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Synlett
Volumn , Issue 11, 2009, Pages 1757-1760
Novel chiral C2-symmetric bisimidazole-N-oxides as promising organocatalysts for enantioselective allylation of aromatic aldehydes
Author keywords

Allylation; Asymmetric catalysis; Chiral imidazole N oxides; Nucleophilic addition; Organocatalysis
Indexed keywords

ALDEHYDE; ALLYL ALCOHOL; CYCLOHEXYLAMINE DERIVATIVE; IMIDAZOLE DERIVATIVE; SILANE DERIVATIVE;
EID: 67649976824     PISSN: 09365214     EISSN: 14372096     Source Type: Journal    
DOI: 10.1055/s-0029-1217365     Document Type: Article
Times cited : (30)
References (39)
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    • For reviews on asymmetric organocatalysis, see: a, Dalko, P. I, Ed, Wiley-VCH: Weinheim
    • For reviews on asymmetric organocatalysis, see: (a) Enantioselective Organocatalysis; Dalko, P. I., Ed.; Wiley-VCH: Weinheim, 2007.
    • (2007) Enantioselective Organocatalysis
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    • List, B., Ed. Chem. Rev. 2007, 107, 5413-5883.
    • (b) List, B., Ed. Chem. Rev. 2007, 107, 5413-5883.
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    • For recent examples of asymmetric reactions catalyzed by chiral pyridine-derived N-oxides, see: (a) Malkov, A. V.; Westwater, M.-M.; Gutnov, A.; Ramírez-López, P.; Friscourt, F.; Kadlčí ková, A.; Hodačová, J.; Rankovic, Z.; Kotora, M.; Kočovský, P. Tetrahedron 2008, 64, 11335.
    • For recent examples of asymmetric reactions catalyzed by chiral pyridine-derived N-oxides, see: (a) Malkov, A. V.; Westwater, M.-M.; Gutnov, A.; Ramírez-López, P.; Friscourt, F.; Kadlčí ková, A.; Hodačová, J.; Rankovic, Z.; Kotora, M.; Kočovský, P. Tetrahedron 2008, 64, 11335.
  • 11
    • 42149130246 scopus 로고    scopus 로고
    • Malkov, A. V.; Ramírez-López, P.; Biedermannová, L. (née Bendová); Rulíek, L.; Dufková, L.; Kotora, M.; Zhu, F.; Kočovský, P. J. Am. Chem. Soc. 2008, 130, 5341.
    • (b) Malkov, A. V.; Ramírez-López, P.; Biedermannová, L. (née Bendová); Rulíek, L.; Dufková, L.; Kotora, M.; Zhu, F.; Kočovský, P. J. Am. Chem. Soc. 2008, 130, 5341.
  • 21
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    • For recent examples of asymmetric reactions catalyzed by chiral N-oxides derived from tertiary amines, see: (a) Simonini, V.; Benaglia, M.; Pignataro, L.; Guizzetti, S.; Celentano, G. Synlett 2008, 1061.
    • For recent examples of asymmetric reactions catalyzed by chiral N-oxides derived from tertiary amines, see: (a) Simonini, V.; Benaglia, M.; Pignataro, L.; Guizzetti, S.; Celentano, G. Synlett 2008, 1061.
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    • For reviews on application of chiral N-oxides in asymmetric catalysis, see: (a) Benaglia, M.; Guizzetti, S.; Pignataro, L. Coord. Chem. Rev. 2008, 252, 492.
    • For reviews on application of chiral N-oxides in asymmetric catalysis, see: (a) Benaglia, M.; Guizzetti, S.; Pignataro, L. Coord. Chem. Rev. 2008, 252, 492.
  • 34
    • 68049137588 scopus 로고    scopus 로고
    • Typical Procedure for the Preparation of Bisimidazole N-Oxides, Synthesis of (1R,2R)-1d To a stirred soln of (1R,2R)-trans-1,2-diamonocyclohexane (114.0 mg, 1.0 mmol) in MeOH (3 mL, a portion of paraformaldehyde (63.0 mg, 2.1 mmol) was added and the soln was stirred overnight at ambient temperature. After evaporation of the solvent in vacuum, the resulting, viscous oil was dissolved in glacial acid (7 mL) containing 473 mg (2.1 mmol) α-benzil monoxime 3d and the soln obtained thereby was stirred overnight at ambient temperature. Next day, a gentle stream of gaseous HCl was bubbled through the soln for ca. 1.5 h, and the separated colorless bisimidazole N-oxide hydrochloride was filtered off and dried in vacuum exsiccator. The crude hydrochloride was suspended in MeOH (ca 25 mL) and 1 g of the solid NaHCO3 was added; stirring was continued for ca.1.5 h until evolution of CO2
    • 20 +6.0 (c 1.02; MeOH). For X-ray structure determination of (1R,2R)- and (1S,2S)-1d, see: Mloston G., Mucha P., Tarka R., Urbaniak K., Linden A., Heimgartner H.; Polish J. Chem.; 2009, 83, 1105.
  • 36
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    • For reviews on asymmetric allylation of carbonyl compounds, see: a
    • For reviews on asymmetric allylation of carbonyl compounds, see: (a) Denmark, S. E.; Fu, J. Chem. Rev. 2003, 103, 2763.
    • (2003) Chem. Rev , vol.103 , pp. 2763
    • Denmark, S.E.1    Fu, J.2
  • 39
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    • General Allylation Procedure To a stirred soln of the catalyst 1d (27.7 mg, 0.05 mmol) in dry CH2Cl2 (1 mL) the corresponding aldehyde 4 (0.5 mmol) and dry diisopropylethylamine (260 μL, 1.5 mmol) were added. After 5 min. magnetic stirring at 0 °C, allyltrichlorosilane (90-95 μL, 0.6 mmol) was added to the reaction mixture. Stirring was continued at 0 °C for another 20 h, and after this time the mixture was firstly diluted with Et2O, quenched with aq NaHCO 3 (1 mL) and next shaken with H2O. Organic layer was separated and the aqueous soln was extracted again with Et2O (2 × 10 mL, combined ethereal soln were dried over MgSO4, filtered, and concentrated. The residue was purified by silica gel column chromatography. Yields refer to the isolated amount of alcohol 5. The ee was determined using HPLC technique with chiral column Chiralcel OD-H or Chiralpak AS-H, mix
    • 4, filtered, and concentrated. The residue was purified by silica gel column chromatography. Yields refer to the isolated amount of alcohol 5. The ee was determined using HPLC technique with chiral column (Chiralcel OD-H or Chiralpak AS-H); mixture of 2-PrOH-hexane was applied as an eluent.

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