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ABSTRACT: Iridium-catalyzed, asymmetric allylation of ammonia as a nucleophile occurs with stereoselectivity to form a symmetric diallylamine, and related allylation of the inexpensive ammonia equivalent potassium trifluoroacetamide or the highly reactive ammonia equivalent lithium di-tert-butyliminodicarboxylate forms a range of conveniently protected, primary, alpha-branched allylic amines in high yields, high branched-to-linear regioselectivities, and high enantiomeric excess. The reactions of ammonia equivalents were conducted with a catalyst generated from a phosphoramidite containing a single stereochemical element.
Organic Letters 10/2007; 9(20):3949-52. · 5.86 Impact Factor
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ABSTRACT: A catalytic protocol for the conversion of readily accessible racemic, branched aromatic allylic esters to branched allylic amines, ethers, and alkyls has been developed. Palladium-catalyzed isomerization of branched allylic esters to terminal allylic esters, followed by sequential iridium-catalyzed allylic substitution, gave the branched allylic products in good yield with high regioisomeric and enantiomeric selectivity. Both electron-rich and electron-poor branched allylic esters gave products in >90% ee. High enantiomeric excesses were also observed for the products from the reactions of 2-thienyl acetates and dienyl carbonates.
Journal of the American Chemical Society 09/2006; 128(36):11770-1. · 9.91 Impact Factor
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ABSTRACT: A study of the relationship between the stereochemical elements of a phosphoramidite ligand and the stereoselectivity of iridium-catalyzed amination of allylic carbonates is reported. During catalyst activation, a complex of a phosphoramidite ligand possessing one axial chiral binaphtholate group and two resolved phenethyl substituents converts to a more reactive cyclometalated complex containing one distal chiral substituent at nitrogen, one substituent that becomes part of the metalacycle, and one unperturbed binaphtholate group. Systematic changes were made to the different stereochemical elements. Replacement of the distal chiral phenethyl substituent with a large achiral cycloalkyl group led to a catalyst that reacts with rates and enantioselectivities that are similar to those of the original catalyst with the phenethyl group. Studies of the reactions of diastereomeric ligands containing (R) or (S) binaphtholate groups on phosphorus, along with one (R)-phenethyl and one achiral cyclododecyl group on nitrogen, show that the complexes of the two diastereomeric ligands undergo cyclometalation at much different rates. To access both diastereomeric catalysts and to determine if the reaction can occur selectively with an even simpler ligand containing a phenethyl substituent at nitrogen as the only resolved stereochemical element, the catalyst derived from a phosphoramidite containing a biphenolate group was studied. Catalysts generated from this ligand were shown to react in all cases examined with nearly the same rates, regioselectivities, and enantioselectivities as catalysts derived from the original more elaborate ligand. The absolute stereochemistry of the product implies that the major enantiomer is formed from the (R(a),R(c))-atropisomer of the catalyst containing the biphenolate group.
Journal of the American Chemical Society 12/2005; 127(44):15506-14. · 9.91 Impact Factor
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ABSTRACT: [reaction: see text] The yields, enantioselectivities, and regioselectivities of the reactions of amines and phenoxides with allylic carbonates in the presence of a metallacyclic iridium catalyst were compared. These data show that both preactivation of the catalyst and the size of the ligand affect the yield, enantioselectivity, and regioselectivity. With the activated catalyst containing a bis-naphthethylamino group, the allylic amination and etherification of a broad range of allylic carbonates occurred in high yields and with high regioselectivities and enantioselectivities.
Organic Letters 04/2005; 7(6):1093-6. · 5.86 Impact Factor
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ABSTRACT: An intermolecular, palladium-catalyzed addition of the alpha-C-H bond of monocarbonyl and 1,3-dicarbonyl compounds to dienes has been developed, and an exploration of the scope of these reactions with a broad range of carbonyl compounds and nitriles was conducted. The combination of CpPd(allyl) and the commercially available 1,3-bis(dicyclohexylphosphino)propane (DCyPP) catalyzed the 1:1 addition of the C-H bonds of these substrates to dienes in high yields. These reactions included unusual additions of the C-H bonds of ketones, lactones, esters, and nitriles to dienes, as well as the more common additions of cyanoesters, malononitrile, and alpha-sulfonyl esters. Reactions of these substrates with both cyclic and acyclic dienes are reported. Reactions catalyzed by complexes of nonracemic chiral ligands were also conducted, and the first enantioselective version of this reaction was achieved with a Josiphos ligand with enantioselectivities up to 81%.
The Journal of Organic Chemistry 11/2004; 69(22):7552-7. · 4.45 Impact Factor
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Angewandte Chemie International Edition 10/2004; 43(36):4797-800. · 13.45 Impact Factor
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ABSTRACT: Individual diastereomeric phosphoramidites and mixtures of diastereomeric phosphoramidites were evaluated in the iridium-catalyzed amination of allylic carbonates. The original process was conducted with a phosphoramidite ligand containing a resolved 2,2-dihydroxy-1,1-binaphthyl (BINOL) group and a diastereomerically and enantiomerically pure bis(phenethyl)amino group. Evaluation of the structure of the active catalyst and relative rates for reactions in the presence of catalysts containing diastereomeric ligands led to the identification of a phosphoramidite that provided the amination product with enantiomeric excess similar to the original, more structurally and stereochemically complex ligand and that contains a racemic BINOLate and an N-benzylphenethylamino group on phosphorus.
Proceedings of the National Academy of Sciences 05/2004; 101(16):5830-3. · 9.68 Impact Factor
