- Photochemical Strain-Release-Driven Cyclobutylation of C(sp3)-Centered Radicals
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A new photoredox-catalyzed decarboxylative radical addition approach to functionalized cyclobutanes is described. The reaction involves an unprecedented formal Giese-type addition of C(sp3)-centered radicals to highly strained bicyclo[1.1.0]but
- Ernouf, Guillaume,Chirkin, Egor,Rhyman, Lydia,Ramasami, Ponnadurai,Cintrat, Jean-Christophe
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p. 2618 - 2622
(2019/11/19)
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- DISULFIDE BIOCONJUGATION
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Compounds and methods are provided for one-step functionalization of disulfide bonds in proteins.
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- Unified Synthesis of 10-Oxygenated Lycopodium Alkaloids: Impact of C10-Stereochemistry on Reactivity
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The pronounced impact of the C10 stereochemistry on the successful construction of a polycyclic Lycopodium alkaloid scaffold has been explored. A wide range of reaction conditions and functionality were investigated to control a keto sulfone Michael addition to construct the C7-C12 linkage. An unexpected, overriding impact of the C10 stereochemistry in stereoselectivity and reaction rate in the Michael addition was observed. Furthermore, divergent reactivity of a conformationally accelerated, intramolecular Mannich cyclization based on the C10 stereochemistry was discovered. The successful execution of this synthetic route resulted in the total synthesis of all three known 10-oxygenated Lycopodium alkaloids: 10-hydroxylycopodine, paniculine, and deacetylpaniculine.
- Saha, Mrinmoy,Li, Xin,Collett, Nathan D.,Carter, Rich G.
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p. 5963 - 5980
(2016/07/23)
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- Diastereoselective synthesis of tetrahydrofurans via reaction of γ,δ-epoxycarbanions with aldehydes
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(Chemical Equation Presented) Hydroxymethyl-substituted tetrahydrofurans were prepared with high diastereoselectivity by reaction of the carbanion derived from 3,4-epoxybutyl phenyl sulfone with aldehydes in the presence of a mixture of lithium and potass
- Makosza, Mieczyslaw,Barbasiewicz, Michal,Krajewski, Dariusz
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p. 2945 - 2948
(2007/10/03)
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- Chiral non-racemic dihydroxysulfones via hydrolytic kinetic resolutions - Synthesis of oxacyclic ring systems using intramolecular acylation strategies
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A number of chiral non-racemic 1,2-dihydroxysulfones have been prepared in good yields and high enantiomeric excesses by hydrolytic kinetic resolution of the corresponding epoxysulfones with Jacobsen's (S,S)-salen(Co)III(OAc) catalyst. The intramolecular cyclization reactions of the acyl and ethoxycarbonyl derivatives of these dihydroxysulfones have been exploited to access a variety of functionalized chiral non-racemic cyclic ethers and lactones in good yields.
- Jin, Chunyang,Ramirez, Raina D.,Gopalan, Aravamudan S.
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p. 4747 - 4750
(2007/10/03)
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- Elimination and Addition Reactions. Part 41. Nucleophilic Eliminative Fission of Cyclopropanes: the Coiled Spring Effect of Ring Strain on Nucleofugality and its Evaluation
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Rates have been measured of sulphonyl-activated eliminative ring fissions of a series of six cyclopropanes in which the leaving group is stabilised by alkoxycarbonyl, cyano, or sulphonyl groups.The measurements allow assignment of ranks (nucleofugalities) to carbon leaving groups in systems in which the connection to the leaving group is strained by incorporation in a cyclopropane ring.The values obtained are compered with those obtained for a unstrained (acyclic) analogues.Rank enhancements of about 9(log) units are obtained; these enhancements suggests that free energies of activation for leaving-group expulsion are reduced by about 53 kJmol-1, or about 46 percent of these excess of enthalpy of the strained ring, notwithstanding the small degree of ring fission in the transition structure.The effect of phenyl substitution at the leaving group suggests that cleavage of the ring is very little advanced in the transition structure, although this is variable with the nature of the leaving-group stabilisation.This is the first direct determination of the effect of strain on nucleofugality.
- Hughes, Simon,Griffiths, Gwerydd,Stirling, Charles J. M.
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p. 1253 - 1264
(2007/10/02)
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- Preparation of Ring-Substituted (Arylsulfonyl)cyclopropanes and (Arylsulfonyl)bicyclobutanes from γ,δ-Epoxy Sulfones
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Treatment of γ,δ-epoxy sulfones 2 with n-butyllithium provides 1-(hydroxyalkyl)-2-(arylsulfonyl)cyclopropanes (3).Dehydration of the latter, when applicable, yields 1-alkenyl-2-(arylsulfonyl)cyclopropanes (5) which can be epoxidized and converted by a sec
- Gaoni, Yehiel
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p. 2564 - 2571
(2007/10/02)
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- The Contribution of Ring Strain to Nucleofugality: the First Measurement
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Comparison of eliminative ring fission in a cyclopropane and elimination in an acyclic analogue allows determination of acceleration of elimination by ring strain; a factor of at least 1011.7 has been found, the largest for any heterocyclic reaction.
- Griffiths, Gwerydd,Hughes, Simon,Stirling, Charles J. M.
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p. 236 - 237
(2007/10/02)
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- γ- and δ-epoxy sulfones. Formation of different ring-sized products upon reaction with CH3MgI or LiN2
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γ-Epoxy sulfones in which the epoxide function is terminal yield cyclopropylmethanol derivatives on reaction with methylithium or lithium diisopropylamide.In contrast, treatment of these epoxides with two equivalents of CH3MgI gives only cis-3-phenylsulfonylcyclobutanols.The cis-relationship between the OH and sulfonyl groups was proven in one instance by an X-ray stucture determination.Inernal γ-epoxy sulfones yield cyclopropylmethanols with all bases studied.All δ-epoxy sulfones studied furnished cis-3-phenylsulfonylcyclopentanols upon reaction with the Grignard reagent.These same epoxides gave either cyclopentanols or noncyclic products upon reaction with LDA; no cyclobutane ring containing products were obtained contrary to the expectations based on Stork's results with the corresponding epoxy nitriles (ref. 2).The mechanism of the Grignard-mediated reaction involves epoxide opening by iodide ion, α-sulfonyl Grignard formation, and, finally, cyclization.When LDA or CH3Li is used the products are formed by an intramolecular SN2 opening of the epoxide by an α-lithio sulfone.
- Decesare, John M.,Corbel, Bernard,Durst, Tony,Blount, John F.
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p. 1415 - 1424
(2007/10/02)
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