New Method for the Synthesis of Sulforaphane and Related Isothiocyanates

The biologically important isothiocyanate sulforaphane (4-isothiocyanatobutyl methyl sulfoxide) was synthesized in six simple steps from commercially available 4-aminobutan-1-ol with an overall yield of 64%. The new synthetic method is suitable for multigram-scale preparation of sulforaphane and does not require expensive or toxic reagents. A novel one-pot procedure was also developed for preparing isothiocyanates through reaction of amines with O-phenyl chlorothioformate under mild conditions. Additionally, methyl pyrrolidine-1-carbodithioate was obtained as an unexpected byproduct, and this protocol was shown to be useful for the synthesis of S-aryl or S-heterocyclic thiocarbamates with cyclic side chains.