The chiral aziridine-containing vicinal iminophenol tridentate ligands (named salazins) are a class of readily prepared chiral ligands from enantiopure aziridines and salicylaldehydes. Their scandium and yttrium triflate complexes show excellent reactivity and enantioselectivities in the catalytic asymmetric aldol condensation of electron-deficient aromatic aldehydes and ketones, including acetone and cycloalkanones. The stereoselectivity is rationalized to the strong π-stacking interaction between aromatic aldehydes and the vicinal iminophenol group in the chiral ligands.
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http://dx.doi.org/10.3390/molecules29091963 | DOI Listing |
Org Lett
January 2025
Department of Chemistry, Indian Institute of Science Education and Research (IISER) Bhopal, Bhopal By-pass Road, Bhauri, Bhopal 462066, India.
The successful implementation of a cascade reaction involving a cyclobutyl unit has posed a significant challenge in achieving ring-retentive functionalization because of the ring's sacrificial tendency. Herein, we have accomplished a cinchona-derived squaramide-catalyzed cascade reaction sequence, encompassing the desymmetrization of cyclobutanone, followed by an aldol reaction and, subsequently, a 1,4-addition step. This overall process offers a viable strategy to access architecturally fascinating oxa-spirocycles fused with cyclobutanone motifs in good yields with high optical purity.
View Article and Find Full Text PDFChemistry
December 2024
Southern University of Science and Technology, Chemistry, 1088 Xueyuan Avenue, 518055, Shenzhen, 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 PDFOrg Lett
December 2024
School of Pharmacy, Jiangsu University, Zhenjiang 212013, China.
Utilizing enzymes as biocatalysts, an alternative strategy has been developed for the highly enantioselective synthesis of chiral 2,3-dihydrobenzofuran (2,3-DHB) esters via the dynamic kinetic resolution of 2,3-dihydro-3-benzofuranols, which are generated from an intramolecular Aldol reaction. This protocol provides easy access to a series of 2,3-DHB ester derivatives, prodrugs, and allows for functional group transformations. Biological evaluation also indicates that some of the products exhibit potent anti-inflammatory activity.
View Article and Find Full Text PDFOrg Lett
December 2024
Molecular Synthesis Center & Key Laboratory of Marine Drugs, Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, China.
A regiodivergent strategy for the asymmetric diversity-oriented synthesis of spirooxindoles via organocatalytic cascade reactions is developed. Two regioselective pathways can be precisely controlled with different aminocatalysts in the reaction of 2-hydroxycinnamaldehydes and β,β-disubstituted 3-alkylidene oxindoles. The cascade vinylogous Michael/oxa-Michael/aldol reactions gave spiro-bridged oxindoles bearing two adjacent quaternary stereocenters, while the cascade oxa-Michael/Michael reactions gave spirooxindoles.
View Article and Find Full Text PDFMacromol Rapid Commun
November 2024
PCFM, LIFM Lab and GD HPPC Lab, School of Chemistry, Sun Yat-sen University, Guangzhou, 510275, P. R. China.
Nanostructures with curved surfaces and chiral-directing residues are highly desirable in the synthesis of asymmetric chemicals, but they remain challenging to synthesize without using unique templates due to the disfavored torsion energy of twisted architectures toward chiral centers. Here, a strategy for the facile fabrication of highly cured capsule-shaped catalysts with chiral interiors by the amplification of molecular chirality via the irreversible cross-linking of 2D asymmetric laminates is presented. The key to the success of these irregular 2D layers is the use of hierarchical assembly of chiral macrocycles, which can exactly regulate the cured nanostructures as well as asymmetric catalysis.
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