Reductive coupling of imines

In order to achieve a satisfactory preparation of C2-symmetric (R,R)- or (S,S)-diamines, it is necessary to avoid or minimize the formation of the 

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Scheme 2 Mechanism of the electrochemical or metal-promoted reductive coupling of imines in an acidic medium...

Reductive coupling of imines 43 (R1 = Me, Ph or 2-pyridyl R2 = Me, Pr, t-Bu or PI1CH2) in THF under the influence of a low-valent titanium species, produced by the action of magnesium amalgam on titanium(IV) chloride, gave the DL-diamines... 

The following combinations have also been reported of titanium-mediated reductive coupling of imines TiCU-Mg in DME (or THF), TiCU-Li in DME (or THF), TiCU-EtjN in Catalytic use of... 

Sm[N(SiMe3)2l2, a reductant stronger than Sml2, is also effective for reductive coupling of imines. 

Reductive coupling of imines.2 Aromatic ketimines are reduced to the corresponding secondary amines by Sml2, but aromatic aldimines couple to 1,2-diamines (equation II). 

Zirconaaziridines prepared through the addition of imine to zirconocene are generally not of high purity and cannot be isolated in high yield reductive coupling of imines often competes. However, this method is preferred for preparing zirconaaziridines in situ for reaction with electrophiles that can be... 

Reductive coupling of imines. A I I) on heating with indium rod in aquei in 40-100% yield. Simple reduction side... 

SET reduction of ketones Reductive amination Reductive coupling of imines Reformatsky reaction Ring-opening of strained heterocycles... 

Schemes Sm-promoted reductive coupling of chiral C-aryl imines...

Moreover, a dramatic increase of the reaction rate was observed when the coupUng of aromatic imines mediated by samariiun diiodide was carried out in the presence of both water and a tertiary amine or tetramethylethylene-diamine (TMEDA) [29], causing the almost instantaneous formation of the 1,2-diamine, although with undetermined diastereoselectivity. Similarly, the samarium diiodide promoted reductive coupling of iminiiun ions formed in situ by reacting ahphatic aldehydes with secondary amines and benzotriazole occurred at temperatures as low as - 70 °C [30]. Even in this case a mixture of diastereomers with undetermined ratio was obtained nevertheless, the item of diastereoselectivity induced by a chiral amine (auxiliary) is worthy of investigation. 

An approach to the preparation of asymmetrically 1,2-disubstituted 1,2-diamines has been reported the zinc-copper-promoted reductive coupling of two different N-(4-substituted)phenyl aromatic imines, one bearing a 4-methoxy and the other a 4-chloro substituent, in the presence of either boron trifluoride or methyltrichlorosilane, gave a mixture of the three possible 1,2-diamines, where the mixed one predominated [31 ]. Low degrees of asymmetric induction were observed using 1-phenylethylamine, phenylglycinol and its 0-methyl ether, and several a-amino acid esters as the chiral auxiharies meanwhile the homocoupling process was not avoided (M.Shimizu, personal communication). 

The asymmetric synthesis of unsymmetrical vicinal diamines by samarium diiodide induced reductive coupling of nitrones derived from aUphatic aldehydes with optically pure N-tert-butanesulfinyl aromatic imines has been recently reported [41]. For example, the reaction between nitrone 55 and... 

The Cp2VCl2/R3SiCl/Zn catalytic system can be used for the reductive coupling of the imines 29 (Scheme 18) [55]. These components of the ternary catalyst are essential and, interestingly, meso-diastereoselectivity is observed in contrast to the coupling with cat. Cp2TiCl2/Sm system. The selectivity de-... 

Catalytic Reductive Coupling of Alkenes and Alkynes to Carbonyl Compounds and Imines Mediated by Hydrogen... 

Scheme 13 Enantioselective carbonyl (Z)-dienylation via reductive coupling of acetylene to aldehydes and imines mediated by hydrogen...

Ihmels H, Otto D (2005) Intercalation of Organic Dye Molecules into Double-Stranded DNA - General Principles and Recent Developments. 258 161-204 Iida H, Krische MJ (2007) Catalytic Reductive Coupling of Alkenes and Alkynes to Carbonyl Compounds and Imines Mediated by Hydrogen. 279 77-104 Imai H (2007) Self-Organized Formation of Hierarchical Structures. 270 43-72 Indelli MT, see Chiorboli C (2005) 257 63-102 Inoue Y, see Borovkov VV (2006) 265 89-146 Ishii A, Nakayama J (2005) Carbodithioic Acid Esters. 251 181-225 Ishii A, Nakayama J (2005) Carboselenothioic and Carbodiselenoic Acid Derivatives and Related Compounds. 251 227-246... 

Reductive Coupling of Conjugated Enynes and Diynes with Activated Aldehydes and Imines... 

The [lrCl(cod)]2-catalyzed reductive coupling of acrylates and imines provides trans-P-lactams with high diastereoselectivity (Equation 10.39) [67]. With regards to the reaction mechanism, in situ generated Ir-hydride reacts with acrylate 148 to produce an Ir enolate, which then reacts with the 147 to afford the P-amido ester 149. 

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