Use of Borinium Ions as Probes of Steric Effects in Gas-phase Ion-Molecule Complexes

Isbell, John; Brodbelt, Jennifer S.

doi:10.1002/(sici)1097-0231(199608)10:11<1418::aid-rcm685>3.0.co;2-f

Cited by 11 publications

(5 citation statements)

References 2 publications

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“…Brodbelt and co‐workers have used an equilibrium method, which looks at the position of equilibrium or the rate of cation transfer between two bases, to determine gas‐phase affinities of several substituted pyridines for B(OMe) BMe 2 + 66. Results showed a general correlation with gas‐phase basicities, with the differences in binding affinities for dimethyl‐ and methyl‐substituted pyridines consistent with the differences in the analogous gas‐phase basicities upon comparison of species with either no ortho ‐substitution (e.g.…”

Section: Reactivity Of Borocationsmentioning

confidence: 99%

Borinium, Borenium, and Boronium Ions: Synthesis, Reactivity, and Applications

2005

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Boron cations are elusive and highly electrophilic species that play a key role in the chemistry of boron. Despite early interest in the chemistry of boron cations, until recently they have largely remained chemical curiosities. However, hints at harnessing their potential as potent electrophiles have begun to appear and developments in weakly coordinating anion technology suggest that this is an area of research that is ripe for exploration. It has been nearly 20 years since the last major review on boron cations; herein we summarize the progress in the area since that time.

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Section: Reactivity Of Borocationsmentioning

confidence: 99%

Borinium, Borenium, and Boronium Ions: Synthesis, Reactivity, and Applications

2005

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“…26 An equilibrium study on the binding of CH 3 OB + OCH 3 to the substituted pyridines also established that association is sensitive to the substituents near the site of ion attachment. 27 These studies demonstrate that the binding energy of CH 3 OB + OCH 3 to neutral ligands is controlled by both steric and electronic effects.…”

Section: Introductionmentioning

confidence: 95%

Synthesis of B- and P-Heterocycles by Reaction of Cyclic Acetals and Ketals with Borinium and Phosphonium Ions

et al. 1999

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Tricoordinated cyclic boron cations result from gas-phase ion/molecule reactions of dicoordinated borinium ions with neutral acetals and ketals and thiazolidine. The reaction, which proceeds via initial cationic binding to a heteroatom followed by a consecutive ring-opening and ring-reclosing process, resembles the Eberlin transacetalization of acylium ions (Eberlin, M. N.; Cooks, R. G. Org. Mass Spectrom. 1993, 28, 679). The cyclic structure of the tricoordinated boron cation is demonstrated by tandem mass spectrometry and further confirmed by comparison with authentic cyclic tricoordinated boron cations. The five-membered cyclic boron cations dissociate by ethylene oxide loss to thus reform the reactant-dicoordinated borinium ion; the six-membered boron cations fragment instead by ethylene loss. Consistent with the proposed mechanism, the ion/molecule reaction efficiency falls in the order CH(3)OB(+)C(2)H(5) > CH(3)OB(+)OCH(3) >> CH(3)B(+)CH(3); i.e., the higher the nucleophilicity of the borinium ion, the higher the reaction efficiency. A potential energy surface is calculated for the reaction of CH(3)OB(+)OCH(3) with 2-methyl-1,3-dioxolane, and the reaction is found to be 43.3 kcal/mol exothermic due to initial formation of a strong B-O bond. The analogous reactivity displayed by phosphonium ions is also investigated by both experiment and ab initio calculations. In contrast to the borinium ions, the phosphonium ions exhibit higher regioselectivity for sulfur compared to nitrogen and oxygen. Finally, the present findings indicate that the reaction exothermicity and the regioselectivity are controlled by both the Lewis acidity of the reactant cations and the leaving ability of the released neutrals in the rate-limiting nucleophilic-induced recyclization step.

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“…Borinium ions also attack long‐chain aldehydes or ketones to induce CO and C—C cleavages 20. On the basis of their stereospecific reactivity toward diols and saccharides, borinium ions have been used to distinguish diastereomers21 and have been proposed for the gas‐phase structural characterization of organic and biologically active diols and polyols 22…”

Section: Introductionmentioning

confidence: 99%

Synthesis of B, N, O-containing heterocycles via reaction of an aminoborinium ion with cyclic acetals and ketals

2000

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Dimethylaminoborinium ion [(CH 3 ) 2 NB Y N(CH 3 ) 2 ] undergoes gas-phase Eberlin reactions (Eberlin MN, Cooks RG. Org. Mass. Spectrom. 1993; 28: 679) with neutral cyclic acetals and ketals. Analogously to trans-acetalization in the condensed phase, this reaction involves initial nucleophilic addition at the borinium cation by the acetal or ketal, followed by a ring-opening/recyclization process with concomitant loss of a neutral carbonyl compound and formation of an ionic B, N, O-containing heterocyclic product. The cyclic nature of the product is strongly suggested by multiple-stage mass spectrometry experiments. The reaction gives relatively higher yields than the corresponding acylium, phosphonium and silylium ion reactions and shows larger influences due to the position of the substituent group in 1,3-dioxolanes. Electronic and steric factors have opposite effects on the reaction efficiency, which is consistent with the proposed mechanism.

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Use of Borinium Ions as Probes of Steric Effects in Gas-phase Ion-Molecule Complexes

Cited by 11 publications

References 2 publications

Borinium, Borenium, and Boronium Ions: Synthesis, Reactivity, and Applications

Borinium, Borenium, and Boronium Ions: Synthesis, Reactivity, and Applications

Synthesis of B- and P-Heterocycles by Reaction of Cyclic Acetals and Ketals with Borinium and Phosphonium Ions

Synthesis of B, N, O-containing heterocycles via reaction of an aminoborinium ion with cyclic acetals and ketals

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