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Alkoxy-Directed Dienamine Catalysis in [4 + 2]-Cycloaddition: Enantioselective Synthesis of Benzo-[3]-ladderanol.
J Am Chem Soc
January 2025
Department of Organic Chemistry, Indian Institute of Science, Bangalore 560012, India.
Despite tremendous progress of dienamine catalysis along with its application in enantioselective synthesis over nearly two decades, certain limitations, especially with respect to the regioselectivity in the dienamine generation step, continue to persist. To overcome these shortcomings of classical dienamine catalysis, we now introduce the concept of alkoxy-directed dienamine catalysis and apply it to the enantioselective arene construction by desymmetrizing -enediones through [4 + 2]-cycloaddition. Catalyzed by a diphenylprolinol silyl ether, this reaction utilizes γ-alkoxy α,β-unsaturated aldehydes as the substrate and proceeds in a highly regioselective fashion through the intermediacy of δ-alkoxy dienamine.
View Article and Find Full Text PDFSwitch of Five Contiguous Chiral Centers in the Synthesis of Both Enantiomers of Hajos-Parrish Ketone Analogs via Diphenylprolinol Silyl Ether-Mediated Domino Reaction.
Chemistry
November 2024
Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aramaki Aza-Aoba, Aoba-ku, Sendai, Miyagi, 980-8578, Japan.
Both enantiomers of functionalized Hajos-Parrish ketone (HPK) analogs were prepared with excellent diastereoselectivities and enantioselectivities using the same chiral catalyst under two slightly different conditions. In condition A, dioxane was used as the solvent with 3 equivalents of water. In condition B, acetonitrile was used as the solvent with 30 equivalents of water, followed by epimerization with a base in a one-pot.
View Article and Find Full Text PDFAsymmetric Synthesis of α-Arylcyclohexenones Catalyzed by Diphenylprolinol Silyl Ether.
J Org Chem
August 2024
Department of Chemistry, Indian Institute of Technology Gandhinagar, Palaj, Gandhinagar, Gujarat 382055, India.
A general methodology for the asymmetric synthesis of α-arylcyclohexeneones from arylacetones and α,β-unsaturated aldehydes catalyzed by diphenylprolinol silyl ether followed by -TSA-mediated cyclization is developed. A variety of arylacetones and α,β-unsaturated aldehydes were successfully converted to α-arylcyclohexeneones in 34-67% yield, 10:1-100:0 , and 81-99% . The scalability of this methodology by a gram-scale synthesis and their utility by converting the product to the corresponding epoxide, alcohol, and diol are demonstrated.
View Article and Find Full Text PDFOrganocatalyst-mediated asymmetric one-pot/two domino/three-component coupling reactions for the synthesis of -hydrindanes.
Chem Sci
April 2024
Department of Chemistry, Graduate School of Science, Tohoku University Sendai 980-8578 Japan
Highly substituted -hydrindanes were synthesized by the three-component coupling reactions of 1,3-diethyl 2-(2-oxopropylidene)propanedioate and two different α,β-unsaturated aldehydes catalyzed by diphenylprolinol silyl ether. The reaction proceeds two successive independent catalytic domino reactions in a one-pot reaction by a single chiral catalyst. Domino reactions involve Michael/Michael and Michael/aldol reactions to afford -hydrindanes with excellent diastereoselectivity and nearly optically pure form.
View Article and Find Full Text PDFOrganocatalytic Asymmetric Vinylogous Michael Addition of Electron-Deficient Aryl Alkane Nucleophiles to Enals.
J Org Chem
December 2023
College of Chemical and Pharmaceutical Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China.
We report herein a protocol for an organocatalyzed asymmetric vinylogous Michael addition of aryl alkane nucleophiles with enals under base- and additive-free conditions. A series of allylic building blocks were obtained in 60%-93% yield and 88-99% ee with 20 mol % diphenylprolinol silyl ether as catalyst. This protocol has advantages such as excellent chemoselectivity and regioselectivity, good tolerance of functionalities, and simple reaction conditions.
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