Novel atom-economic reaction: comprehensive utilization of S-alkylisothiouronium salt in the synthesis of thioethers and guanidinium salts

A novel atom-economic three-component one-pot reaction of a primary amine, an S-alkylisothiouronium salt and a Michael receptor is reported, which affords a guanidinium salt and thioether simultaneously. The guanidine moiety is involved in catalyzing the conjugated Michael addition of the mercaptan. The reaction proceeds under ambient conditions using a non-toxic EtOH-H2O mixture as the solvent, and the two products can be very easily purified. Complete atom economy is achieved by fully utilizing the S-alkylisothiouronium salt and converting the previously wasted mercaptan by-product into the valuable thioether.