Thiourea-catalyzed direct reductive amination of aldehydes

Synlett

Volumn , Issue 6, 2006, Pages 841-844

  Menche, Dirk ^a   Arikan, Fatih ^a  

^a HELMHOLTZ CENTRE FOR INFECTION RESEARCH   (Germany)

Author keywords

Aminations; Amines; Hydrogen bonds; Organocatalysis; Reductions

Indexed keywords

ALDEHYDE DERIVATIVE; AMINE; BENZALDEHYDE DERIVATIVE; ESTER DERIVATIVE; THIOUREA;

AMINATION; ARTICLE; CATALYSIS; CATALYST; CHEMICAL STRUCTURE; HYDROGEN BOND; HYDROGENATION; REDUCTION; SYNTHESIS;

EID: 33645755227     PISSN: 09365214     EISSN: None     Source Type: Journal    
DOI: 10.1055/s-2006-939052     Document Type: Article

References (30)

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24. 2 are as suitable as toluene, while more polar solvents such as dioxane or THF are less efficient. Protic solvents (e.g. MeOH) are of limited applicability.
25. (b) Upon extended reaction times, the transformation may also be carried out at r.t.
26. General Procedure. A solution of the aldehyde (1a-f, 2.20 mmol) and the amine (2a-g, 2.00 mmol) in toluene (5 mL) is treated with the Hantzsch ester (3,608 mg, 2.40 mmol), thiourea (4,15.2 mg, 0.200 mmol) and MS 5 Å (2.0 g). The mixture is stirred 24 h at 70 °C under nitrogen. After filtration over Celite®, the solvent is evaporated and the residue purified by flash chromatography on silica gel using mixtures of PE and EtOAc as eluants to give the product amines (5a-1) in pure form.
27. (a) The catalyst loading may be reduced to 1 mol% upon extended reaction times (>48 h).
28. (b) Under the same reaction conditions but in the absence of thiourea, the product amine is only obtained in low yields proving the vital influence of the organocatalyst.
29. This assumption is supported by previous calculations on related thiourea complexes with aldimines and amines: Vachal, P.; Jacobsen, E. N. J. Am. Chem. Soc. 2002, 124, 10012.
30. +: 242.1181. Found: 242.1178.