SciCombinator

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Concept: Alkyne

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An investigation of the intramolecular cyclopropanation reactions of α-diazo-β-ketonitriles is reported. These studies reveal that α-diazo-β-ketonitriles exhibit unique reactivity in their ability to undergo arene cyclopropanation reactions; other similar acceptor-acceptor-substituted diazo substrates instead produce mixtures of C-H insertion and dimerization products. α-Diazo-β-ketonitriles also undergo highly efficient intramolecular cyclopropanation of tri- and tetrasubstituted alkenes. In addition, the α-cyano-α-ketocyclopropane products are demonstrated to serve as substrates for SN2, SN2', and aldehyde cycloaddition reactions.

Concepts: Alkyne, Alkene, Functional groups, Cycloaddition, Aldehyde, Wittig reaction, Elimination reaction, Cyclopropane

28

An operationally simple approach for the regioselective tandem synthesis of indolo[1,2-a]quinolines 4a-v and pyrrolo[1,2-a]quinolines 5a-k from 1-(2-bromophenyl)-1H-indole/pyrrole/imidazole 1a-c, 2a,b by the palladium-catalyzed sequential C-C bond formation is described. The developed approach involves the palladium-catalyzed Sonogashira coupling followed by the intramolecular C-C bond formation via C-H activation, which leads to the formation of 6-endo-dig cyclized product. This synthetic methodology accommodates wide functional group variation on alkyne, which proves to be advantageous for the structural and biological activity assessments.

Concepts: Chemical reaction, Functional group, Alkyne, Alkene, Organic chemistry, Aldehyde, Carbon-carbon bond forming reactions, Sonogashira coupling

28

Site-selective sequential coupling reactions directed toward bis(diaryl)butadiynes are described. The reaction site could be controlled completely by the on/off application of electricity. The electro-oxidative homo-coupling of terminal alkynes (electricity ON) and the subsequent Suzuki-Miyaura coupling (electricity OFF) afforded bis(diaryl)butadiynes in high yields. The obtained 1,4-bis(diaryl)butadiynes could be converted to a 2,5-bis(diaryl)thiophene derivative, which exhibited blue fluorescence.

Concepts: Michael Faraday, Electric current, Electrochemistry, Alkyne, Heck reaction, Suzuki reaction, Sonogashira coupling, Cadiot-Chodkiewicz coupling

28

Now even terminal: The 2,4,6-trimethylbenzylidyne complexes [MesCM{OC(CF(3) )(2) Me}(3) ] (M=Mo, W) were synthesized from [Mo(CO)(6) ] and [W(CO)(6) ], respectively. The molybdenum complex is an efficient catalyst for the metathesis of internal and terminal alkynes and also for the ring-closing metathesis of internal and terminal α,ω-diynes at room temperature and low catalyst concentrations.

Concepts: Olefin metathesis, Complex, Alkyne, Complexity

28

The [3 + 2] cycloaddition reaction between carbonyl ylides generated from epoxides and alkynes (phenylacetylene, methyl propiolate, methyl but-2-ynoate and methyl 3-phenylpropiolate) to give substituted 2,5-dihydrofurans was investigated. The effect of indium(iii) chloride on the outcome of the reaction was studied in the case of phenylacetylene and methyl propiolate. The thermal reaction between the carbonyl ylide coming from 2,2-dicyano-3-phenyloxirane and both methyl propiolate and methyl but-2-ynoate was theoretically investigated using DFT methods in order to explain the reactivity and regioselectivity observed.

Concepts: Scientific method, Alkyne, Functional groups, Hypothesis, Theory, Cycloaddition, Ylide, Phenylacetylene

27

The performance of well-defined ultrasmall iron(0) nanoparticles (NPs) as catalysts for the selective hydrogenation of unsaturated C-C and C[double bond, length as m-dash]X bonds is reported. Monodisperse iron nanoparticles of about 2 nm size are synthesized by the decomposition of {Fe(N[Si(CH3)3]2)2}2 under dihydrogen. They are found to be active for the hydrogenation of various alkenes and alkynes under mild conditions and weakly active for C[double bond, length as m-dash]O bond hydrogenation.

Concepts: Oxygen, Hydrogen, Hydrogenation, Alkyne, Alkene, Hydrocarbon, Aldehyde, Bond length

27

4,4'-Bis-(4-pentenyl)-dithieno[3,2-b:2',3'-d]germole was synthesized as a functional building block for the efficient preparation of dithienogermole (DTG) derivatives with varying alkyl chain lengths and pendant functionalities in excellent yields. These derivatives were efficiently isolated via olefin cross-metathesis followed by hydrogenation.

Concepts: Alkyne, Chemical synthesis, Alkene, Functional groups, Alkane, Synthesis, Aldehyde, Alkyl

27

A ‘Cu'te couple: A synthetically useful protocol for the preparation of N-alkynylated sulfoximines (yne sulfoximines) has been developed. The method involves a mild copper-catalyzed oxidative cross-coupling of NH-sulfoximines and terminal alkynes. The corresponding N-acyl sulfoximines were also obtained selectively after acid-catalyzed hydrolysis of the yne sulfoximines.

Concepts: Method acting, Hydrogenation, Alkyne, Alkene, Sonogashira coupling

26

A highly efficient molecular iodine mediated formal [3 + 2 + 1] cycloaddition reaction for the direct synthesis of substituted quinolines from methyl ketones, arylamines, and styrenes is developed. The methyl group of the methyl ketone represents uniquely reactive input in the Povarov reaction. A self-sequenced iodination/Kornblum oxidation/Povarov/aromatization mechanism has been proposed as a possible reaction sequence to account for the results observed in this study.

Concepts: Oxygen, Alkyne, Ketone, Functional groups, Imine, Quinoline, Povarov reaction, Cycloadditions

25

Carbonylation. A palladium-catalyzed carbonylative Sonogashira coupling with formic acid as the CO source has been developed by Xiao-Feng Wu et al. in their Communication on page 1870, which is featured on the Inside Cover. Using aryl iodides and terminal alkynes as the substrates, and acid anhydride as the additive, the corresponding alkynones were isolated in moderate-to-good yields. Good functional group tolerance can be observed as well. Compared with the known procedures, one of the most obvious advantages of this method is easy operation.

Concepts: Oxygen, Chemical reaction, Alkyne, Alkene, Acetic acid, Functional groups, Carboxylic acid, Sonogashira coupling