Benzyl chloroformate (CbzCl) synthesis using carbon monoxide as a carbonyl source

A novel non-phosgene synthetic method for benzyl chloroformate (CbzCl) was established. S-Methyl O-benzyl carbonothioates were prepared by the carbonylation of benzyl alcohols with carbon monoxide and sulfur (or carbonyl sulfide) in the presence of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) followed by esterification using methyl iodide in good yields. Then, CbzCl derivatives were successfully synthesized by the chlorination of S-methyl O-benzyl carbonothioates using sulfuryl chloride in excellent yields.