Triethylamine → tert-Butyl[(5-chloro-4-isocyanato-2-methoxybenzyl)oxy]dimethylsilane

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Reaction Steps

A solution of 4-({[tert-butyl(dimethyl)silyl]oxy}methyl)-2-chloro-5-methoxyaniline (intermediate 39; 300 mg, 1 mmol) in 4 ml of dichloromethane was cooled externally with an ice bath while dropping a solution of triphosgene (108 mg; 0.36 mmol) in 5 ml of dichloromethane. Triethylamine (0.28 ml; 2.01 mmol) was added slowly and the system stirred at room temperature for 3 hr. Half of the solvent is then evaporated in vacuo and 25 ml of pentane added. The white precipitate of ureas was filtered and the filtrate evaporated to dryness giving 311 mg of the title compound that were used without further purification in the next step.

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