Methyl 4-chloroformylbutyrate → 2-(5-methoxycarbonyl-2-oxopentylidene)-3-methyl-3H-benzothiazole

HRID 1470690Notes

Reaction equation

S(C1C=CC(C)=CC=1)([O-])(=O)=O.[CH3:12][C:13]1[S:14][C:15]2[CH:22]=[C:21](S(O)(=O)=O)[CH:20]=[CH:19][C:16]=2[N+:17]=1[CH3:18].Cl[C:28](=[O:36])[CH2:29][CH2:30][CH2:31][C:32]([O:34][CH3:35])=[O:33]>N1C=CC=CC=1>[CH3:35][O:34][C:32]([CH2:31][CH2:30][CH2:29][C:28](=[O:36])[CH:12]=[C:13]1[N:17]([CH3:18])[C:16]2[CH:19]=[CH:20][CH:21]=[CH:22][C:15]=2[S:14]1)=[O:33]

Participants

Conditions

Temperature: 55 °C

Procedure

To 1.7 g of 2,3-dimethyl-6-sulfobenzothiazolium tosylate in 20 mL of pyridine at room temperature is added 1 mL of methyl 5-chloro-5-oxovalerate. The mixture is heated at 50-60° C. for 3 hours. The pyridine solvent is removed under reduced pressure, and the reaction is worked up with chloroform and brine, and purified by silica gel column to yield 0.5 g of 2-(5-methoxycarbonyl-2-oxopentylidene)-3-methyl-3H-benzothiazole. A mixture of 0.45 g of this benzothiazole and 0.45 g of phosphorous oxychloride in 5 mL of dichloroethane is heated at reflux for 2 hours to generate 2-(2-chloro-2-methoxycarbonylpropylvinyl)-3-methylbenzothiazolium chloride. The volatile components are evaporated and the crude chloride is used without further purification. The crude chloride and 0.5 g of Compound 12 is stirred in 5 mL of dichloroethane in the presence of 0.45 mL of triethylamine for 2 hours. The volatile components are removed under reduced pressure, and the residue is dissolved in 5 mL of methanol and added dropwise to a solution of 4.5 g of sodium iodide in 30 mL water. The sticky solid is purified by HPLC to yield Compound 37.

Workup

customThe pyridine solvent is removed under reduced pressure
custompurified by silica gel column

Sources & evidence

ORD record: ord-ae924e55d63848dead386a29fa1c414e
Source dataset: uspto-grants-2015_04
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US09006469B2

Reaction notes

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