The influence of steric effects on the regio- and stereospecificity of the addition of thiolates to tert-butylacetylene in a proton-donating medium

1. A method which fully eliminates the competing free-radical reaction was developed for the nucleophilic addition of thiols to alkylacetylenes. 2. Under purely nucleophilic conditions steric effects substantially affect the regioorieatatioa of a thiolate ion adding to tert-butylacetylene. The proportion of attack at theβ atom, of the C ≡ C bond increases with increase in the volume of the nucleophilic reagent. 3. Theβ adducts are formed strictly stereospecifically by a nucleophilic mechanism, of 1,2-anti-addition, and steric effects do not affect the stereochemistry of the process. 4. It was found that the ratio of the regioisomers formed in the reaction of 1-alkynes with thiols and alcohols correlates well with Charton' s steric constants for alkyl groups in the nucleophilic reagent.