Data on the structures of phosphorylated allenes (PA) and their reactions with electrophiles are ... more Data on the structures of phosphorylated allenes (PA) and their reactions with electrophiles are surveyed for the first time. It is shown that the influence of intramolecular interactions on the reactivity of the unsaturated centres is reflected in the selectivity of the reactions of PA with electrophiles. Depending on the nature of the reactants and the structure of the PA,
Efficient rehybridization at nitrogen provides a convenient conceptual framework for rationalizin... more Efficient rehybridization at nitrogen provides a convenient conceptual framework for rationalizing structural and electronic effects in substituted anilines. Computations predict that a subtle balance between hybridization and conjugation in substituted anilines is easily perturbed by remote substitution. Rehybridization correlates with electronegativity of substituents as predicted by the Bent’s rule even though the substitution is not direct but mediated by an aromatic system. Use of the σ− Hammett parameters significantly improves the description of substituent effects. Limitations of X-ray crystallography in studies of subtle electronic structure effects are shown through comparison of computational geometries with crystallographic data which illustrates how supramolecular forces associated with the crystal packing mask intrinsic electronic preferences.
... Denis S. Baranova, Sergei F. Vasilevsky*a, Brian Goldb and Igor V. Alabugin*b. a Institute of... more ... Denis S. Baranova, Sergei F. Vasilevsky*a, Brian Goldb and Igor V. Alabugin*b. a Institute of Chemical Kinetics and ... 1034 CrossRef CAS Search PubMed ; (d) Electrophilic cyclizations: AA Stepanov, LM Gornostaev, SF Vasilevsky, EV Arnold, VI Mamatyuk, DS Fadeev, B. Gold ...
Journal of the American Chemical Society, Jan 23, 2015
Chemoselective interaction of aromatic enynes with Bu3Sn radicals can be harnessed for selective ... more Chemoselective interaction of aromatic enynes with Bu3Sn radicals can be harnessed for selective cascade transformations yielding either Sn-substituted naphthalenes or Sn-indenes. Depending on the substitution at the alkene terminus, the initial regioselective 5-exo-trig cyclizations can be intercepted at the 5-exo stage either via hydrogen atom abstraction (HAA) or C-S bond scission, or allowed to proceed further to the formal 6-endo products via homoallylic ring expansion. Aromatization of the latter occurs via β-C-C bond scission which is facilitated by 2c,3e-Through-Bond (TB) interactions, a new stereoelectronic effect in radical chemistry. The combination of formal 6-endo-trig cyclization with stereoelectronically optimized fragmentation allows the use of alkenes as synthetic equivalents of alkynes and opens a convenient route to α-Sn-substituted naphthalenes, a unique launching platform for the preparation of extended polyaromatics.
Our recent work has provided an alternative strategy for acceleration of azide/alkyne cycloadditi... more Our recent work has provided an alternative strategy for acceleration of azide/alkyne cycloadditions via selective transition state (TS) stabilization. Optimization of hyperconjugative assistance, provided by the antiperiplanar arrangement of propargylic σ-acceptors relative to the forming bonds, is predicted to relieve strain in cyclooctynes while providing large acceleration to the cycloaddition. The present work investigates this strategy in alkynyl crown ethers, where propargylic C-O bonds contained within the macrocycle are constrained close to proper alignment for hyperconjugative assistance. Preorganization of σ-acceptors into the optimal arrangement for hyperconjugative interactions may alleviate a portion of the entropic penalty for reaching the TS. Optimal alignment can be reinforced, and transition-state stabilization can be further amplified by binding positively charged ions to the crown ether core, highlighting the potential for applications in ion sensing.
Previously, we reported the design and properties of alkyne C-lysine conjugates, a powerful and t... more Previously, we reported the design and properties of alkyne C-lysine conjugates, a powerful and tunable family of DNA cleaving reagents. We also reported that, upon photoactivation, these molecules are capable of inducing cancer cells death. To prove that the cell death stems from DNA cleavage by the conjugates, we investigated intracellular DNA damage induced by these molecules in LNCap cancer cells using single cell gel electrophoresis (SCGE) assays. The observation of highly efficient DNA damage confirmed that lysine acetylene conjugate is capable of cleaving the densely compacted intracellular DNA. This result provides a key mechanistic link between efficient DNA cleavage and cytotoxicity towards cancer cells for this family of light-activated anticancer agents.
This study reports a new photochemical cyclization of tetrafluoropyridinyl (TFP)-substituted ened... more This study reports a new photochemical cyclization of tetrafluoropyridinyl (TFP)-substituted enediynes that is accompanied with four formal hydrogen-atom abstractions from organic substrates and is mechanistically different from the Bergman cyclization.
Data on the structures of phosphorylated allenes (PA) and their reactions with electrophiles are ... more Data on the structures of phosphorylated allenes (PA) and their reactions with electrophiles are surveyed for the first time. It is shown that the influence of intramolecular interactions on the reactivity of the unsaturated centres is reflected in the selectivity of the reactions of PA with electrophiles. Depending on the nature of the reactants and the structure of the PA,
Efficient rehybridization at nitrogen provides a convenient conceptual framework for rationalizin... more Efficient rehybridization at nitrogen provides a convenient conceptual framework for rationalizing structural and electronic effects in substituted anilines. Computations predict that a subtle balance between hybridization and conjugation in substituted anilines is easily perturbed by remote substitution. Rehybridization correlates with electronegativity of substituents as predicted by the Bent’s rule even though the substitution is not direct but mediated by an aromatic system. Use of the σ− Hammett parameters significantly improves the description of substituent effects. Limitations of X-ray crystallography in studies of subtle electronic structure effects are shown through comparison of computational geometries with crystallographic data which illustrates how supramolecular forces associated with the crystal packing mask intrinsic electronic preferences.
... Denis S. Baranova, Sergei F. Vasilevsky*a, Brian Goldb and Igor V. Alabugin*b. a Institute of... more ... Denis S. Baranova, Sergei F. Vasilevsky*a, Brian Goldb and Igor V. Alabugin*b. a Institute of Chemical Kinetics and ... 1034 CrossRef CAS Search PubMed ; (d) Electrophilic cyclizations: AA Stepanov, LM Gornostaev, SF Vasilevsky, EV Arnold, VI Mamatyuk, DS Fadeev, B. Gold ...
Journal of the American Chemical Society, Jan 23, 2015
Chemoselective interaction of aromatic enynes with Bu3Sn radicals can be harnessed for selective ... more Chemoselective interaction of aromatic enynes with Bu3Sn radicals can be harnessed for selective cascade transformations yielding either Sn-substituted naphthalenes or Sn-indenes. Depending on the substitution at the alkene terminus, the initial regioselective 5-exo-trig cyclizations can be intercepted at the 5-exo stage either via hydrogen atom abstraction (HAA) or C-S bond scission, or allowed to proceed further to the formal 6-endo products via homoallylic ring expansion. Aromatization of the latter occurs via β-C-C bond scission which is facilitated by 2c,3e-Through-Bond (TB) interactions, a new stereoelectronic effect in radical chemistry. The combination of formal 6-endo-trig cyclization with stereoelectronically optimized fragmentation allows the use of alkenes as synthetic equivalents of alkynes and opens a convenient route to α-Sn-substituted naphthalenes, a unique launching platform for the preparation of extended polyaromatics.
Our recent work has provided an alternative strategy for acceleration of azide/alkyne cycloadditi... more Our recent work has provided an alternative strategy for acceleration of azide/alkyne cycloadditions via selective transition state (TS) stabilization. Optimization of hyperconjugative assistance, provided by the antiperiplanar arrangement of propargylic σ-acceptors relative to the forming bonds, is predicted to relieve strain in cyclooctynes while providing large acceleration to the cycloaddition. The present work investigates this strategy in alkynyl crown ethers, where propargylic C-O bonds contained within the macrocycle are constrained close to proper alignment for hyperconjugative assistance. Preorganization of σ-acceptors into the optimal arrangement for hyperconjugative interactions may alleviate a portion of the entropic penalty for reaching the TS. Optimal alignment can be reinforced, and transition-state stabilization can be further amplified by binding positively charged ions to the crown ether core, highlighting the potential for applications in ion sensing.
Previously, we reported the design and properties of alkyne C-lysine conjugates, a powerful and t... more Previously, we reported the design and properties of alkyne C-lysine conjugates, a powerful and tunable family of DNA cleaving reagents. We also reported that, upon photoactivation, these molecules are capable of inducing cancer cells death. To prove that the cell death stems from DNA cleavage by the conjugates, we investigated intracellular DNA damage induced by these molecules in LNCap cancer cells using single cell gel electrophoresis (SCGE) assays. The observation of highly efficient DNA damage confirmed that lysine acetylene conjugate is capable of cleaving the densely compacted intracellular DNA. This result provides a key mechanistic link between efficient DNA cleavage and cytotoxicity towards cancer cells for this family of light-activated anticancer agents.
This study reports a new photochemical cyclization of tetrafluoropyridinyl (TFP)-substituted ened... more This study reports a new photochemical cyclization of tetrafluoropyridinyl (TFP)-substituted enediynes that is accompanied with four formal hydrogen-atom abstractions from organic substrates and is mechanistically different from the Bergman cyclization.
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