[CH3:1][N:2]([CH3:6])[C:3](Cl)=[S:4].[CH3:7][O:8][C:9]1[C:10]([OH:17])=[C:11]([CH:14]=[CH:15][CH:16]=1)[CH:12]=[O:13].[OH-].[K+]>O1CCCC1.O>[CH3:1][N:2]([CH3:6])[C:3]([O:17][C:10]1[C:9]([O:8][CH3:7])=[CH:16][CH:15]=[CH:14][C:11]=1[CH:12]=[O:13])=[S:4]A solution of N,N-dimethylthiocarbamoyl chloride (10 g) in tetrahydrofuran (40 ml) was added dropwise at <12° C. over 30 minutes to a stirred solution of 3-methoxy-2-hydroxybenzaldehyde (12.3 g) and potassium hydroxide (4.6 g) in water (105 ml) then the mixture was stirred at ambient temperature for 15 minutes. 10% Aqueous potassium hydroxide solution (30 ml) was added, then the product was extracted into toluene (3×150 ml). The combined extracts were washed with water (150 ml) then dried (MgSO4). The solvents were removed in vacuo and the residue was crystallised from methanol to give 2-(N,N-dimethylthiocarbamoyloxy)-3-methoxybenzaldehyde (10.5 g) as a yellow solid which was used without further purification.
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