 402114 reaction equation
[Li]OC(C)=O.O.O.[Cl:8][C:9]1[CH:10]=[CH:11][C:12]2[O:17][CH2:16][C:15](C(O)=O)=[CH:14][C:13]=2[CH:21]=1.C1C(=O)N([Br:29])C(=O)C1>CC#N.O>[Br:29][C:15]1[CH2:16][O:17][C:12]2[C:13]([CH:14]=1)=[CH:21][C:9]([Cl:8])=[CH:10][CH:11]=2

Participants

5

Reactant 3

HCID 67184N-bromobutanimideHCID 5969296-chloro-2H-chromene-3-carboxylic acidHCID 178526966lithium;acetate;dihydrate

Product 1

HCID 109885633-bromo-6-chloro-2H-chromeneYield 27%

Reagents, catalysts & solvents 1

HCID 18373917Acetonitrile--water (1/1)Solvent

Procedure

To a solution of LiOAc.2H2O (0.16 g, 1.62 mmol) in 97:3 CH3CN/H2O (30 mL) was added 6-chloro-2H-1-benzopyran-3-carboxylic acid (1.43 g, 8.12 mmol), followed by NBS (1.52 g, 8.53 mmol) and the mixture was stirred at room temperature for 5 hours. The reaction mixture was then concentrated to dryness under reduced pressure. Purification by flash column chromatography (gradient, hexanes, then 98:2 to 90:10 hexanes/Et2O) gave 3-bromo-6-chloro-2H-chromene (0.47 g, 27%) as a pale yellow oil: 1H NMR (300 MHz, CDCl3) δ 7.14-7.10 (m, 1H), 6.94-6.88 (m, 2H), 6.79 (d, J=8.1 Hz, 1H), 6.75 (s, 1H), 4.88 (d, J=1.5 Hz, 2H).

Workup

  1. concentrationThe reaction mixture was then concentrated to dryness under reduced pressure
  2. customPurification by flash column chromatography (gradient, hexanes

Sources & evidence

ORD record
ord-dcc022107c7b4815b01ada25a0029059
Source dataset
uspto-grants-2014_06
Patent number
US08741901B2

Reaction notes

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