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Showing 1 to 20 of 22 for “"Electrophilic substitution"”.
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Enantioselective Alpha-Lithiation of N-Boc-N-(p-Methoxyphenyl)allylamines Mediated by (--)-Sparteine
… in the presence of (-)-sparteine followed by electrophilic substitution provides enecarbamates with configurations opposite to that obtained by the deprotonation sequence. The enecarbamates can be hydrolyzed to aldehydes or reduced to amines, and therefore provide facile entry into chiral …
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Enantioselective lateral lithiation-substitution of o-ethyl- and o-benzyl-N-pivaloylanilines: Studies of a pathway of stereoinformation transfer
… to generate a dilithio intermediate. Electrophilic substitution of the organolithium in the presence of ($-$)-sparteine provides the products with enantiomeric excesses close to 80% for reactions with most electrophiles. The absolute configuration at the benzylic carbon is the same …
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Studies of alpha-lithioamine synthetic equivalents: I. Elaboration of primary amines. II. Detection of an intermediate in the lithiation of a benzylic urea
Reagents for the $\alpha$-substitution of N-Boc-benzylamine and N-Boc-allylamine have been developed via dilithiation and electrophilic substitution. Discussion of the specific conditions employed to accomplish these transformations is presented, as well as mechanistic speculation. Dilithiation and …
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The synthesis and reactivity of 7-azaindolizines.
… ,2-a:2,1-c]pyrazine system. A number of electrophilic substitution reactions occurred at C-3 position. Nucleophilic replacement of chlorine by methoxide and amino from 8-chloro-2-methyl-7-azaindolizine occurred readily. A number of simple alkyl, aryl, and carboethoxy substituted …
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Chemical and Mechanistic Studies of Alpha' Lithio Amides
The lithiation and electrophilic substitution of the allyl amides, N-allyl-N-methyl-2-ethyl-methylbutanamide (76), 1,2,5,6-tetrahydropyridinyl-2-ethyl-2-methylbutanamide (77), 3-methylene-2-ethyl-2-methylbutanamide (78) and 5-tert-butyl-1,2,5,6-tetrahydropyridinyl-2-ethyl-2-methylbutanamide (79) is …
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(--)-Sparteine Mediated Asymmetric Synthesis Through Conjugate Addition of Allylic and Benzylic Organolithium Species: Development of a Methodology and Its Application Toward a Total Synthesis
… The enantioenriched products that arise on electrophilic substitution with N-protected pyridones are precursors to piperidine alkaloids. Moreover, this reaction has been applied as the key step in the total synthesis of an immediate precursor to the indolizidine alkaloid castanospermine.
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Remote Lithiations of Carboxamides: The Manifestation of a Post-Complexation Proximity Effect (Homoenolate)
… products. In the case of 217, metalation and electrophilic substitution occurs at a (beta) secondary carbon atom. The allylic alkyllithium generated undergoes electrophilic at the (beta) or (delta) position. Lithiation and substitution at the (gamma) position occurs upon treatment of …
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A Contribution to the Chemistry of 1,2,3-BENZOTHIADIAZOLE
… benzene ring is used to explain the products of electrophilic substitution. Much of the work described in this thesis has already been published 1,2 and the remainder is largely incorporated in a third paper. The latter has recently been recommended for publication in the Journal of The Chemical …
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Development of a synthetic route to aminofluorohexenones as precursors for novel caspase inhibitors
… adjacent to nitrogen, that focuses on an electrophilic substitution reaction based on charge affinity inversion of customary amine reactivity. The second part of the synthetic strategy involves generation of pentenoic acid analogs to be used as electrophiles in the overall construction of …
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The Chlorination of Pharmaceuticals and Other Phenolic Compounds in the Presence of Iodide
… rate over-simplified the analysis of halogen substitution reactions. Free chlorine reaction rate constant values were updated from the literature since the mechanism for electrophilic substitution was found to be different than stated in currently published literature. The involvement of …
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Chiral phosphonyl and thiophosphonyl carbanions in asymmetric alkylation and olefination reactions
… underwent smooth electrophilic substitution with excellent diastereoselectivity in both l- and u-stereoisomers, which allowed the preparation of scalemic phosphonic acids and phosphonates with three $\alpha$-substitution patterns (aryl, alkyl, and alkoxy). Synthesis …
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Synthesis of ferrocenyl and 1-methylpyrrolyl bisphophines via electrophilic addition and substitution reactions of tungsten-coordinated phosphenium ions and phosphine triflates
… bisphosphine complexes were synthesized using electrophilic substitution reactions of tungsten pentcarbonyl-coordinated phosphenium ions [W(CO)5(PRRʹ)]+, phosphine triflates [W(CO)5{PRRʹ(OSO2CF3)}], [W(CO)5{PRCl(OSO2CF3)}] and protonated amino phosphine [W(CO)5{PCl2NH(Et)2}]+ (38) with …
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Preparation and Properties of Azetidine-2-Ones
… by ring opening of the azetidinone and electrophilic substitution of the intermediate into the aromatic ring of the solvent. Anisole has also been shown to undergo this reaction. 4,3,3,4-Tetraphenylazetidine-2-one also undergoes rearrangement in the presence of boron trifluoride etherate …
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The synthesis and reactivity of 6- and 8-azaindolizines.
… at C-3 and then at C-1. A number of other electrophilic substitution reactions on 2,7-dimethyl-8-azaindolizine also occurred at C-3. Nucleophilic replacement of chlorine by methoxide from a 5-chloro-6-azaindolizine and a 7-chloro-8-azaindolizine occurred readily. Ammonolysis and hydrolysis …
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Synthesis and properties of some 4H-1, 3, 4 benzothiadiazines /|nby Darko J. Vukov. -- 260 St. Catharines, Ont. : [s. n.],
… halogen substituent in the 7-position undergoes electrophilic attack preferentially in 5-posi tion. \fuen the 5-posi tion is occupied by a halogen atom, electrophilic substitution occurs at the 7-position of 4H-l,3,4 benzothiadiazine ring system. Substitution at the 4-nitrogen atom in 4H w l,3,4 …
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Regiospecific Synthesis of Ortho Substituted Phenols
<p>Phenol is highly reactive toward electrophilic aromatic 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 …
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Formation of 2,5-trans-tetrahydrofuran-3-one application towards the synthesis of natural products
… This activated intermediate can then undergo the electrophilic substitution. This method led to the trans cyclisation product in up to 40:1 ratio. In order to increase the level of diastereocontrol our group have investigated a methodology based on an intramolecular tandem carbenoid insertion and …
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Searching for potential markers for monitoring the presence of opiates in urine exposed to oxidising adulterants
… 2-nitro analogues was hypothesised to follow an electrophilic substitution reaction. The production of codeinone was suggested to be initiated by the chromium (VI) complex found in PCC. It was discovered that both nitrite and PCC caused a decrease in the response of the CEDIA 6-AM and opiate …
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The Use of Functionalized Zirconocenes as Precursors to Silica-Supported Zirconocene Olefin Polymerization Catalysts
… to obtain substituents bearing more than one electrophilic bond. The reactivities of Me3Sn and Ph2MeSi substituents were explored in detail. (Me3Sn)2C5H4 combined with CpZrCl3 in toluene to afford (h5-Me3Sn-C5H4)CpZrCl2 (A). Reactions of A with electrophiles (E-X = Cl2B-Cl, I-Cl, and I-I) …
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