“…TMSOTf [32] and Cp 2 Ti(OTf) 2 [40] show high catalytic activity but they are known to be unstable in air (Table 5, Entries 3,4). The reference catalysts of Sc(OTf) 3 [30], Bi(OTf) 3 [33], Mg(NTf 2 ) 2 [23], I 2 [38] and DMAP [5] (highly toxic; e.g., intravenous LD50 in the rat: 56 mg/ kg) [23], and AgOSO 2 C 8 F 17 [43], show lower catalytic activity than Cp 2 Ti(OSO 2 C 8 F 17 ) 2 (Table 5, Entries 5-9). Furthermore, these catalysts are hydrolytic in air and liberate CF 3 SO 3 H which has been considered as powerful catalyst by Hollis et al [42].…”