Base-Promoted and Copper(I)-Catalyzed Tandem Cyclization-C(sp)-N Coupling of Vinyl Malononitriles with -Nitrochalcones: Access to Acridones and their Fused Derivatives.

An efficient CsCO-promoted and copper(I)-catalyzed double cyclization of -nitrochalcones with vinyl malononitriles for the access to a variety of tri- and tetra-substituted acridones and their fused derivatives with a value-added CN group has been developed for the first time. This one-pot operation proceeds through a Michael-cyclization-aromatization, followed by regioselective -amination via nucleophilic aromatic substitution (SAr) reaction, resulting in two C═C bonds and a C-N bond for acridone ring synthesis. This economic strategy based on 100% carbon atoms ensures the successive formation of two rings in a one-pot operation, good to high yields, a wide range of substrates, and good tolerance of functionalities.

Robust Organocatalytic Three-Component Approach to 1,3-Diarylallylidene Pyrazolones via Consecutive Double Condensation Reactions.

A robust pyrrolidine-BzOH salt-catalyzed one-pot three-component reaction involving 4-unsubstituted pyrazolones, aryl/heteroarylaldehydes, and aryl methyl ketones is reported for the first time. This catalytic process fortifies an efficient method, allowing for the practical synthesis of a wide array of synthetically useful 1,3-diarylallylidene pyrazolones in good to high yields exclusively in their single geometrical isomer forms. Furthermore, this catalyst facilitates a sequential double condensation reaction under thermal conditions, thereby enabling two consecutive C═C bonds through displacement of aryl groups.

Copper(I)-Photocatalyzed Diastereoselective Aziridination of N-Sulfonyl Imines with Vinyl Azides: Application to Benzo[f][1,2,3]oxathiazepines Dioxides and Fused Isoxazolines.

An in situ generated photoactive copper(I)-complex-catalyzed aziridination reaction of cyclic N-sulfonyl imines with α-aryl-substituted vinyl azides irradiated by blue-LEDs light is reported for the first time. This novel SET process represents a mild, sustainable, and pragmatic method for accessing synthetically resourceful sulfamidate-fused aziridines in acceptable chemical yields with excellent diastereoselectivities. Delightedly, pharmacologically attractive benzo[f][1,2,3]oxathiazepine dioxides and fused isoxazoline frameworks were achieved through our newly developed metal-free based ring-expansion techniques, highlighting the synthetic value of accessed aziridines.

Base-promoted cyclization of -hydroxyacetophenones with generated cyclopropenes: diastereoselective access to spirobenzo[]oxepines and related precursors.

An unprecedented [5 + 2] spirocyclization route to obtain a vital class of functionalized spirobenzo[]oxepine-cyclopropanes in good to high yields with excellent diastereoselectivities is reported. This domino reaction proceeds through a regioselective oxa-Michael addition of -hydroxyacetophenones as 1,5-binucleophiles to produced highly reactive cyclopropenes from 2-aroyl-1-chlorocyclopropanecarboxylates triggered by CsCO and the subsequent intramolecular aldol reaction under heating conditions, enabling the formation of new C-O and C-C bonds for benzo[]oxepine ring synthesis. Moreover, at ambient temperature, the above C-O/C-C bond-forming event takes place preferentially a [4 + 2] annulation path over a spirocyclization route, leading to substituted fused-cyclopropanes with good diastereoselectivities.

Swapping Copper-Catalytic Process: Selective Access to Pyrazoles and Conjugated Ketimines from Oxime Acetates and Cyclic Sulfamidate Imines.

A powerful CuCl-catalyzed sequential one-pot reaction of aryl methyl ketoxime acetates with cyclic N-sulfonyl imines followed by elimination in the presence of base is reported. This hydrazine-free method conveniently makes C-C and N-N bonds via a radical cleavage of the N-O bond, delivering a special class of C3-hydroxyarylated pyrazoles in good yields. Surprisingly, while employing CuI as a catalyst instead of CuCl, the reaction proceeds through a non-radical pathway which embodies a new tactic for the high-yielding access to value-added conjugated N-unsubstituted ketimines.

Regioselective access to di- and trisubstituted pyridines a metal-oxidant-solvent-free domino reaction involving 3-chloropropiophenones.

A remarkable metal-oxidant-solvent- and base-free domino route for regioselective access to a wide range of 2,4-di- and 2,3,4/6-trisubstituted pyridines including carbo- and heterocyclic fused pyridines is reported. This [3C + 2C + 1N] cyclization reaction occurs between 3-chloropropiophenones (3C units), enolizable acyclic/cyclic ketones (2C sources) and NHOAc as a robust N source under neat conditions under an open atmosphere, producing new C=C and C=N-C bonds in highly chemo- and regioselective manners. Interestingly, this eco-friendly method has many positive features: excellent functional group tolerance, broad substrate scope, good to excellent regioselectivities, promising yields, no-unwanted products, neutral reaction conditions and appropriateness for large-scale synthesis.

A substrate-dependent reaction of 1-aryl-2-alkyl-1,2-diketones with 2-aroyl-1-chlorocyclopropanecarboxylates: selective access to 2',5'-dicyclopropoxy-1,1':4',1''-teraryls and pentafulvenes.

An interesting substrate-controlled one-pot approach to highly substituted 2',5'-dicyclopropoxy-1,1':4',1''-teraryls and 6-hydroxypentafulvenes involving various 1,2-diketones and 2-aroyl-1-chlorocyclopropanecarboxylates as 3C Michael acceptors triggered by CsCO has been developed. We noticed that 1,2-diketones play a decisive role in this reaction to determine the product's selectivity. For example, aryl rings having electron-poor functionalities at the and -positions of 1,2-diketones led to 2,5-diarylhydroquinones selectively a cyclodimerization/double oxa-Michael process with highly strained cyclopropenes.

Cu(OAc)/DABCO-mediated domino reaction of vinyl malononitriles with cyclic sulfamidate imines: access to 6-hydroxyaryl-2-aminonicotinonitriles.

A novel Cu(II)-salt/DABCO-mediated one-pot access to a myriad of highly substituted biologically relevant 2-aminonicotinonitriles possessing a resourceful phenolic moiety with satisfactory yields is reported. This method involves cyclic sulfamidate imines as 1C1N sources and different kinds of acyclic/cyclic vinyl malononitriles as 4C sources for pyridine synthesis a vinylogous Mannich-cycloaromatization sequence process, creating two new C-N bonds under mild conditions. Importantly, this strategy is applicable to gram-scale syntheses, underlining the method's practicability and allowing for a wide range of substrates with excellent functional group tolerance.

Unmasking the reverse reactivity of cyclic -sulfonyl ketimines: multifaceted applications in organic synthesis.

The chemistry related to the exploration of cyclic -sulfonyl ketimines and their derivatives has attracted significant attention in the last few decades because of their intriguing structures and properties. They serve broadly as reactive synthons in various reactions to create a diverse set of synthetically and biologically attractive molecules. Furthermore, these moieties, which possess multiple heteroatoms (N, O and S), display or can enhance many biological activities.

Diastereoselective desymmetrization reactions of prochiral para-quinamines with cyclopropenes generated in situ: access to fused hydroindol-5-one scaffolds.

Interesting desymmetric [3 + 2] annulation reactions between p-quinamines as prochiral N-donors and 2-aroyl-1-chlorocyclopropanecarboxylates facilitated by a base are reported. This successive double Michael reaction delivered a unique class of cyclopropane-fused hydoindol-5-one frameworks, each having four contiguous stereogenic centers, with three of them being fully substituted. Moreover, this method was found to provide acceptable chemical yields with promising diastereoselectivities (dr of up to ≤95 : 5) and to work with a variety of substrates.

Substrate-Controlled Domino Reaction of -Sulfonyl Ketimines with 2-Aroyl-1-chlorocyclopropanecarboxylates: Access to Cyclopenta[]chromenes and Benzo[]cyclopenta[][1,2]thiazepine Dioxides.

An unprecedented substrate-controlled annulation method for the synthesis of fascinating classes of angularly fused cyclopenta[]chromenes and benzo[]cyclopenta[][1,2]thiazepine 5,5-dioxide derivatives in good to high chemical yields is reported. This Michael-initiated ring-expansion reaction would enable two C-C and one C-O or C-N bonds by a judicious choice of carbonucleophiles, either 4-alkyl or 3-alkyl-substituted -sulfonyl ketimines, respectively, with a series of donor-acceptor cyclopropane scaffolds as 4C sources promoted by DBU. Moreover, this eco-friendly method is mild enough to protect different kinds of functionalities.

1,6-Addition of vinyl p-quinone methides with cyclic sulfamidate imines: access to 4-hydroxyaryl-2,6-diarylpyridines.

A simple and powerful one-pot regioselective 1,6-addition elimination-6π-aza-electrocyclization-aromatization reaction of vinyl/dienyl-substituted para-quinone methides with a bunch of cyclic sulfamidate imines as 2C1N synthons promoted by DABCO as a solid organobase in an open atmosphere is reported for the first time. The above-mentioned C-C and C-N bond formation process provides good to high yields of a wide range of symmetrically and unsymmetrically 2,4,6-trisubstituted pyridines possessing a sterically hindered phenolic moiety at the C4-position with a broad substrate scope. This domino [3 + 3] cyclization reaction gives rise to several compatible functionalities under metal-free conditions.

NHOAc-Promoted Domino Route to Hydroxyarylated Unsymmetrical Pyridines under Neat Conditions.

A new metal-, oxidant-, and solvent-free ecofriendly domino method has been established for modular synthesis of a diverse range of medicinally promising hydroxyarylated unsymmetrical pyridines in good to high chemical yields with an excellent regioselectivity. This domino process involves a range of -sulfonyl ketimines as C,N-binucleophiles, enolizable ketones, and aromatic/heteroaromatic aldehydes using ammonium acetate as an ideal promoter under neat conditions, which creates two new C-C bonds and one C-N bond. Notably, the neutral reaction conditions are mild enough to tolerate a range of functionalities and cover a variety of substrates, thus bestowing a powerful avenue to access tri- and tetrasubstituted pyridines including carbo- and heterocyclic fused ones.

Rationally designed small molecules targeting toxic CAG repeat RNA that causes Huntington's disease (HD) and spinocerebellar ataxia (SCAs).

Huntington's diseases (HD) is a very devastating disease caused by r(CAG) expansion in HTT gene, encoding the huntingtin protein. r(CAG) expansion causes disease via multiple pathways including, 1) loss of normal protein function like sequestration of RNA binding protein such as Muscleblind-like (MBNL) and nucleolin, 2) Gain of function for mutant proteins and 3) repeat-associated non-ATG (RAN) translation; in which expanded r(CAG) translates into toxic poly glu, poly ser, or poly ala without the use of any canonical start codon. Herein, we have rationally designed and synthesized a unique class of pyridocoumarin derivatives that target the r(CAG) involved in HD and spinocerebellar ataxia (SCA) pathogenesis.

Chemoselective cyclization of N-sulfonyl ketimines with ethenesulfonyl fluorides: access to trans-cyclopropanes and fused-dihydropyrroles.

An interesting stereo- and chemoselective cyclization reaction of several N-sulfonyl ketimines as C/N-donors with a variety of α,β-unsaturated sulfonyl fluorides promoted by DBU is reported. This substrate-dependent selective C-C vs. C-N bond cyclization process leads to important classes of trans-cyclopropane and fused dihydropyrrole scaffolds in satisfactory yields with excellent diastereoselectivities (dr up to ≤99 : 1).

DABCO- and DBU-promoted one-pot reaction of -sulfonyl ketimines with Morita-Baylis-Hillman carbonates: a sequential approach to (2-hydroxyaryl)nicotinate derivatives.

An intriguing DABCO-catalyzed and DBU-promoted one-pot synthesis of an important class of (2-hydroxyaryl)pyridine derivatives bearing a carboxylate or a nitrile group suitably placed at C3 position of the aza-ring has been achieved in acceptable chemical yields with a broad functional group tolerance. This sequential C-C/C-N bond making process proceeds through a regioselective allylic alkylation/aza-Michael reaction between MBH carbonates derived from an acrylate/acrylonitrile and -sulfonyl ketimines as C,N-binucleophiles catalyzed by DABCO, followed by elimination of SO under the influence of base and subsequent aromatization in an open atmosphere.

Stereoselective Synthesis of 3,3-Disubstituted Oxindoles and Spirooxindoles via Allylic Alkylation of Morita-Baylis-Hillman Carbonates of Isatins with Cyclic Sulfamidate Imines Catalyzed by DABCO.

An efficient, organocatalytic, and ecofriendly method has been developed for the quick construction of a wide array of 3,3-disubstituted oxindoles in good to excellent yields and diastereomeric ratio (up to ≤96:4) with excellent functional group tolerance via an allylic alkylation reaction of cyclic sulfamidate imines with a number of MBH carbonates of isatins in 2-MeTHF as an environmentally benign solvent at room temperature using 5 mol % of DABCO. Furthermore, a metal-free-based one-shot synthesis of a medicinally promising polycyclic spirooxindole with an all-carbon spirocenter has been achieved with outstanding dr value (up to ≤99:1).

Metal- and Solvent-Free Approach to Diversely Substituted Picolinates via Domino Reaction of Cyclic Sulfamidate Imines with β,γ-Unsaturated α-Ketocarbonyls.

An efficient, solvent-free, and eco-friendly domino reaction of 5/6-membered cyclic sulfamidate imines with a variety of β,γ-unsaturated α-ketocarbonyls in neat conditions under MW irradiation promoted by DABCO as a solid organobase has been developed for the rapid construction of a novel class of densely functionalized picolinates. This interesting metal-solvent-free tactic allows a wide range of useful functionalities on the aryl rings and delivers good to excellent yields of the aforesaid aza-heterocycles within short time spans (20-40 min). A biologically promising imidazo[1,2-a]pyridine was successfully synthesized through our unique procedure.

Domino reaction of cyclic sulfamidate imines with Morita-Baylis-Hillman acetates promoted by DABCO: a metal-free approach to functionalized nicotinic acid derivatives.

A facile, green, metal-free new one-pot synthetic strategy has been developed for easy access to a wide array of medicinally promising functionalized pyridines having an ester, a nitrile or an acetyl group at the C-3 position in good to excellent yields via a domino S2/elimination/6π-aza-electrocyclization/aromatization reaction of several 4-aryl/hetero-aryl-substituted 5-membered cyclic sulfamidate imines with a broad range of MBH acetates of acrylate/acrylonitrile/MVK in 2-MeTHF promoted by DABCO as an organobase under an O atmosphere. Moreover, a biologically interesting triazolopyridine derivative was achieved through a unique procedure.

Access to 4,6-Diarylpicolinates via a Domino Reaction of Cyclic Sulfamidate Imines with Morita-Baylis-Hillman Acetates of Nitroolefins/Nitrodienes.

An interesting domino reaction of 5-membered cyclic sulfamidate imines with a variety of Morita-Baylis-Hillman acetates of nitroolefins/nitrodienes in the presence of DABCO as an organic base at 55 °C is reported for the first time. This new synthetic strategy provides a series of pharmacologically interesting 4,6-diarylpicolinates in high to excellent yields and allows several compatible functionalities on aryl rings. Moreover, the biologically interesting imidazo[1,2-a]pyridine (alpidem derivative) has been prepared in high chemical yield through a unique procedure.

DABCO catalyzed domino Michael/hydroalkoxylation reaction involving α-alkynyl-β-aryl nitroolefins: excellent stereoselective access to dihydropyrano[3,2-c]chromenes, pyranonaphthoquinones and related heterocycles.

Excellent stereoselective (up to ≤96 : 4 Z/E ratio) construction of pharmaceutically interesting functionalized pyrano[3,2-c]chromenes, pyranonaphthoquinones and related pyrano-fused heterocycles has been achieved in good to high yields (72-89%) through a domino Michael/hydroalkoxylation reaction involving several enolizable cyclic β-keto esters/1,3-dicarbonyls and α-arylacetylenyl-β-nitrostyrenes as binucleophiles in EtOH at room temperature using DABCO as an organocatalyst. Moreover, syn-2-benzyl-4-aryl-3,4-dihydropyrano[3,2-c]chromenes were obtained in high yields (81-86%) via a stereoselective denitrohydrogenation of the corresponding 2-benzylidene-3,4-dihydropyrano[3,2-c]chromenes using a catalytic amount of 10% Pd/C.

An organocatalytic highly efficient approach to the direct synthesis of substituted carbazoles in water.

A simple, mild, green, catalytic and general procedure for the direct synthesis of highly functionalized 1-methoxycarbonyl-2-aryl/alkyl-3-nitro-9H-carbazoles has been achieved in water medium via a one-pot domino Michael-Henry/aromatization reaction of methyl 2-(3-formyl-1H-indol-2-yl)acetates with aryl/alky-substituted β-nitroolefins under air using DABCO (30 mol%) as an organocatalyst. In addition, the bench scale synthesis can be performed without using toxic organic solvents and a biologically important new fused carbazole has been prepared.

L-proline catalyzed stereoselective synthesis of (E)-methyl-α-indol-2-yl-β-aryl/alkyl acrylates: easy access to substituted carbazoles, γ-carbolines and prenostodione.

A simple, mild and robust method for the stereoselective synthesis of (E)-methyl α-(3-formyl-1H-indol-2-yl)-β-aryl/alkyl-substituted acrylates via a condensation reaction of methyl 2-(3-formyl-1H-indol-2-yl)acetate with several alkyl or aryl aldehydes using L-proline (25 mol%) as a catalyst is presented for the first time. In addition, completely metal free based high yielding methods for the syntheses of highly substituted biologically important carbazoles, γ-carbolines and the marine alkaloid prenostodione have been developed through our methodology.

Organocatalytic enantioselective synthesis of both diastereomers of alpha-hydroxyphosphinates.

Racemic alpha-acylphosphinates and formylphosphinate hydrate were used directly as the substrates in a proline derivative-catalyzed cross aldol reaction with ketones. Because of the preexisting phosphorus stereogenic center, a mixture of two diastereomers of the corresponding alpha-hydroxyphosphinates was obtained in this reaction. Good to high enantioselectivities (up to 99% ee) were obtained simultaneously for the two diastereomers in good yields.

Ethyl [1-(4-bromo-phen-yl)-1-hydr-oxy-3-oxobut-yl](phen-yl)phosphinate monohydrate.

In the title hydrate, C(18)H(20)BrO(4)P·H(2)O, a staggered conformation is found when the organic mol-ecule is viewed down the central P-C bond, with the oxo and hydroxyl groups being diagonally opposite; each of the central P and C atoms has an S-configuration. The crystal structure features supra-molecular double chains along the b axis mediated by O(hydrox-yl)-H⋯O(oxo), O(water)-H⋯O(oxo), and O(water)-H⋯O(water) hydrogen bonds.