An enantioselective intramolecular allylic C–H oxidation to generate optically active chromans has been accomplished under the cooperative catalysis of a palladium complex of chiral phosphoramidite ...ligand and 2-fluorobenzoic acid. Mechanistic studies suggest that this reaction commences with a Pd-catalyzed allylic C–H activation event and then undergoes asymmetric allylic alkoxylation. The synthetic significance of the method has been embodied by concisely building up a key chiral intermediate to access (+)-diversonol.
By design: New chiral bis(betaine)s, for example 1, containing two catalytically active centers have been designed. They have proven to be promising organocatalysts for the direct Mannich‐type ...reaction of azlactones with a broad spectrum of aliphatic imines, thus affording α‐tetrasubstituted α,β‐diamino acid surrogates with excellent enantioselectivities.
An enantioselective carbonyl allylation of aldehydes with simple alkenes has been achieved via a one-pot protocol consisting of a Pd-catalyzed allylic C–H borylation with bis(pinanediolato)diboron ...and a chiral Brønsted acid catalyzed asymmetric allylborylation, delivering homoallylic alcohols in high yields and with excellent diastereo- and enantioselectivities. The double chiral induction of chiral allylic borate and chiral phosphoric acid allows the reaction to give excellent stereoselectivities.
Indole and its structural analogues have been frequently found in numerous alkaloids, pharmaceutical products and related materials. The enantioselective construction of these structures allows ...efficient total synthesis of optically pure indole alkaloids, and hence has received worldwide interest. In the past decade,asymmetric organocatalysis has been recognized as one of the most powerful strategies to create chiral molecules with high levels of stereoselectivity. In particular, organocatalytic asymmetric cascade reactions often occur with multiple bond-breaking and forming events simultaneously or sequentially, leading to the appearance of various straightforward approaches to access core structures for asymmetric total synthesis.This review will summarize recent applications of asymmetric organocatalysis in the enantioselective synthesis of indole alkaloids.
A Brønsted acid catalyzed three-component asymmetric 1,3-dipolar addition reaction between aldehydes, amino esters, and dipolarophiles by a new bisphosphoric acid, derived from the linked BINOL, ...furnished multiply substituted pyrrolidines in high yield with excellent enantioselectivities under mild conditions.
Externally yours: 2,3‐Dihydroquinolin‐4(1H)‐ones are obtained in moderate to good yields (40–84 %, see scheme) in a metal‐free oxidation/C(sp3)H functionalization of unactivated aryl alkynes. ...2,6‐Dichloropyridine‐N‐oxide is used as an external oxidant. In the reaction, a Brønsted acid, not a metal, plays a key role in the triple CC bond activation.
Cyclopentenones are synthetically versatile structures, and their straightforward construction from alkynone substrates by employing synthetically streamlining C–H insertion is conceptually appealing ...and of high synthetic potential. But, its implementation is very limited. Herein we report a Au-catalyzed version, which affords 2-bromocyclopent-2-en-1-ones with a broad scope and synthetically desirable diastereoselectivities. The proposed key intermediate capable of the observed insertion into unactivated C–H bonds is a fully functionalized gold vinylidene, which is generated via a novel intermolecular strategy. This flexible access of likely gold vinylidenes opens various opportunities to explore their versatile reactivities.
A Pd‐catalyzed cascade C−H functionalization/asymmetric allylation reaction with aryl α‐diazoamides and allenes has been developed. The reaction provides an efficient approach to construct chiral ...3,3‐disubstituted oxindole derivatives in high levels of yield and enantioselectivity (up to 93 % ee). Notably, the chromium complex works as Lewis acid to facilitate the formation of palladium carbene and to enhance acidity of carboxylic acid, allowing for higher stereochemical control and efficiency.
An achiral Lewis acid enables chiral palladium complex‐catalyzed cascade C−H functionalization/asymmetric allylation reaction of aryl α‐diazoamides and allenes to give synthetically useful chiral 3,3‐disubstituted oxindole derivatives in enhanced yield and enantioselectivity (up to 93 % ee).
Amine/Pd(II) cooperative catalysis has enabled a highly enantioselective addition of cyclic ketones to unactivated alkenes. The hallmark of the strategy includes amide-directed, regioselective ...activation of alkenes by Pd(II) and enhancing the nucleophilicity of α-carbon of the ketones by enamine catalysis to synergistically drive the reaction, which is basically unable to be accessed by a single catalyst. The combination of a commercially available Pd(II) catalyst and diphenylprolinol was able to provide the γ-addition products with good to high yields and efficient stereochemical control (up to 95% ee).
Relay catalysis: An unprecedented protocol for the synthesis of cyclic aminals has been realized under the relay catalysis of a gold(I)/Brønsted acid binary system to generate cyclic aminals in ...excellent yields of up to 99 % with moderate to high diastereoselectivity (see scheme; up to 95:5 d.r.).
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