Enantioselective aldehyde α-nitroalkylation via oxidative organocatalysis

Journal of the American Chemical Society

Volumn 131, Issue 32, 2009, Pages 11332-11334

  Wilson, Jonathan E ^a   Casarez, Anthony D ^a   MacMillan, David W C ^a  

^a PRINCETON UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

AMINE CATALYSTS; ANTI ISOMERS; CHEMICAL EQUATIONS; ENAMINE INTERMEDIATES; ENANTIOSELECTIVE; ORGANOCATALYSIS; ORGANOCATALYTIC; OXIDATIVE COUPLINGS; SILYL GROUP;

AMINES; AMINO ACIDS; AROMATIC HYDROCARBONS; CATALYSIS; ORGANIC ACIDS; REACTION KINETICS; SILANES;

ALDEHYDES;

ALDEHYDE DERIVATIVE; AMINE; ENAMINE;

ALKYLATION; ARTICLE; CATALYST; CHEMICAL BOND; CHEMICAL STRUCTURE; COUPLING FACTOR; ENANTIOSELECTIVITY; ISOMER; POLYMERIZATION; SYNTHESIS;

ALDEHYDES; ALKYLATION; AMINES; AMINO ACIDS; CATALYSIS; MODELS, MOLECULAR; MOLECULAR STRUCTURE; OXIDATION-REDUCTION; STEREOISOMERISM;

EID: 68849107137     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja904504j     Document Type: Article

References (26)

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16. Notably, silyl nitronates can be employed in enantioselective Henry reactions with aldehydes under nonoxidative conditions. See: (a) Risgaard, T.; Gothelf, K. V.; Jørgensen, K. A. Org. Biomol. Chem. 2003, 1, 153.
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19. (a) We measured the oxidation potentials of the standard silyl nitronates used in our studies and found them to be slightly lower than the values reported for enamines (see ref 9b): for tert-butyldimethylsilyl propylideneazinate, E° = 0.45 V vs SCE; for triisopropylsilyl propylideneazinate, E° = 0.47 V vs SCE. However, because these potentials are thermodynamic in nature and there is a strong overpotential when CAN is employed, it is impossible to predict a priori whether the enamine or the silyl nitronate will be kinetically more prone to oxidation by CAN using these values.
20. (b) Schoeller, W. W.; Niemann, J.; Rademacher, P. J. Chem. Soc., Perkin Trans. 2 1988, 369.
21. Performed at the B3LYP/6-311+G(2d,p)//B3LYP/6-31G(d) level (see ref 6a).
22. Relative stabilities of silyl ethers toward base hydrolysis: TMS (1) < TES (10-100) < TBDMS ≈ TBDPS (20 000) < TIPS (100 000). These values were taken from: Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis, 3rd ed.; John Wiley & Sons: New York, 1999.
23. 3 as the base generally increases the amount of syn β-nitroaldehyde produced.
24. 6 after 3 h, while TIPS nitronate remained unchanged under identical conditions.
25. Allyl trimethylsilane readily functions as a SOMOphile to react with radical cations (see ref 6a), but it does not itself undergo oxidation to form a radical cation under these conditions.
26. See the Supporting Information for further details.