Chiral contact ion-pair catalysis with particular focus on metal-free processes is gaining in interest. As a result, new perspectives are opened, and highly stereoselective transformations, traditionally performed under metal catalysis, can be realized. Herein, we report the development of an unprecedented asymmetric Brønsted acid-catalyzed allylic alkylation. The concept relies chiral which organic counteranion carbocation induces high enantioselectivities allows access to biologically...

Abstract Racemic cyclopropyl ketones undergo enantioselective rearrangement to deliver the corresponding dihydrofurans in presence of a chiral phosphoric acid as catalyst. The reaction involves activation donor‐acceptor cyclopropane substrate by Brønsted catalyst promote ring‐opening event, thus generating carbocationic intermediate that subsequently undergoes cyclization. Computational studies and control experiments support this mechanistic pathway.

A catalytic enantioselective synthesis of dihydrofurans has been developed. 1,3-Dicarbonyl derivatives react with (E)-β,β-bromonitrostyrenes in the presence a chiral bifunctional thiourea catalyst providing mild and efficient access to diverse polysubstituted good yields enantioselectivities.

Benzopyrylium ylides generated in situ from 1-acetoxyisochroman-4-ones reacted with α,β-unsaturated aldehydes the presence of a bifunctional secondary-amine/squaramide catalyst to furnish [5+2] cycloaddition products good yield high diastereo- and enantioselectivity. The reaction proceeds by dienamine activation involves β,γ-functionalization enal. intermediates showed exclusive β,γ-reactivity provided direct access compounds 8-oxabicyclo[3.2.1]octane framework. ability engage...

An easy and straightforward procedure has been developed for the synthesis of highly enantioenriched pyrrolo[1,2-a]quinolines through a one-pot process that comprises domino cyclopropane ring opening/aza-Michael/aldol reaction followed by acid-promoted lactamization. The key feature synthetic approach relies on ability conveniently functionalized cyclopropaneacetaldehydes to undergo organocatalytic activation chiral secondary amine enables catalytic generation donor–acceptor cyclopropane....

Donor-acceptor monosubstituted hydrazones participate as suitable reagents able to undergo an enantioselective formal diaza-ene reaction with α,β-unsaturated aldehydes under chiral secondary amine catalysis. This constitutes a new approach for the conjugate addition of enals metal-free conditions and leads formation γ-hydrazono carboxylic acids after oxidation/[1,3]-H shift. The methodology is also useful synthesis enantioenriched β-substituted α-keto-1,5-diesters by using hydrazone moiety...

BINOL-based N-trifluoromethanesulfonyl phosphoramides catalyze the enantioselective (4+3) cycloaddition between furans and oxyallyl cations, latter being generated in situ by oxidation of allenamides. The chiral organic phosphoramide counteranion is proposed to engage activation cation intermediate through cooperative hydrogen-bonding ion-pairing interactions, enabling an efficient chirality transfer that provide final adducts with high diastereo- enantioselectivities. Remarkably, reaction...

Abstract We have developed a procedure for the stereoselective and diastereodivergent synthesis of densely functionalised cyclohexanes containing four stereocentres through an asymmetric Michael‐initiated ring closure (MIRC) cascade reaction employing hydrogen‐bond catalysis, which is able to prepare adducts with different absolute configurations starting from same materials. The overall process involves highly diastereo‐ enantioselective Michael/Henry between wide range nitroalkenes...

The asymmetric organocatalytic aza-Michael reaction of several nitrogen heterocycles and α,β-unsaturated aldehydes has been studied in detail; under the optimised conditions, conjugate addition products have obtained high to excellent enantioselectivities.

Racemic 5-acyloxydihydropyranones react with enolizable α,β-unsaturated aldehydes in the presence of a chiral secondary amine catalyst furnishing wide range differently substituted tetrahydro-1H-isochromanes excellent results. The reaction relies on activation enal by through formation dienamine intermediate, which undergoes Diels–Alder/elimination cascade reaction. Moreover, overall transformation also results highly efficient dynamic kinetic resolution process, final adducts high yields...

A direct catalytic azidation of primary, secondary, and tertiary allylic alcohols has been developed. This new reaction affords the corresponding azides in high to excellent yields regioselectivities. The provides straightforward access that are valuable intermediates organic synthesis, including preparation primary amines or 1,2,3-triazole derivatives.

The use of chiral N-heterocyclic carbenes (NHCs) as catalysts in asymmetric synthesis has opened a wide range applications due to their unique ability generate reaction intermediates with unusual reactivity patterns that very often involve the reversal typical polarity associated functional groups present starting materials. In this sense, direct activation aldehydes or surrogates by these reactive species provides different chemical structures (conjugated Breslow intermediates, azolium...

Abstract Formylcyclopropanes undergo activation in the presence of an N‐heterocyclic carbene catalyst generating a donor‐acceptor cyclopropane intermediate with ability to ring‐opening followed by formal [4+2] cycloaddition alkylideneoxindoles. This enables direct enantio‐ and diastereoselective synthesis tetrahydropyrano[2,3‐ b ]indoles through use chiral NHC catalyst. magnified image

Abstract The enantioselective synthesis of α‐ and γ‐tocopherol (the most biologically active members vitamin E family) analogues has been accomplished employing a new gold catalyzed intramolecular allylic alkylation reaction followed by an olefin cross‐metathesis as key steps. methodology proved to be applicable different olefins highlighting its potential for the diverse libraries.

Abstract Racemic cyclopropyl ketones undergo enantioselective rearrangement to deliver the corresponding dihydrofurans in presence of a chiral phosphoric acid as catalyst. The reaction involves activation donor‐acceptor cyclopropane substrate by Brønsted catalyst promote ring‐opening event, thus generating carbocationic intermediate that subsequently undergoes cyclization. Computational studies and control experiments support this mechanistic pathway.

Catalytic and enantioselective approaches to transannular reactions are very limited mostly based on chiral Lewis acid catalyzed pericyclic reactions. In this report, we present an efficient straightforward methodology access bicyclic carbo- heterocyclic scaffolds combining different ring sizes through Morita–Baylis–Hillman reaction by a enantiopure bifunctional phosphine. The is remarkably wide in scope enables the use of variety medium large size ketoenone substrates leading final products...

The organocatalytic conjugate addition of different aldehydes to beta-nitroacrolein dimethyl acetal, generating the corresponding highly functionalized nitroaldehydes in high yields and with stereoselectivities, has been studied detail. These transformations have achieved by using both readily available starting materials a 1:1 ratio as well commercially catalysts at 10 mol % catalyst loading. Furthermore, very short efficient protocol devised for preparation enantioenriched pyrrolidines...

The catalytic enantioselective aza-Michael reaction is an important transformation in organic chemistry, which has been used for the synthesis of a significant amount nitrogen-containing products many research areas chemistry. In this review, we summarize literature dealing with versions transformation, where small chiral molecule does not contain metal atoms within its structure (the organocatalyst) employed promoting and also controlling stereochemical outcome. Several examples...

Ethyl glyoxylate N-tosylhydrazone has been identified as an excellent sulfonyl anion surrogate in the DBU-catalyzed conjugate addition reaction with enones and enals for synthesis of functionalized sulfones. The proceeds under base-catalyzed conditions provides a direct access to γ-keto- γ-hydroxy sulfones simple reliable way through sulfa-Michael that high yield chemoselectivity.

A straightforward procedure to carry out the enantioselective benzoin reaction between aldehydes and ynones by employing a chiral N-heterocyclic carbene (NHC) as catalyst was developed. Under optimized conditions, these undergo clean selective 1,2-addition with catalytically generated Breslow intermediate, not observing any byproduct arising from competitive Stetter-type reactivity. This allows preparation of tertiary alkynyl carbinols highly enantioenriched materials, which have remarkable...

Organolithium reagents undergo highly regio- and diastereoselective 1,4-addition to (S,S)-(+)-pseudoephedrine enamides furnishing the corresponding beta-alkyl-substituted adducts in excellent yields diastereoselectivities. In addition, intermediate lithium enolates generated after conjugate addition step a alkylation reaction, alpha,beta-dialkyl-substituted amides high yields. The obtained have been converted into chiral nonracemic beta-alkyl- carboxylic acids gamma-alkyl-...

Abstract Unconjugated 2,5‐dienals are more reactive substrates than the corresponding fully conjugated α,β,γ,δ‐unsaturated aldehydes towards organocatalytic activation through trienamine intermediates. This difference in reactivity has been demonstrated Diels–Alder reaction with nitroalkenes, a that proceeds clean β,ε‐selectivity to afford final products high yields and stereoselectivities, related polyconjugated 2,4‐dienals being completely unreactive.