A highly diastereo- and enantioselective cyclopropanation reaction was realized in the reaction of acyclic amides with monosubstituted allyl carbonates via Pd-catalysis using a ferrocene ligand with H as a substituent on an oxazoline ring, providing cyclopropane products having three chiral centers in yields of 67-83%, the dr ratio being 4-23:1, and ee being 83-97%. The presence of LiCl is important for the gain of high diastereo- and enantioselectivities of the reaction.
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http://dx.doi.org/10.1021/ja902410w | DOI Listing |
J Am Chem Soc
January 2025
Frontiers Science Center for Transformative Molecules, Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Direct synthesis of enantioenriched scaffolds with multiple adjacent stereocenters remains an important yet challenging task. Herein, we describe a highly diastereo- and enantioselective Cu-catalyzed alkylboration of cyclopropenes, with less reactive alkyl iodides as electrophiles, for the efficient synthesis of -substituted borylated cyclopropanes bearing three consecutive stereocenters. This protocol features mild conditions, a broad substrate scope, and good functional group tolerance, affording an array of chiral borylated cyclopropanes in good to high yields with excellent diastereo- and enantioselectivities.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
January 2025
Center of Basic Molecular Science (CBMS), Department of Chemistry, Tsinghua University, Beijing, 100084, China.
Enantioselective hydrogenation of tetrasubstituted alkenes to form 1,2-contiguous stereocenters is a particularly appealing but highly challenging transformation in asymmetric catalysis. Despite the notable progress achieved in enantioselective hydrogenation over the past decades, enantioselective hydrogenation of all-carbon tetrasubstituted alkenes containing multiple alkyl groups remains an unsolved challenge. Here, we report a rhodium-catalyzed highly diastereo- and enantioselective hydrogenation of diverse acyclic multisubstituted alkenes under mild conditions.
View Article and Find Full Text PDFChemistry
December 2024
Chemistry and Chemical Engineering Guangdong Laboratory, Shantou, China.
The convergent total synthesis of ixabepilone and its analogues in a 13-step longest linear sequence is reported. The crucial chiral centers at challenging C3-O, C8-C and C15-N positions on the scaffold of the ixabepilone were installed via highly efficient asymmetric hydrogenations (up to 95 % yield and up to 99 % e.e.
View Article and Find Full Text PDFChem Commun (Camb)
January 2025
Department of Chemistry, Indian Institute of Technology Jammu, Jagti, NH-44, Nagrota Bypass, Jammu 181221, J&K, India.
A highly regio-, enantio- and diastereo-selective strategy involving initial enantioselective conjugate addition to 4-nitro-5-styrylisoxazoles serves as a key step for the desymmetrization of 2,5-cyclohexadienones has been disclosed. We have designed a new class of 2,5-cyclohexadienones appended with 4-nitro-5-styrylisoxazoles to undergo organocatalytic asymmetric double or triple conjugate addition in a domino sequence depending on the substrate type leading to desymmetrization of the 2,5-cyclohexadienone core. The developed protocol allows the construction of a valuable hydrophenanthrene core or a unique bridged scaffold bearing multiple chiral centers with excellent enantio- (up to >99.
View Article and Find Full Text PDFChemistry
December 2024
Department of Chemistry, University of Kaiserslautern-Landau, Erwin-Schrödinger-Str. 54, 67663, Kaiserslautern, Germany.
A highly stereoselective Brønsted-acid catalyzed synthesis of densely substituted spiroisoindolinones from enamides and 3-hydroxy-isoindolinones is described. With simple Brønsted-acids, such as para-toluene sulfonic acid, spiroisoindolinones with three contiguous stereogenic centers are formed in high yields (up to 97 %) and diastereoselectivities (up to >98 : <2 : 0 : 0 dr) under mild reaction conditions. With the use of a chiral phosphoric acid catalyst, a diastereo- and enantioselective synthesis of the corresponding spiroisoindolinones was achieved.
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