Enantioselective Deprotonation of Tropinone and Reactions of Tropinone Lithium Enolate

Majewski, Marek; Zheng, Guo-Zhu

doi:10.1055/s-1991-20667

Cited by 28 publications

(4 citation statements)

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“…Examination of models has shown that the conformer of (3a), in which such hydrogen bonding existed, would have a dihedral angle H2--C2--CI'--HI' of 66"; this would explain the small Jan value (Silverstein, Bassler & Morrill, 1991). Nuclear Overhauser enhancement measurements on a derivative indicated agreement with structure (3a) (Majewski & Zheng, 1991). It should be noted that even though NMR spectroscopy has been used extensively in the analysis of the structures and conformations of tropane alkaloids, some results have been questioned (Lounasmaa, 1988;Bachmann &von Philipsborn, 1972).…”

Section: Commentmentioning

confidence: 81%

“…During a study investigating the enantioselective deprotonation of ketones of Cs symmetry, we deprotonated tropinone (1) with lithium diisopropylamide and reacted the resulting racemic enolate with benzaldehyde (2) producing selectively a racemic mixture of only one of four possible diastereoisomeric aldols (3a)-(3d) (Majewski & Zheng, 1991), as shown in the scheme below. Compounds of this type are important intermediates in the synthesis of tropane alkaloids (Lounasmaa, 1988).…”

Section: Commentmentioning

confidence: 99%

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Structure of 2-(α-hydroxybenzyl)-8-methyl-8-azabicyclo[3.2.1]octan-3-one

Li¹,

Quail²,

Zheng³

et al. 1993

Acta Crystallogr C

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Section: Commentmentioning

confidence: 81%

Section: Commentmentioning

confidence: 99%

Structure of 2-(α-hydroxybenzyl)-8-methyl-8-azabicyclo[3.2.1]octan-3-one

Li¹,

Quail²,

Zheng³

et al. 1993

Acta Crystallogr C

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“…In a first approach, tropinone 16 was converted to Z‐protected tropanone 17 by treatment with benzyl chloroformate and potassium carbonate 32,33. Subsequent deprotonation with a chiral lithium amide base generated in situ from ( S , S )‐bis(1‐phenylethyl)amine hydrochloride,30c,30d and treatment with pyNTf 2 (method B) gave enol triflate 19 in 78 % yield (Scheme ). Unfortunately, the enantiomeric excess of compounds 19/21 could not be determined because attempted separation of the enantiomers on chiral stationary GC phases failed.…”

Section: Resultsmentioning

confidence: 99%

Tropanes as Scaffolds for Phosphorus–Olefin Ligands and Their Application in Asymmetric Catalysis

2013

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Tropane‐derived phosphorus–olefin hybrid ligands bearing various combinations of P‐units (chiral BINOL‐derived units/achiral PPh2‐units) with a tropene skeleton (chiral/achiral) have been synthesized and used in Cu‐catalysed conjugate 1,4‐additions of diethylzinc to cyclic enones and in Rh‐catalysed 1,4‐additions of phenylboronic acid (Hayashi–Miyaura reaction) with cyclic and acyclic enones. Whereas in Cu‐catalysed reactions only moderate yields and ee values (up to 49 % ee) were obtained, up to 97 % ee was observed in the Hayashi–Miyaura reaction with various substrates. The most promising results in both reactions were achieved with ligands 11 and 15, which contain a chiral alkene/achiral P‐unit or an achiral alkene/chiral P moiety, respectively, and where the metal is complexed on the exo side of the tropene skeleton. In contrast, ligands with an endo coordination mode showed only low (13) or no activity (12) in all of the 1,4‐additions. NMR and ESI‐MS experiments revealed the presence of two cationic [RhI(15)2]+ species in solution.

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“…The other possible isomers, i.e., the endo forms, have never been isolated or described. Their appearance in some experiments has been mentioned [22]. We have made an effort to devise a way to identify these elusive endo isomers.…”

Section: Introductionmentioning

confidence: 99%

Determination of the relative configuration of tropinone and granatanone aldols by using TBDMS ethers

Łaźny¹,

Nodzewska²,

Sidorowicz³

et al. 2012

Beilstein J. Org. Chem.

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SummaryThe relative configurations of tert-butyldimethylsilyl (TBDMS) ethers of all four diastereomers of the aldols of tropinone (8-methyl-8-azabicyclo[3.2.1]octan-3-one), as well as of granatanone (9-methyl-9-azabicyclo[3.3.1]nonan-3-one), were determined from NMR data, and from the observed interconversion of the diastereomers (exo,anti to endo,syn and exo,syn to endo,anti). The exo forms invert to endo isomers in the presence of silica gel. The relative configuration of a new isomer of tropinone aldol accessible synthetically through the direct solventless reaction of tropinone and benzaldehyde in the presence of water was determined as exo,syn by comparison of NMR data of the aldol isomers, in particular vicinal coupling constants and shifts corresponding to the side-chain CH group, with data of related TBDMS derivatives and confirmed by single-crystal X-ray diffraction.

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Enantioselective Deprotonation of Tropinone and Reactions of Tropinone Lithium Enolate

Cited by 28 publications

References 0 publications

Structure of 2-(α-hydroxybenzyl)-8-methyl-8-azabicyclo[3.2.1]octan-3-one

Structure of 2-(α-hydroxybenzyl)-8-methyl-8-azabicyclo[3.2.1]octan-3-one

Tropanes as Scaffolds for Phosphorus–Olefin Ligands and Their Application in Asymmetric Catalysis

Determination of the relative configuration of tropinone and granatanone aldols by using TBDMS ethers

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