Double transacetalization of diacylium ions

Abstract

A novel gas‐phase reaction of diacylium ions of the OCX+CO type (X = N, CH) is reported: double transacetalization with cyclic acetals or ketals. The reaction is exothermic and highly efficient, and forms members of a new class of highly charged‐delocalized ions: cyclic ionic diketals. Pentaquadrupole double‐ and triple‐stage mass spectrometric (MS2 and MS3) experiments reveal the high double transacetalization reactivity of OCN+CO and OCCH+CO, whereas the synthesis of differently substituted cyclic ionic diketals is performed in MS3 experiments via sequential mono‐ and double transacetalization of OCN+CO and OCCH+CO with different acetals. With cyclic acetals, the acylium‐thioacylium ion OCN+CS reacts promptly and selectively by mono‐transacetalization at its acylium site, but the free thiacylium site of its cyclic ionic ketal is nearly unreactive by double transacetalization. Therefore, only the acylium site of OCN+CS can be efficiently protected by transacetalization. Low‐energy MS3 collision‐induced dissociation of the cyclic ionic diketals of OCN+CO and OCCH+CO sequentially frees each of the protected acylium site to form the mono‐derivatized ion, and then the fully deprotected diacylium ion. Copyright © 2000 John Wiley & Sons, Ltd.

Polar Acetalization and Transacetalization in the Gas Phase: The Eberlin Reaction

“…Any reactant ion with a Lewis acid site able to participate in electrophilic addition and a Lewis basic site able to effect nucleophilic ring-closure is in principle eligible to undergo the Eberlin reaction. Indeed, the reaction has been observed not only for acylium ions (R−C + O) but also for many other amphoteric ions such as thioacylium (R−C + S), , carboxonium (H 2 CO + −R), carbosulfonium (H 2 CS + −R), distonic or distonoid radical acylium ( • R−C + O, R = alkyl, allyl, or phenyl), , diacylium (OCN + CO), , sulfinyl (R−S + O), , arylsulfenium (ArS + ), borinium ((RO) 2 B + ), silylium ((RO) 3 Si + ), phosphonium (R 2 P + O), , arylnitrenium (ArNH + ), nitronium (NO 2 + ) 153 and hetarynium ions (2-pyridyl, 2-pyrrolyl cations, and their analogues) …”

“…They can be prepared by the reaction of simple diones with vicinal diols in acidic solution . In the gas phase, an interesting double polar transacetalization of sing ly c harged diacylium ions of the OCX + CO type (X = N, CH) with cyclic acetals has been reported. , The reaction is exothermic and highly efficient and forms a new type of highly charge-delocalized ion, an ionic diacetal (Scheme d). In the case of the reaction of OCN + CO with 2-methyl-1,3-dioxolane, ab initio calculations show that mono-transacetalization is exothermic by 33.3 kcal/mol, while the double transacetalization is 43.1 kcal/mol exothermic .…”

“…The prototype Eberlin reactant ions are amphoteric acylium ions (R−C + O). Many other amphoteric ions bearing both a Lewis acidic and a basic site have also been employed including thioacylium (R−C + S), , carboxonium (H 2 CO + −R), carbosulfonium (H 2 CS + −R), distonic or distonoid radical acylium ( • R−C + O, R = alkyl, allyl, or phenyl), , singly charged diacylium (OCN + CO), , sulfinyl (R−S + O), , arylsulfenium (ArS + ), borinium (RO) 2 B + , silylium ((RO) 3 Si + ), phosphonium (R 2 P + O), , arylnitrenium (ArNH + ), nitronium (NO 2 + ), and hetarynium ions (2-pyridyl, 2-pyrrolyl cations, and their analogues) . As a result of the multiplicity of suitable reactant ions and neutrals, various heterocycle ionic systems are successfully generated via polar transacetalizations.…”

Untitled

“…The ion-molecule transacetalization reactions of heterocumulenes of the type [ONCNXNCNO] + (X = N and CH) have been studied using multistage mass spectrometry experiments. 182 Stepwise double transacetalization with cyclic acetals or ketals is observed and results in very stable charge-delocalized ions as shown in eqn. (42).…”

10 Gas phase organic ion–molecule reaction chemistry

“…used an FT-ICR and an ion trap mass spectrometer to study the ion^molecule reactions observed in the ionization of organophosphorus esters (trimethyl phosphite, triethyl phosphite, dimethyl phosphonate, trimethyl phosphate and 2,2-dichlorovinyl dimethyl phosphate). The phosphonates and phosphates mainly give proton-bound dimers and the phosphites give condensation products of the general formula [(RO) 3 P (RO) 2 P] .Eberlin and co-workers91 have used pentaquadrupole (QqQqQ) mass spectrometry to explore the reactions of SF n (n 1^5) ions with benzene, acetonitrile, and pyridine. With benzene, SF reacts by an electrophilic substitution pathway to give benzenesulfenyl £uoride, C 6 H 5 ^SF .…”