Triethyloxonium Tetrafluoroborate

B(C6F5)3 promoted cyclisation of internal propargyl esters: structural characterisation of 1,3-dioxolium compounds

“…1,3-Dithiolium and 1,3-oxathiolium compounds are known but few 1,3-dioxolium compounds have been isolated. 5 The enhanced stability of the S-analogues has been ascribed to the increased covalency in the s-bonds and increased delocalisation of the pelectrons within the ring affording a more stable heterocyclic system. 6 On the other hand, 1,3-dioxolium ions exhibit substantially more polar localised bonding and are highly reactive, particularly with respect to attack by nucleophiles including water at the C(1) position.…”

“…In the structural studies of 4 and 5, the five-membered heterocycles are essentially planar as evidenced by the maximum deviation from planarity of 0.003 Å (4) and o0.002 Å ( 5) and the phenyl ring at the C(1) position lies essentially in the same plane as the dioxolium ring; the angle between the phenyl and dioxolium ring planes is only 5.211 (4) and 1.181 (5). The co-planarity of the two rings offers some potential for stabilisation of the positive charge by delocalisation, consistent with a shorter C-C single bond length between these rings of 1.427( 3) Å ( 4) and 1.4343(2) Å ( 5).…”

Efficient Synthesis of Alkyl β-Diketimines

“…In compound 4 , conversion of the carbonyl to an imino group requires the use of a strong Lewis acid. Triethyloxonium tetrafluoroborate reagent ( 1 ), commonly referred to as Meerwein’s salt, is often used to convert 4 to 5 . We found that commercial sources of triethyloxonium tetrafluoroborate were unreliable and produced a mixture of products .…”