Divergent Stereoinduction Mechanisms in Urea-Catalyzed Additions to Imines

Synlett

Volumn , Issue 12, 2003, Pages 1919-1922

  Wenzel, Anna G ^a   Lalonde, Mathieu P ^a   Jacobsen, Eric N ^a  

^a HARVARD UNIVERSITY   (United States)

Author keywords

Asymmetric catalysis; Imines; Nucleophilic additions; Organocatalysis; Substituent effects

Indexed keywords

AMINO ACID DERIVATIVE; IMINE; KETENE DERIVATIVE; N TERT BUTYLOXYCARBONYLBENZALDIMINE; THIOUREA DERIVATIVE; UNCLASSIFIED DRUG; UREA;

ADDITION REACTION; ARTICLE; CATALYSIS; CATALYST; CHEMICAL COMPOSITION; CHEMICAL STRUCTURE; ENANTIOSELECTIVITY; MANNICH REACTION; MOLECULAR WEIGHT; REACTION ANALYSIS; STEREOCHEMISTRY; STRECKER SYNTHESIS; STRUCTURE ANALYSIS;

EID: 0142091315     PISSN: 09365214     EISSN: None     Source Type: Journal    
DOI: 10.1055/s-2003-41503     Document Type: Article

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32. 5e and Wenzel, A. G., unpublished results).
33. The standard screening conditions are depicted in Scheme 1. Benzaldimines were chosen as substrates for each reaction to maximize structural and electronic similarity. While aliphatic N-alkyl imines have been successfully employed in the Strecker reaction, aliphatic N-Boc aldimines have not been investigated in the Mannich reaction because no useful method has been identified for their synthesis.
34. 5c)
35. In general, conversion was found to correlate with enantioselectivity, with the more selective catalysts also proving to be the most reactive.
36. 5a
37. 6).
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41. Analogs of 24 derived from less sterically demanding amino acids (e.g. valine, alanine) also performed poorly as catalysts for the Mannich reaction. Catalyst 24 proved almost completely unreactive in the Strecker reaction.
42. The model Strecker reaction was catalyzed by 26 in 40% ee with the opposite sense of stereoinduction relative to 1.
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