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Boc Imines (boc + imine)
Selected AbstractsPdII -Catalyzed Asymmetric Addition Reactions of 1,3-Dicarbonyl Compounds: Mannich-Type Reactions with N -Boc Imines and Three-Component AminomethylationCHEMISTRY - AN ASIAN JOURNAL, Issue 8-9 2008Yoshitaka Hamashima Dr. Abstract This paper describes catalytic asymmetric Mannich-type reactions of ,-ketoesters and malonates using chiral palladium complexes. Although readily enolizable, carbonyl compounds are attractive substrates, the use of such compounds as nucleophiles in Mannich-type reactions has not been extensively investigated. In the presence of chiral Pd aqua complexes (2.5,mol,%), ,-ketoesters reacted with various N -Boc imines (Boc=tert -butoxycarbonyl) to afford the desired ,-aminocarbonyl compounds in good yield with high to excellent stereoselectivity (up to 96:4 d.r., 95,99,%,ee in most cases). In these reactions, construction of highly crowded vicinal quaternary and tertiary carbon centers was achieved in one step. A chiral Pd enolate is considered to be the key intermediate. To elucidate the stereoselectivity observed in the reaction, possible transition-state models are discussed, taking into account steric and stereoelectronic effects. Furthermore, this catalytic system was applied to the Mannich-type reaction of malonates with N -Boc imine as well as one-pot classical aminomethylation of ,-ketoesters using benzylamine salt and formalin. The reactions proceeded smoothly, and the corresponding Mannich products were obtained in high yield with moderate to good enantioselectivity. [source] Asymmetric Aza-Morita,Baylis,Hillman Reactions of Alkyl Vinyl Ketones with N -Protected Imines or In Situ Generated N -Protected IminesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2010Xiao-Yang Guan Abstract DABCO-catalyzed aza-MBH reactions of N -Boc imines with MVK and EVK have been thoroughly investigated in the paper. The asymmetric version of this aza-MBH reaction was also systematically investigated by using a chiral amine or a chiral phosphane catalyst. It was found that most of the N -protected imines are suitable substrates under the mild reaction conditions and are able to give the corresponding adducts in moderate yields with high ee values. The TQO- or LB1-catalyzed aza-MBH reactions of N -protected ,-amidoalkyl phenyl sulfones or ,-amidoalkyl p -tolyl sulfones with MVK could be well conducted, which provides a facile and direct route to obtain highly enantioselective aza-MBH adducts. The Boc protecting group of the aza-MBH product could be easily removed under acidic conditions to give the corresponding ,-methylene-,-amino ketone or ,-methylene-,-amino alcohol derivatives in good yields. [source] A Novel Bis-Thiourea Organocatalyst for the Asymmetric Aza-Henry ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2008Constantinos Rampalakos Abstract A novel bis-thiourea/2,2,-diaminobinaphthalene (BINAM)-based catalyst for the asymmetric aza-Henry reaction has been developed. This catalyst promotes the reaction of N -Boc imines with nitroalkanes to afford ,-nitroamines with good yields and high enantioselectivities. This catalyst has the advantage that it can be prepared in a single step from commercially available materials. A model is proposed for the catalyst action where both components of the reaction are activated simultaneously by hydrogen bonding. Regardless of the mechanism, the success of the present catalyst demonstrates the potential of bis-thioureas as an interesting class of relatively unexplored catalysts. [source] PdII -Catalyzed Asymmetric Addition Reactions of 1,3-Dicarbonyl Compounds: Mannich-Type Reactions with N -Boc Imines and Three-Component AminomethylationCHEMISTRY - AN ASIAN JOURNAL, Issue 8-9 2008Yoshitaka Hamashima Dr. Abstract This paper describes catalytic asymmetric Mannich-type reactions of ,-ketoesters and malonates using chiral palladium complexes. Although readily enolizable, carbonyl compounds are attractive substrates, the use of such compounds as nucleophiles in Mannich-type reactions has not been extensively investigated. In the presence of chiral Pd aqua complexes (2.5,mol,%), ,-ketoesters reacted with various N -Boc imines (Boc=tert -butoxycarbonyl) to afford the desired ,-aminocarbonyl compounds in good yield with high to excellent stereoselectivity (up to 96:4 d.r., 95,99,%,ee in most cases). In these reactions, construction of highly crowded vicinal quaternary and tertiary carbon centers was achieved in one step. A chiral Pd enolate is considered to be the key intermediate. To elucidate the stereoselectivity observed in the reaction, possible transition-state models are discussed, taking into account steric and stereoelectronic effects. Furthermore, this catalytic system was applied to the Mannich-type reaction of malonates with N -Boc imine as well as one-pot classical aminomethylation of ,-ketoesters using benzylamine salt and formalin. The reactions proceeded smoothly, and the corresponding Mannich products were obtained in high yield with moderate to good enantioselectivity. [source] | ||||||||||