Many research groups around the world have been looking for efficient synthetic methods which would allow introduc­ tion of the thioether functionality into unsaturated systems. The hydrothiolation reaction, known also as the thiol–ene or thiol–yne coupling, has attracted significant attention because of its simplicity and practical use in various fields of chemistry and materials science. Moreover, the reaction conditions are very mild in the majority of reports. For many years, the main area of concern at the Depart­ ment of Organometallic Chemistry, Adam Mickiewicz Univer­ sity in Poznań has been broadly defined as organosilicon che­ mistry. Recently, the research work of Dr. Grzegorz Hreczycho's group has also been directed towards novel applications of unsaturated organosilicon compounds in reactions catalyzed by Lewis acids. As Dr. Hreczycho put it: " After the successful O-silylation of silanols and silanediols by alkenylsilanes, we decided to extend our work on the O–H bond to other groups with similar properties, like S–H. " Surprisingly, the formation of an Si–S bond was not observed. Instead of Si–S coupling, the selective hydrothiolation of allylsilanes was observed (Scheme 1). Professor Marciniec, one of the authors of this work, commented: " A lot of scientists would have moved on, but our group always faces the problems. We therefore decided to exploit this unpredicted activity to achieve novel ap­ plications of the hydrothiolation of organosilicon compounds. " " To the best of our knowledge, all earlier research on the addition of thiols to allylsilanes has been based on free­radical reactions. In these, the substrates are activated by tempera­ ture, UV radiation or free-radical generators and as far as we know, no catalytic method of allylsilane hydrothiolation has yet been reported, " said Dr. Hreczycho. " The graduate student Krzysztof Kuciński – who is working towards his doctorate under the supervision of Dr. Piotr Pawluć – started with tests of various catalysts and solvents. Scandium(III), bismuth(III), indium(III) and samarium(III) triflates were considered as ca­ talyst for this process, " he continued. " Among the above-men­ tioned triflates, only scandium(III) triflate and indium(III) trif­ late were found to be active catalysts, although scandium(III) triflate demonstrated the highest activity and selectivity in the hydrothiolation reaction. Tolu ene and fluorobenzene pro­ ved to be the most suitable solvents for this process. " Sub­ sequently, the nature of substituents attached to silicon and sulfur was examined and proved to be insignificant for the reaction. The use of allylsilanes in hydrothiolation catalyzed by scandium(III) triflate led to the products consistent with Markovnikov's rule (Scheme 2). This result was confirmed by