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Showing 1 to 20 of 32 for “"directing group"”.
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Directing group-free endo-selective epoxide-opening cascades
… are strongly disfavored, and non-natural directing groups must be covalently attached to each epoxide to overcome this inherent bias. We report herein a general method for directing group-free cascades that also supports the postulated biosynthesis. The two salient aspects of this strategy …
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C(sp2)–H Functionalizations Employing 2-Aminophenyl-1H-pyrazole as a New Removable Directing Group
… was discovered as a novel removable bidentate directing group for copper-mediated aerobic oxidative C(sp2)–H bond amidation and sulfonamidation bearing a wide range of sulfonamides, When Cu(OAc)2 was employed as the copper source, 1,1,3,3-tetramethylguanidine (TMG) as an organic base, the …
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The development of directing group enabled hydroamination strategies to access to 1,2-, 1,3-, and 1,4- diamines with high levels of regio-, chemo-, and stereoselectivity
… goal of for many transition-metal catalysis groups, including ours. We have chosen to approach this from the vantage of a hydroamination reaction of olefins, as olefins and amines are both readily accessible. This reaction has the potential to be entirely atom-economical, as well as modular. …
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Synthetic and Mechanistic Studies of Carbamate-Directed Lithiation Reactions: (1) Assymetric Deprotonation of N-Boc Indolines. (2) the Relationship Between Reactivity and Directing Group Orientation
… demonstrate that the position of the carbonyl group with respect to the proton removed in a carbamate-directed lithiation affects the efficiency of the reaction as well as the configurational stability of the organolithium intermediate.
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The acidic sulfonimidation of aryl–oxazolines and the electrophilic fluorination of aryl–oxazolines
<p>Aryl oxazolines have been employed as directing groups for several different coupling reactions. In the exploration of using phenyl oxazoline as a directing group for electrophilic fluorination, it was discovered that acidic sulfonimide nucleophiles including dibenzenesulfonimide, …
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INVESTIGATIONS IN IRON, COPPER, AND PALLADIUM –CATALYZED C-H BOND FUNCTIONALIZATION
… with simple amines using 8-aminoquinoline directing group and a copper catalyst. Sulfenylation and amination of -C-H bonds of benzyl amine derivatives using picolinic acid auxiliary were also demonstrated. Broad substrate scope, high regioselectivity, and good functional group tolerance …
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Synthesis, structures and studies of organoiron compounds
… the (η⁵-cyclopentadienyl) iron (II) dicarbonyl group by variable temperature ¹H NMR spectroscopic studies on cis-4-phenyl-1-(η⁵-cyclopentadienyl) iron (II) dicarbonyl cyclohexane. This is the first determination of the A value of a group with a transition metal directly attached to a cyclohexane …
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Alpha-lithioamine synthetic equivalents from N-Boc secondary amines: Piperideine, pyrrolidine, and perhydroazepine
The tert-butoxycarbonyl (Boc) group has been shown to be an excellent lithiation directing group for the $\alpha\sp\prime$-metalation of carbamates from unactivated cyclic secondary amines; piperidine, pyrrolidine, and perhydroazepine to provide $\alpha$-lithioamine synthetic equivalents. The Boc …
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Studies on directed lithiation: 1. Reactivity studies on alkoxide-directed lithiation reactions. 2. NMR spectroscopic characterization of the solution structure of an asymmetric lithiation reagent
… favorable geometric orientation of the alkoxide directing group with respect to the proton being removed. The second lithiation is the only example of a bis-cyclopropyl compound undergoing dilithiation and appears to be the result of a complex-induced proximity effect.
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Novel syntheses by directed lithiations of N-Boc benzylamines and cyclopropylamines
… has been achieved successfully. Also, the N-Boc group was used as an activating and directing group for the $\alpha$ and $\beta$ lithiation-substitution of cyclopropanes. Extension of this chemistry to syntheses of highly functionalized cyclopentane by (3 + 2) cycloaddition and asymmetric …
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Slow-release cross-coupling and an advanced method for β-glycosylation: methods stimulated by amphotericin B
… products both within and outside our research group. To overcome the challenging 1,2-cis glycosidic bond found in AmB a mycosamine sugar donor synthesis was developed incorporating a new directing group for neighboring group participation. The use of this new directing group enabled efficient …
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Regiospecific Synthesis of Ortho Substituted Phenols
… substitution. By this general approach, many groups can be appended to the ring, via halogenation, acylation, sulfonation, and other processes. Phenol contains the hydroxyl group (–OH), which is a strongly activating ortho/para directing group in aromatic electrophilic substitution (AES). AES …
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1. The Endocyclic Restriction Test: Oxygen Transfer From N-Sulfonyl Oxaziridines to Alkenes and Fluorine From N-Fluorosultams to Carbanions. 2. Intra- and Intermolecular Kinetic Isotope Effects in Directed Lithiations
… base coordinates to the heteroatom of the directing group prior to the deprotonation step. These experiments underscore the inability of this method to quantify large isotope effects and the need to access the error of the measurements when comparing intra- and intermolecular kinetic …
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A hydrogen bonding ortho-directing effect for the iridium catalyzed borylation of NH(t-BOC) aromatics
… of regioselective activation and high functional group tolerance have been considerably praised. Most aromatic substituents, such as alkyl, esters, amides, nitriles, amines, protected phenols and others act as steric obstacles for the iridium catalyst to avoid. This avoidance of appending groups …
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Nickel-catalyzed reductive coupling reactions : application to the total syntheses of pumiliotoxins 209F and 251D
… exclusively endo products without the use of a directing group on the alkyne. The synthesis of the reductive coupling precursors involved a diastereoselective sulfur ylide epoxidation of a proline-derived methyl ketone, where the choice of sulfonium salt conferred a major effect on the …
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Nickel-catalyzed asymmetric cross-couplings of secondary allylic chlorides and planar-chiral compounds in asymmetric synthesis
… functionalization of ferrocene using a chiral directing group enables the formation of a number of amines in enantiopure form. These catalysts are tested as several asymmetric catalysts.
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Carbon−Hydrogen Bond Functionalization using Removable Monodentate Directing Groups
… was employed as a mono-dentate directing group for palladium-catalyzed ortho-sp2 C−H arylation with aryl iodides. The reaction shows good functional group tolerance and outstanding selectivity for mono-ortho-arylation. Ozonolysis of ortho-arylated arylpyrazoles gave acylated …
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C-H Activation of Functional Materials
… and good d.r., with many different functional groups and substitution patterns being tolerated. Further transformation of the lactam was also demonstrated, yielding pyrrolidines and functionalised lactams. Chapter 2 describes the development of a carboxylate directed C-H arylation of azulene at …
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Diastereoselective Synthesis of Planar Chiral N-Substituted Ferrocenes Derived from Epimeric Imidazolones and their Application to Asymmetric Hydrogenation of Quinolines
… ferrocene bearing a proline-derived chiral directing group and diastereoselective lithiation-electrophile quench of the pro-Sp hydrogen of the ferrocene to give planar chiral products in >95:5 dr. The auxiliary group is found to be stable to lithium bases of types RLi and R2NLi giving the …
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Zincative Functionalization of C–H Bonds Using Lithium Amide Zincate Bases
… the direct introduction of valuable functional groups improves atom economy and efficiency. However, field of direct C–H functionalization still has many challenges including regioselectivity, directing group limitations, and often harsh reaction conditions with toxic and rare transition metal …
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