Acceleration of Acetal Hydrolysis by Remote Alkoxy Groups: Evidence for Electrostatic Effects on the Formation of Oxocarbenium Ions

Garcia, Angie; Otte, Douglas A. L.; Salamant, Walter A.; Sanzone, Jillian R.; Woerpel, K. A.

doi:10.1002/ange.201410043

Cited by 12 publications

(4 citation statements)

References 30 publications

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“…[26] An epoxide product (10 c) was isolated in 67 %y ield proceeding through two separate steps (Scheme 5b). [27] Overall, the results using this catalytic system are synthetically relevant and are comparable to the state-of-the-art in radical-based intermolecular dehydrogenation reactions.…”

Section: Resultssupporting

confidence: 55%

Ruthenium‐Catalyzed Dehydrogenation Through an Intermolecular Hydrogen Atom Transfer Mechanism

et al. 2021

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The direct dehydrogenation of alkanes is among the most efficient ways to access valuable alkene products. Although several catalysts have been designed to promote this transformation, they have unfortunately found limited applications in fine chemical synthesis. Here, we report a conceptually novel strategy for the catalytic, intermolecular dehydrogenation of alkanes using a ruthenium catalyst. The combination of a redox‐active ligand and a sterically hindered aryl radical intermediate has unleashed this novel strategy. Importantly, mechanistic investigations have been performed to provide a conceptual framework for the further development of this new catalytic dehydrogenation system.

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Section: Resultssupporting

confidence: 55%

Ruthenium‐Catalyzed Dehydrogenation Through an Intermolecular Hydrogen Atom Transfer Mechanism

et al. 2021

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“…Thus, important issues involve the possible involvement of fused and bridging ions versus that of glycosyl oxocarbenium ions and/or reactive intermediates such as glycosyl triflates in the transition state for glycosidic bond formation, with evidence presented both for, and against, dependent on the system and conditions under study. 177,178,[221][222][223][224][225][226][227][228][229] This delicate balance between stereodirecting participation and alternative mechanisms is a prominent feature of the involvement of esters in glycosylation and apparent from the comparison of a recent study on 1,2-trans-glycosylation directed by the presence of 2-O-alkoxymethyl methyl groups, 230 and one of the many instances of intramolecular aglycone delivery, 231 a common strategy for 1,2-cis glycoside formation (Scheme 31). [232][233][234]…”

Section: Participation By Other Functional Groupsmentioning

confidence: 99%

Mechanisms of Stereodirecting Participation and Ester Migration from Near and Far in Glycosylation and Related Reactions

et al. 2020

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This review is the counterpart of a 2018 Chemical Reviews article that examined the mechanisms of chemical glycosylation in the absence of stereodirecting participation. Attention is now turned to a critical review of the evidence in support of stereodirecting participation in glycosylation reactions by esters from either the vicinal or more remote positions. As participation by esters is often accompanied by ester migration, the mechanism(s) of migration are also reviewed. Esters are central to the entire review, which accordingly opens with an overview of their structure and their influence on the conformations of six-membered rings. Next the structure and relative energetics of dioxacarbeniun ions are covered with emphasis on the influence of ring size. The existing kinetic evidence for participation is then presented followed an overview of the various intermediates either isolated or characterized spectroscopically. The evidence supporting participation from remote or distal positions is critically examined and alternative hypotheses for the stereodirecting effect of such esters is presented. The mechanisms of ester migration are first examined from the perspective of glycosylation reactions, and then more broadly in the context of partially acylated polyols.

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“…110–112 Our studies of reactions of alkoxy-substituted acetals showed that the presence of an alkoxy group, which is inductively electron-withdrawing, can accelerate acetal hydrolysis if it can approach the developing carbocationic carbon atom (Scheme 54 ). 113 114 The rate acceleration trends in hydrolysis were also observed for solvolysis of tosylates (Scheme 55 ). The acceleration is higher than one sees with acyloxy groups, suggesting that alkoxy groups are more participating, likely because their inductive-withdrawing ability is lower.…”

Section: Neighboring-group Participation Is Not As Simple As It Seemsmentioning

confidence: 84%

Acetal Substitution Reactions: Stereoelectronic Effects, Conformational Analysis, Reactivity vs Selectivity, and Neighboring-Group Participation

Woerpel,

Chun,

Luu

2024

Synlett

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Acetal substitution reactions can proceed by a number of mechanisms, but oxocarbenium ion intermediates are involved in many of these reactions. Our research has focused on understanding the conformational preferences, structures, and reactions of these intermediates. This account summarizes our observations that electrostatic effects play a significant role in defining the preferred conformations, and that torsional effects determine how those intermediates react. Neighboring-group effects are not as straightforward as they might seem, considering that oxocarbenium ion intermediates are in equilibrium with structures that involve stabilization by a nearby substituent.1 Introduction2 Unexpected Stereoselectivities3 Determining Conformational Preferences of Oxocarbenium Ions4 Structures of Carbocations by NMR Spectroscopy and X-ray Crystallography5 Stereoelectronic Models for Reactions Involving Other Oxocarbenium Ions6 Stereoselectivity and Reactivity: When They Correlate, When They Do Not7 Neighboring–Group Participation Is Not as Simple as It Seems8 What Is True for Carbocations Is True for Carbonyl Compounds9 Stereoelectronic and Torsional Effects in Reactions of Enolates10 Summary of Expected Selectivities for Reactions of Cyclic Acetals11 Conclusion

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Acceleration of Acetal Hydrolysis by Remote Alkoxy Groups: Evidence for Electrostatic Effects on the Formation of Oxocarbenium Ions

Cited by 12 publications

References 30 publications

Ruthenium‐Catalyzed Dehydrogenation Through an Intermolecular Hydrogen Atom Transfer Mechanism

Ruthenium‐Catalyzed Dehydrogenation Through an Intermolecular Hydrogen Atom Transfer Mechanism

Mechanisms of Stereodirecting Participation and Ester Migration from Near and Far in Glycosylation and Related Reactions

Acetal Substitution Reactions: Stereoelectronic Effects, Conformational Analysis, Reactivity vs Selectivity, and Neighboring-Group Participation

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