Dication ethers. 7. Dication ether salts from cyclic bisureas

Abstract

The bicyclic bisureas 2 react with triflic anhydride to give the dication ether salts 4. Further transformation of the remaining carbonyl groups of 4 into bis‐carbenium ether linkages was not possible. The monocyclic bisurea 8 yields the dicationic heterocycle 9 in an intramolecular fashion. The structure of 9, which is the first dication ether salt with an endocyclic ether linkage, was established by independent synthesis from 10 as well as by its hydrolysis to give the hemi‐protonated bisurea 11.

Hexaalkylguanidinium Trifluoromethanesulfonates – A General Synthesis from Tetraalkylureas and Triflic Anhydride, and Properties as Ionic Liquids

“…Thus, the reaction of dication ether salt 6 with diethylamine generated the low‐melting cyclic guanidinium salt 7 (Scheme ), which in retrospect constitutes one of the early examples of a guanidinium‐based IL. The analogously prepared N ‐phenylated guanidinium salt 8 , on the other hand, is a high‐melting solid 29. We have now returned to these isolated observations to develop a general synthesis of hexaalkylguanidinium triflates from tetraalkylureas, and have found that many of these salts are room‐temperature ILs.…”