Relative stabilities of mono- and dioxolenium ions

Chemistry of N-cyanodithioimidocarbonic acid. II. Synthesis of 3-halo-1,2,4-thiadiazoles

“…Rather surprisingly, water also served as solvent media for chlorine or bromine cyclizations. 18 In the conversion of the monoesters to thiadiazole sulfides a diagnostic change was noted in the infrared spectra. To illustrate, monoesters exhibit a strong absorption at 1340-1380 cm"1 as described above.…”

1,3-Dioxolan-2-ylium and related heterocyclic cations

“…Trityl carbonium ion salts were also effective in abstracting hydride from substituted 2-methyl-and 2-phenyl-1,3-dioxolanes ( 87). The open-chain 1,3-propanediolhaloacetates (88) (as well as their tosylates and brosylates) were also converted to the l,3-dioxan-2-ylium ions by AgBF4, The highest yields of ion 86 obtained from 85 or 87 occurred when R4 = R4 = H and R2 = R3. The cyclizations from 88 to 86 gave best yields when R2 = R3 = H. Kabuss81 reported the formation of l,3-dioxolan-2-ylium and l,3-dioxan-2-ylium ions (89 and 90) from their ketals by removal of a 2-alkyl group by Lewis acids including oxonium ions (eq 51 and 52).…”

Theoretical studies of five-membered ring ketene acetals

“…The high stability of 2-substituted-1,3-dioxolan-2-ylium ions is illustrated by their quantitative formation from the corresponding 2-substituted-1,3-dioxolanes via hydride abstraction by the stable triphenylmethyl cation [21]. Dioxonium ions have much lower heats of formation than alkyl cations in the gas phase [42,43] and in strong acid solutions [44,45]. The literature regarding the five-membered ring heterocyclic cations, 11-16, and their six-membered ring analogs has been reviewed [46].…”