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Showing 1 to 20 of 28 for “"Sparteine"”.
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The Desaturation of Sparteine and Related Model Amines
Made available in DSpace on 2014-12-05T19:36:08Z (GMT). No. of bitstreams: 1 0010555.pdf: 7451931 bytes, checksum: a2af69da6b5ce3dee864f54f168d4391 (MD5) Previous issue date: 1954
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Asymmetric Syntheses With (-)-Sparteine-Complexed Benzylic and Allylic Organolithium Reagents
… with n -BuLi/(-)-sparteine was investigated. Kinetic resolution in conjugate addition reactions with alpha,beta-unsaturated lactones proceed with retention of configuration to provide 1,4-addition products with three contiguous stereogenic centers with high …
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Enantioselective Alpha-Lithiation of N-Boc-N-(p-Methoxyphenyl)allylamines Mediated by (--)-Sparteine
… allylic stannanes 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 …
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Asymmetric Lithiation-Substitution Sequences of Functionalized Allylic and Benzylic Amines Mediated by (-)-Sparteine
Modification of the allyl amine with selected substituents at the beta and gamma-positions allowed for an examination of yields, product distributions, enantioenrichments, mechanistic understanding and synthetic applications. With an extended allyl amine, enantioenriched diene products were …
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Mechanistic Investigations and Synthetic Development of (-)-Sparteine Mediated Asymmetric Benzylic Lithiation-Substitution Reactions of Secondary Amides
The synthetic utility of the lithiation-substitutions of N-(2-phenethyl)isobutyramide has also been investigated. Enantioenriched substituted products have been carried forward in the synthesis of 1,4-disubstituted dihydro- and tetrahydroisoquinolines. Variation of either substituent is convenient …
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Synthesis of Heterometallic nitridoruthenium(VI) Complexes With Nickel, Palladium, or Platinum: New Catalysts for the Aerobic Oxidation of Alcohols
… and limitations of [PPh4][Ru(N)Me2(mu-O) 2Pd((-)-sparteine)] as a catalytic aerobic oxidant of organic alcohols is explored. The complex [PPh4][Ru(N)Me2(mu2 -O)2Pd((-)-sparteine)] oxidizes aryl and allyl alcohols to their corresponding aldehydes. The complex also catalytically rearranges allylic …
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(-)-Sparteine Mediated Lithiation of N-Boc-N-P-(methoxyphenyl) Allylic Amines and Conjugate Addition to Nitroalkenes: Scope, Reaction Pathway, and Synthetic Applications
The enecarbamate products of the conjugate additions may also be easily elaborated to enantioenriched functionalized cyclopentanoids. Hydrolysis of the enecarbamates followed by intramolecular nitro-aldol cyclization and dehydration provides substituted nitrocyclopentenes that were converted to …
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Chiral Homoenolate Synthetic Equivalents: Mechanistic, Structural, and Kinetic Investigations
… by n-BuLi/(-)-sparteine was examined kinetically by means of in situ infrared spectroscopy. The reaction is first order in allylic amine and zero-order in 1:1 base/ligand complex. When the relative concentrations of n-BuLi and (-)-sparteine are not held constant, …
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Zinc polysulfides as precursors to zinc sulfide and as group transfer reagents
… and ($-$)-sparteine to afford $\rm ZnS\sb6$(TEEDA) and $\rm ZnS\sb6\{(-)$-sparteine$\};$ these complexes can not be prepared by the reaction of sulfur and zinc dust in TEEDA or ($-$)-sparteine. Optical and reactivity studies showed that MeIm, but not …
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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 synthetic utility of the methodology is demonstrated with the synthesis of diastereo-, and enantiomerically pure 2,3,4-trisubstituted gamma-lactams in high yield. In addition, conjugate addition of the allylic organolithium species with N-protected 4-pyridones provides high yields of the …
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New insights into homo- and heterometallic alkali metal amide chemistry
… Focusing on introducing the chiral diamines (⁻)-sparteine and N,N,Nʹ,Nʹ-(1R,2R)-tetramethylcyclohexane-1,2-diamine [(R,R)-TMCDA] into the molecular framework of bimetallic alkali metal zinc reagents, three bis(alkyl)amido sodium zincates were successfully prepared and characterised - two of the …
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Intermolecular and intramolecular asymmetric induction at the beta-benzylic position of carboxamides in directed lithiation-substitution sequences
… been achieved intermolecularly by using ($-$)-sparteine as the external chiral ligand and intramolecularly by using $\alpha$-methylbenzylamine as the covalently attached chiral auxiliary.
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Studies in asymmetric synthesis: I. the asymmetric α-alkylation of N,N-dimethylhydrazones II. the asymmetric aldol-Tishchenko reaction of (S)-tert-butanesulfinyl imines for the introduction of 2, 3, 4 and 5 new chiral centres in one pot
… synthetic equivalents and the chiral diamine sparteine. The first section of this thesis outlines efforts to further expand the scope of this methodology to include more diverse and challenging electrophiles. As a result, a number of synthetically useful ketones were prepared. Investigations …
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Enantioselective lateral lithiation-substitution of o-ethyl- and o-benzyl-N-pivaloylanilines: Studies of a pathway of stereoinformation transfer
… 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 regardless of whether stannyl or stannyl chlorides, alkyl halides, or …
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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
… has been achieved, and use of sec-BuLi/(-)sparteine as the base provided the corresponding products with up to 57% enantiomeric excess. Lithiation of N-tert-butyl-N-benzyl carbamates resulted in rearrangement to phenylglycine derivatives. These related investigations are also discussed.
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Mechanistic studies of asymmetric induction at benzylic centers of organolithium species
… in the presence of the chiral ligand (${-}$)-sparteine to generate their benzyllithium intermediates, which are subsequently reacted with electrophiles to yield highly enantioenriched products. For N-benzyl-N-Boc-N-3-chloropropyl amine, the electrophile is a part of the substrate, so the …
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Novel syntheses by directed lithiations of N-Boc benzylamines and cyclopropylamines
… N-Boc secondary amines using RLi/(-)-sparteine. Extension of this chemistry to asymmetric syntheses of both enantiomers of primary $\alpha$-substituted benzylamines and $\alpha,\alpha$-disubstituted benzylamines has been achieved successfully. Also, the N-Boc group was used as an …
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New lithiation methodologies to 2-substituted nitrogen heterocycles
… ether using s-BuLi and the diamines TMEDA, (–)-sparteine, or the (+)-sparteine surrogate. Chapter 3 describes the expansion of a previously reported two-ligand catalytic lithiation-trapping procedure for N-Boc pyrrolidine, discussing the optimisation of catalytic lithiation conditions, the use …
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Synthesis of P-Stereogenic Bisphosphine Ligands: Application as Hemi-labile Ligands in the Asymmetric Pauson-Khand Reaction
… or a phosphine borane using alkyllithium/()-sparteine complexes, trapping with Ph2PCl or t-Bu2PCl and treatment with BH3•Me2S or sulfur. This gave P-stereogenic bisphosphines. To afford highly enantioenriched ligands, the bisphosphines were recrystallised to increase the enantiomeric ratio up …
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