“…As the next model substrate, the sterically crowded diferrocenyl thioketone (8b) was tested as a structural analogue of thiobenzophenone, which is widely applied in studies involving aromatic thioketones [3][4][5]. However, in contrast to 8a, the reaction of 8b with 5a was unsuccessful; this observation prompted us to replace AlCl3 by scandium triflate (Sc(OTf)3), which is also known to be an efficient catalyst in various reactions of D-A cyclopropanes [9,10,19]. This time, the reaction was complete after 1 h and the expected 2,2-diferrocenyl-substituted tetrahydrothiophene 9b was isolated chromatographically in about 28% yield (Scheme 3, Table 1).…”