1,720,975 research outputs found
PROCESS FOR THE STEREOSELECTIVE REDUCTION OF KETOIMINES CATALYSED BY TRICHLOROSILANE
No full textThe invention relates to a process for the preparation of enantiomerically enriched amines from ketoimines with trichlorosilane in the presence of picolinic acid derivatives of general formula (I) wherein R1-R7 are as defined in the description as catalysts
Enantioselective catalytic reduction of ketimines with trichlorosilane promoted by readily available chiral Lewis Bases
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Trichlorosilane-mediated stereoselective reduction of carbon-nitrogen double bonds
No full textThe reduction of C=N bonds represents a powerful and widely used transformation allowing new nitrogen-containing stereocenters to be generated. Chiral amino groups are ubiquitous in a variety of bioactive molecules such as alkaloids, natural products, drugs, and medical agents, so the development of a catalytic stereoselective process for the preparation of enantiomerically enriched amines through ketoimine reduction is attracting increasing interest, especially in view of future industrial applications. Great efforts to develop efficient organocatalytic methods to perform enantioselective imine reductions and reductive amination processes have recently been made. In the last few years, trichlorosilane-mediated reductions have received constantly increasing attention because the potential to generate chiral catalysts for imine reduction simply by coordination of HSiCl3 with a chiral Lewis base has allowed the development of several efficient organocatalytic systems. Here we offer a complete overview of different chiral promoters of stereoselective reductions with trichlorosilane, classified as N-formyl derivatives, which may be considered historically the first class of compounds developed as chiral activators of trichlorosilane, picolinamide derivatives, and miscellaneous compounds presented in that order. C=N bond reduction is a powerful, widely used transformation allowing new nitrogen-bearing stereocenters to be created. Generation of chiral catalysts for imine reduction simply by coordination of HSiCl3 with chiral Lewis bases has allowed the development of several efficient organocatalytic systems. An overview of chiral promoters for stereoselective C=N reductions with HSiCl3 is provided
Stereoselective reactions involving hypervalent silicate complexes
No full textIn the last few years the possibility of effectively employing relatively simple organic molecules as enantioselective catalysts able to promote reactions with high levels of chemical efficiency and stereocontrol has been demonstrated. In this context chiral Lewis bases play an important role as promoters of a large variety of stereoselective reactions. In the field of silicon-based chemistry several, new metal-free compounds have recently been developed to efficiently catalyze different reactions where “hypervalent” silicates are involved as intermediates. The review will present the more recent achievements in silicate-mediated stereoselective reactions catalyzed by chiral Lewis bases
Highly stereoselective metal-free catalytic reduction of imines: an easy entry to enantiomerically pure amines and natural and unnatural -amino esters.
No full textA highly efficient catalytic stereoselective ketlmlne reduction is described. The combination of an Inexpensive chiral organocatalyst, easily prepared In a single step, and of a very cheap removable chiral auxiliary allowed us to obtain enantlomerlcally pure amino compounds. The methodology allowed synthesis of chiral secondary and primary amines and natural and unnatural amino esters In high yields often with total control of the absolute stereochemistry
Enantioselective Direct Aldol Reaction “on water” Promoted by Chiral Organic Catalysts
No full text1,1¢-Binaphthyl-2,2¢-diamine-based (S)-prolinamides in the presence of stearic acid were able to promote the direct aldol condensation of
cyclohexanone and other ketones with different aldehydes in the presence of a massive amount of water in very good yields, high
diastereoselectivity, and up to 99% ee. The behavior of both C2- and C1-symmetric catalysts in combination with different additives was
investigated, and a preliminary experiment of recovering and recycling of the catalytic system was also attempted
Poly(methylhydrosiloxane)-supported chiral organic catalysts
No full textPolymer-supported organic catalysts will be discusse
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