Straightforward Access to Pyrazine-(2,3)-diones through Sequential Three-Component Reaction

A novel protocol for the assembly of polysubstituted 2,3-dioxo-1,4,5,6-tetrahydropyrazines and 2,3-dioxo-hydro-1H-cycloalkyl[b]pyrazines has been developed by the sequential three-component reaction of primary aliphatic amines, 1,2-diaza-1,3-dienes (DDs) and oxalyl chloride. This synthetic sequence proceeds by initial aza-Michael addition of the amine to the azo-ene compounds and subsequent ring closure involving the oxalyl chloride. The ready availability of the starting materials as well as the high level of practicability of the reaction and work-up make this approach an attractive opportunity towards these uncommon systems.     

Synthesis of 1-(R-Phenyl)-5-(R-Methyl)-1H-1,2,3-triazole-4-carboxylic Acids by One-Pot Tandem Reaction

Substituted 1H-1,2,3-triazole-4-carboxylic acids were synthesized by a three-component reaction of arylazides, ethyl 4-chloro-3-oxobutanoate, and either O- or S-nucleophiles in the presence of a base catalyst. The reaction most probably proceeded as a [3 + 2] cyclocondensation reaction between arylazide and ethyl 4-chloro-3-oxobutanoate with the further nucleophilic substitution of chlorine in the chloromethyl group. Reaction optimization was performed to carry out the reaction with an O-nucleophile. Conditions were found under which diethyl 2,5-dihydroxyterephthalate (the product of self-condensation of two molecules of ethyl 4-chloro-3-oxobutanoate with the further oxidation by azide) was obtained.     

Asymmetric organocatalytic Biginelli reactions: a new approach to quickly access optically active 3,4-dihydropyrimidin-2-(1H)-ones

The Biginelli reaction, known for over 100 years, is an important multicomponent reaction for accessing dihydropyrimidinones (DHPMs). The individual enantiomers of DHPMs exhibit different or even opposite pharmaceutical activities, which require synthetic methods to easily access the optically pure DHPMs. In recent decades, many efforts have focused on developing procedures for the preparation of optically active Biginelli products. In this article, we will summarize the developments in the synthetic methods to access optically active DHPMs with an emphasis on the recent advances in the asymmetric catalytic Biginelli reactions, along with concepts to design the organocatalytic asymmetric variants.     

2-(Alkylamino)-3-aryl-6,7-dihydrobenzofuran-4(5H)-ones: Improved Synthesis and their Photophysical Properties

Furans are an important class of compounds and exhibit a diverse range of activities and properties. As such, improved synthetic access to furans is an important research goal. In the present report, a solvent- and catalyst-free reaction between 5,5-dimethyl-1,3-cyclohexanedione (dimedone), an aryl aldehyde and an isocyanide under microwave irradiation is presented. This method is significantly improved from previously described protocols in terms of applicability of wide ranging aryl aldehydes, better yields, shorter reaction times, facile work up and essentially no need of column chromatography. The photophysical properties of this series of compounds were studied for their possible applicability in the field of metal ion sensors. In solution, two compounds, 2-(cyclohexylamino)-3-(1H-indol-3-yl)-6,6-dimethyl-6,7-dihydrobenzofuran-4(5H)-one (1 i) and 2-(tert-butylamino)-3-(1H-indol-3-yl)-6,6-dimethyl-6,7-dihydrobenzofuran-4(5H)-one (1 j), underwent an observable color change from yellow to colorless in the presence of aluminum(III) ions. Further studies to investigate the UV absorption and luminescence behavior of these compounds revealed their utility as “naked-eye sensors” for aluminum detection.     

Diastereo‐ and Enantioselective Construction of a Bispirooxindole Scaffold Containing a Tetrahydro‐β‐carboline Moiety through an Organocatalytic Asymmetric Cascade Reaction

The first catalytic asymmetric construction of a new class of bispirooxindole scaffold‐containing tetrahydro‐β‐carboline moiety has been established through chiral phosphoric acid‐catalyzed three‐component cascade Michael/Pictet–Spengler reactions of isatin‐derived 3‐indolylmethanols, isatins, and amino‐ester, which afforded structurally complex and diverse bispirooxindoles with one quaternary and one tetrasubstituted stereogenic centers in excellent stereoselectivities (all >95:5 diastereomeric ratio (d.r.), up to 98:2 enantiomeric ratio (e.r.)). This intriguing class of chiral bispirooxindoles integrated the two important structures of tetrahydro‐β‐carboline and bispirooxindole, both of them possessing significant bioactivities. This approach also combined the merits of asymmetric organocatalysis and multicomponent tandem reaction, which provided a unique strategy for the preparation of structurally rigid bispiro‐architectures with concomitant creation of multiple quaternary stereogenic centers.     

Three-Component Reaction of 1-(Oxyran-2-ylmethyl)-1 H -indole-3-carbaldehyde with CH-Acids and Amines

One-pot synthesis of 3-vinyl substituted indoles containing 1,2-amino alcohol fragment at the nitrogen atom was performed by the reactions of 1-(oxiran-2-ylmethyl)-1H-indole-3-carbaldehyde with methylene-active compounds and amines.     

Simple one-pot multicomponent approach to polyfunctionalized 2-amino-1-methyl-6-(methylthio)-5-nitro-4-aryl-1,4-dihydropyridine-3-carbonitriles

A series of polyfunctionalized 2-amino-1-methyl-6-(methylthio)-5-nitro-4-aryl-1,4-dihydropyridine-3-carbonitriles have been prepared using a multicomponent condensation reaction between aromatic aldehydes, malononitrile, and (Z) N-methyl-1-(methylthio)-2-nitroethenamine in the presence of Et₃N in acetonitrile.     

Acridin-9(10H)-one-based blue thermally activated delayed fluorescence materials: improvement of color purity and efficiency stability

A series of donor-acceptor-donor (D-A-D) type blue thermally activated delayed fluorescence (TADF) emitters, namely, 2,7-DtBuCz-AD, 3,6-DtBuCz-AD, 3,6-DMAC-AD, and 3,6-DMAC-AD-CF₃, were developed with highly rigid acridin-9(10H)-one (i.e. acridone [AD]) as acceptor. The regioisomeric effect study revealed that the attachment of donors at 3,6-sites of AD ring dramatically enhanced TADF ratio in comparison with the 2,7-site isomer. On the one hand, by varying donors from dimethylacridine (DMAC) to tert-butylcarbazole (tBuCz) at 3,6-sites of AD ring, the emission color purity of blue TADF emitters was improved from sky blue to deep blue. On the other hand, by introducing trifluoromethyl (CF₃) onto 9-site phenyl ring of 3,6-DtBuCz-AD, the efficiency stability of the sky blue emission for 3,6-DMAC-AD-CF₃ was remarkably improved. The deep blue organic light-emitting diode (OLED) of 3,6-DtBuCz-AD exhibited a maximum external quantum efficiency (EQE_max) of 17.88% with CIE coordinates of (0.15, 0.08), which is among the best performances ever reported for deep blue TADF-OLEDs. The sky-blue OLED of 3,6-DMAC-AD realized an EQE_max of 23.16%. And with the incorporation of CF₃, the sky blue device of 3,6-DMAC-AD-CF₃ exhibited extremely low efficiency loss of only 5.1% at the high brightness of 1,000 cd/m².     

ZnO Nanoparticles as an Efficient,Heterogeneous, Reusable,and Ecofriendly Catalyst for One-Pot,Three-Component Synthesis of 3,4-Dihydropyrimidin-2(1H)-(thio)one Derivatives in Water

An extremely efficient heterogeneous protocol is reported for the one-pot, three-component synthesis of a series of dihydropyrimidinones (DHPMs) in the presence of ZnO nanoparticles in water as a green solvent. The ZnO nanoparticles exhibited excellent catalytic activity and the proposed methodology is capable of providing the desired products in good yields (65–94%) within short reaction times. After the reaction course, ZnO nanoparticles can be recycled and reused without any apparent loss of activity, which makes this ecofriendly process cost-effective.     

Silver(I)‐Catalyzed Three‐Component Reaction of Propargylic Alcohols,Carbon Dioxide and Monohydric Alcohols: Thermodynamically Feasible Access to β‐Oxopropyl Carbonates

A silver(I)‐catalyzed three‐component reaction of propargylic alcohols, CO₂, and monohydric alcohols was successfully developed for the synthesis of β‐oxopropyl carbonates. As such, a series of β‐oxopropyl carbonates were exclusively produced in excellent yields (up to 98 %), even under atmospheric pressure of CO₂. The silver catalyst works efficiently for both the carboxylative cyclization of propargylic alcohols with CO₂ and subsequent transesterification of α‐alkylidene cyclic carbonates with monohydric alcohols; thus this tandem process performs smoothly under mild conditions. This work provides a versatile and thermodynamically favorable approach to dissymmetric dialkyl carbonates.     

A Palladium(II)‐Catalyzed Synthesis of Spiroacetals through a One‐Pot Multicomponent Cascade Reaction

Functionalized spiroacetals have been easily prepared in a one‐pot three‐component coupling process that involves the reaction of pentynol derivatives, salicylaldehydes, and amines in the presence of catalytic amounts of a palladium(II) complex (see scheme). Alternatively, oxygen‐substituted spiroacetals can be obtained by using orthoesters as the third component.

     

Synthesis and Crystal Structure of 3-Methyl-10-(4-nitrophenyl)-7,8,10,10a-tetrahydropyrano[4,3-b]chromene-1,9(4aH,6H)-dione

The title compound (C19H15NO6) was synthesized via a three-component reaction and characterized by means of IR and 1H NMR. Its crystal and molecular structures were determined by X-ray diffractometry. It belongs to the monoclinic system, space group P21/c with a = 11.670(3), b = 12.076(3), c = 11.613(3), β = 99.490(4)°, V = 1614.2(7)3, Mr = 353.32, Z = 4, Dc = 1.454 g/cm3, λ = 0.71073, μ = 0.110 mm-1, F(000) = 736, the final R = 0.0503 and wR = 0.1311. A total of 8454 reflections were collected, of which 3497 were independent (Rint = 0.0333) and 2102 were observed with I > 2σ(I).     

Scalable total synthesis of (-)-berkelic acid by using a protecting-group-free strategy

Supply chain: the polycyclic core of (-)-berkelic acid (1) was constructed in just one step from very simple starting materials. The total synthesis of 1 involves a seven-step linear sequence. Protection/deprotection steps were avoided and all but the last step were performed on a gram scale. This synthesis could solve the supply problem associated with the exhaustion of the natural source.     

Synthesis of 9-C6H5-3-(π-C5H5)-3,1,2-CoC2B9H10 by cross-coupling reaction of 9-I-3-(π-C5H5)-3,1,2-CoC2B9H10 with C6H5ZnCl catalyzed by palladium complexes

The cross-coupling reaction of 9-I-3-(π-C₅H₅)-3,1,2-CoC₂B₉H₁₀ with organozinc compounds catalyzed by palladium complexes was used to synthesize the first representative ofB-phenyl-substituted carboranes, 9-C₆H₅-3-(π-C₅H₅)-3,1,2-CoC₂B₉H₁₀. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No: 6, pp. 1253–1254, June, 1998.     

Facile Heteropolyacid-Promoted Synthesis of Indeno[1,2-b]quinoline-9,11(6H,10H)-dione Derivatives

An efficient synthesis of indeno[1,2-b]quinoline-9,11(6H,10H)-dione derivatives was reported via four-component coupling reaction of aldehydes, dimedone, 1,3-indandione, and amines in refluxing ethanol or three-component condensation of aldehydes, 1,3-indandione, and 5,5-dimethyl-3-arylamino-cyclohex-2-enone derivatives at 120 °C under solvent-free conditions in the presence of a catalytic amount of Preyssler-type heteropolyacid, H₁₄[NaP₅W₃₀O₁₁₀], as a green and reusable catalyst.     

Rhodium(III)‐Catalyzed Three‐Component Reaction of Imines,Alkynes, and Aldehydes through CH Activation

An efficient rhodium(III)‐catalyzed tandem three‐component reaction of imines, alkynes and aldehydes through C?H activation has been developed. High stereo‐ and regioselectivity, as well as good yields were obtained in most cases. The simple and atom‐economical approach offers a broad scope of substrates, providing polycyclic skeletons with potential biological properties.