[C:1](Cl)(=O)C(Cl)=O.CS(C)=O.[CH:11]1([N:15]2[C:19]3[CH:20]=[CH:21][C:22]([CH2:24][OH:25])=[CH:23][C:18]=3[N:17]([CH3:26])[C:16]2=[O:27])CC[CH2:12]1.C(N(CC)CC)C>ClCCl>[CH2:11]([N:15]1[C:19]2[CH:20]=[CH:21][C:22]([CH:24]=[O:25])=[CH:23][C:18]=2[N:17]([CH2:26][CH3:1])[C:16]1=[O:27])[CH3:12]To a dichloromethane (50 mL) solution of oxalyl chloride (1.47 mL, 16.8 mmol) at −78° C. was added methyl sulfoxide (1.47 mL, 20.5 mmol). After 15 minutes 1-Cyclobutyl-5-hydroxymethyl-3-methyl-1,3-dihydro-benzoimidazol-2-one (2.21 g, 10.0 mmol, in 20 mL dichloromethane) was added. After 20 minutes triethylamine (4.26 mL, 20.6 mmol) was added and the reaction was allowed to warm to 23° C. Upon dilution with saturated sodium bicarbonate and dichloromethane the product was extracted into dichloromethane. The organic layer was dried over sodium sulfate and concentrated to give 1,3-Diethyl-2-oxo-2,3-dihydro-1H-benzoimidazole-5-carbaldehyde (2.17 g).
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