[CH3:1][O:2][C:3]1[C:4]([CH3:19])=[C:5]([CH3:18])[C:6]2[O:11][C:10]([C:13](O)=[O:14])([CH3:12])[CH2:9][CH2:8][C:7]=2[C:16]=1[CH3:17].S(Cl)([Cl:22])=O>CN(C)C=O.ClCCCl>[CH3:1][O:2][C:3]1[C:4]([CH3:19])=[C:5]([CH3:18])[C:6]2[O:11][C:10]([C:13]([Cl:22])=[O:14])([CH3:12])[CH2:9][CH2:8][C:7]=2[C:16]=1[CH3:17]To a solution composed of 3.0 g of (3,4-dihydro-6-methoxy-2,5,7,8-tetramethyl-2H-benzopyran-2-yl)carboxylic acid, 2 drops of N,N-dimethylformamide and 50 ml of 1,2-dichloroethane was added 1.1 ml of thionyl chloride and the mixture was refluxed for 2 hours. After cooling, the reaction mixture was evaporated under reduced pressure to remove the low-boiling substances. This procedure gave (3,4-dihydro-6-methoxy-2,5,7,8-tetramethyl-2H-benzopyran-2-yl)carbonyl chloride in a quantitative yield of 3.39 g.
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