Highly stereoselective method to prepare bis-phenylchalcogen alkenes via addition of chalcogenolate to phenylseleno alkynes

The preparation of bis-phenylchalcogen alkenes starting from phenylseleno alkynes is described. The nucleophilic species of selenium, tellurium and sulfur were generated in situ from the reaction of the respective diphenyl dichalcogenide with NaBH₄ in PEG-400 as solvent. The chalcogenolate anions were efficiently and selectively added to a variety of phenylselenoalkynes at mild conditions, furnishing the respective (Z)-1,2-bis-phenylchalcogen alkenes in good yields.