Access to 2-pyridinones comprising enaminonitriles via AgOAc promoted cascade reactions of thioesters with aminomethylene malononitriles

The facile synthesis of 2-pyridinones containing enaminonitriles from thioesters with aminomethylene malononitriles is achieved through an AgOAc-promoted acylation/cyclization/tautomerization cascade reaction. Control experiments reveal that AgOAc acts as a versatile promoter, activating both thioester and cyano groups while also serving as a Brønsted base in the cascade sequence. Moreover, 2-pyridinones were transformed into biologically significant 2-pyridinone-fused 2-pyrimidones with intriguing fluorescence emission properties.

A base-mediated aerobic oxidative synthesis of cyclopent-2-enol derivatives from doubly activated cyclopropanes and substituted acetonitriles

We report here that polysubstituted cyclopent-2-enols can be constructed by the one-pot reaction of doubly activated cyclopropanes and α-EWG substituted acetonitriles under mild basic conditions via a domino-ring-opening-cyclization/deacylation/oxidation sequence. Moreover, the synthetic applications of these cyclopent-2-enols have been demonstrated in the late-stage derivatization into functionalized cyclopentapyrimidin-4-ones and 2-hydroxy cyclopentanones with good yields.

Synthesis of α-substituted indolylacetamide using acetonitriles as acetamide enolate equivalents through O-transfer reactions

We introduce readily available ammonium hemiaminals as O-transfer reagents and commercially available acetonitriles as a primary amide enolate precursor. The combination serves as an amide enolate equivalent, thereby providing one-pot access to α-substituted indolylacetamides. A broad substrate scope and good functional group tolerance as well as gram-scale synthesis make this protocol highly attractive. Mechanistic experiments suggest that the cyano group is trapped by a hydroxy group of hemiaminals en route to the desired primary amides under metal-free conditions.

Recent advances in ring-opening of donor acceptor cyclopropanes using C-nucleophiles

Ring-opening transformations of donor-acceptor cyclopropanes (DAC) with carbon-centered nucleophiles is a simple, straight-forward approach to 1,3-bifunctional compounds that has witnessed remarkable progress over the past several years. To date, different reactivity patterns of DACs have been successfully exploited in racemic/stereoselective syntheses of various acyclic compounds or carbocycles with an impressive structural diversity. The thriving strategies have been successfully utilized in multistep synthesis of complex target molecules. Herein, the recent advances (2015-present) in the ring-opening of DAC involving electron rich arenes and indoles, active methylene compounds, various dipolarophiles, organoborates/boronates, vinyl ethers etc. following Friedel-Crafts alkylation, annulation/formal cycloaddition reaction, organocatalytic reaction, Nazarov cyclisation etc. are presented.

Temperature controlled condensation of nitriles: efficient and convenient synthesis of β-enaminonitriles, 4-aminopyrimidines and 4-amidinopyrimidines in one system

A wide variety of β-enaminonitriles, 4-aminopyrimidines and 4-amidinopyrimidines were simply synthesized from organonitriles by controlling the reaction temperature.

Utilization of nitriles as the nitrogen source: practical and economical construction of 4-aminopyrimidine and β-enaminonitrile skeletons

A highly practical and economical method for the synthesis of 4-aminopyrimidines and β-enaminonitriles from mixed organonitriles is reported.

Unprecedented formation of 3-(tetrahydrofuran-2-yl)-4H-chromen-4-one in a reaction between 3,3a-dihydro-9H-furo[3,4-b]chromen-9-one and malononitrile

Chromone skeletons are widespread among natural products as well as bioactive molecules. Here, we describe an unprecedented reaction of furo[3,4-b]chromen-9-one with malononitrile to afford 3-(tetrahydrofuran-2-yl)-4H-chromen-4-ones. Experimental data suggest that a sequence of Michael/retro-Michael/nucleophilic addition is involved in this unprecedented transformation.

Diastereoselective Intramolecular [3 + 2]-Annulation of Donor-Acceptor Cyclopropane with Imine-Assembling Hexahydropyrrolo[3,2-c]quinolinone Scaffolds

An intramolecular [3 + 2]-annulation of amide-linked donor-acceptor cyclopropane with in situ-generated imine is described. As a result, diverse hexahydropyrrolo[3,2-c]quinolinones, as the tricyclic core of martinellines, were efficiently assembled in good to excellent yield (up to 93%) with a good diastereomeric ratio (up to 98:2).

Stereospecific Synthesis of 2-Iminothiazolidines via Domino Ring-Opening Cyclization of Activated Aziridines with Aryl- and Alkyl Isothiocyanates

Lewis acid catalyzed domino ring-opening cyclization of activated aziridines with aryl and alkyl isothiocyanates has been accomplished leading to the formation of a wide variety of highly substituted and functionalized 2-iminothiazolidines with excellent diastereo- and enantiospecificity (de, ee up to >99%). The reaction proceeds via a Lewis acid catalyzed SN2-type ring-opening of the activated aziridine followed by a concomitant 5-exo-dig cyclization in a domino fashion to furnish the 2-iminothiazolidine derivative in excellent yields (up to 99%).

An efficient construction of N,N-bicyclic pyrazolidinones comprising enaminonitriles via asymmetric [3+2] cycloaddition

The first thiourea catalysed asymmetric [3+2] cycloaddition reaction between azomethine imines and malanonitriles was devoloped.

Amide-assisted intramolecular [3+2] annulation of cyclopropane ring-opening: a facile and diastereoselective access to the tricyclic core of (±)-scandine

The amide-linked intramolecular [3+2] annulation of cyclopropane ring-opening has been developed to rapidly and diastereoselectively install the tricyclic dihydroquinolinone core of (±)-scandine.

Brönsted acid-mediated annulations of 1-cyanocyclopropane-1-carboxylates with arylhydrazines: efficient strategy for the synthesis of 1,3,5-trisubstituted pyrazoles

A diversity-oriented synthesis of 1H-pyrazole derivatives via Brönsted acid-promoted annulations of 1-cyanocyclopropane-1-carboxylates with arylhydrazines has been developed.

Carbocycles from donor–acceptor cyclopropanes

Donor–acceptor cyclopropane annulations – not just for heterocycles.

Efficient strategy for construction of 6-carbamoylfulvene-6-carboxylate skeletons via [3 + 2] cycloaddition of 1-cyanocyclopropane 1-ester with β-nitrostyrenes

An efficient and straightforward the preparation of 6-carbamoylfulvene-6-carboxylates via a cycloaddition reaction between 1-cyanocyclopropane 1-ester and β-nitrostyrenes.

Yb(OTf)3 catalyzed [3 + 2] annulations of D–A cyclopropanes with β-oxodithioesters: a regioselective synthesis of tetrahydrothiophenes

An efficient approach to synthesis tetrahydrothiophenes was developed through the reaction of β-oxodithioesters and D–A cyclopropanes catalyzed by Yb(OTf)₃. This methodology was highly regioselective.

Lewis acid catalyzed (3 + 2)-annulations of donor-acceptor cyclopropanes and ynamides

The Sc(OTf)3-catalyzed (3 + 2)-annulation of donor-acceptor cyclopropanes and ynamides is described, providing the corresponding cyclopentene sulfonamides in good to excellent yield. Deprotection and hydrolysis of the resulting ensulfonamides delivers 2,3-substituted cyclopentanones with high diastereoselectivity.