Direct Synthesis of Symmetric Diarylethynes from Calcium Carbide and Arylboronic Acids/Esters

1,2,4-Triazines and Calcium Carbide in the Catalyst-Free Synthesis of 2,3,6-Trisubstituted Pyridines and Their D-, 13 C-, and Doubly D2 -13 C2 -Labeled Analogues

A novel synthetic approach to 2,3,6-trisubstituted pyridines, their 4,5-dideuterated derivatives, 4,5-13 C2 - and doubly-labeled D2 -13 C2 -pyridines has been developed using catalyst-free [4+2] cycloaddition of 1,2,4-triazines and in situ generated acetylene or labeled acetylene. Calcium carbide and water or deuterium oxide were used for the in situ generation of acetylene and dideuteroacetylene. Calcium carbide-13 C2 in the mixture with water or deuterium oxide was applied as 13 C2 -acetylene and D2 -13 C2 -acetylene source.

Selective Monoethynylation of 2-Oxoacetamides Using Calcium Carbide as a Concise Solid Alkyne Source

An efficient selective monoethynylation of 2-oxoacetamides using calcium carbide as a concise solid alkyne source is described. A series of multifunctional compounds, 2-hydroxybut-3-ynamides, are synthesized by this strategy. The salient features of this protocol are the use of inexpensive and easy-to-handle solid alkyne source as a surrogate of inflammable and explosive gaseous acetylene, transition-metal-free and mild condition, wide scope of substrates, high selectivity, high yield, and simple work-up procedure.

Copper-Catalyzed Construction of Benzo[4,5]imidazo[2,1-a]isoquinolines Using Calcium Carbide as a Solid Alkyne Source

A method for the synthesis of benzo[4,5]imidazo[2,1-a]isoquinolines through Sonogashira cross-coupling/nucleophilic addition tandem reactions using calcium carbide as a solid alkyne source, 2-(2-bromophenyl)benzimidazoles as starting materials, and copper as a catalyst is described. The target products can also be synthesized through one-pot three-component reactions of o-phenylenediamines, o-bromobenzaldehydes, and calcium carbide. Both reaction routes can also be scaled up to gram scale.

3D Printing to Increase the Flexibility of the Chemical Synthesis of Biologically Active Molecules: Design of On-Demand Gas Generation Reactors

The development of new drugs is accelerated by rapid access to functionalized and D-labeled molecules with improved activity and pharmacokinetic profiles. Diverse synthetic procedures often involve the usage of gaseous reagents, which can be a difficult task due to the requirement of a dedicated laboratory setup. Here, we developed a special reactor for the on-demand production of gases actively utilized in organic synthesis (C2H2, H2, C2D2, D2, and CO2) that completely eliminates the need for high-pressure equipment and allows for integrating gas generation into advanced laboratory practice. The reactor was developed by computer-aided design and manufactured using a conventional 3D printer with polypropylene and nylon filled with carbon fibers as materials. The implementation of the reactor was demonstrated in representative reactions with acetylene, such as atom-economic nucleophilic addition (conversions of 19-99%) and nickel-catalyzed S-functionalization (yields 74-99%). One of the most important advantages of the reactor is the ability to generate deuterated acetylene (C2D2) and deuterium gas (D2), which was used for highly significant, atom-economic and cost-efficient deuterium labeling of S,O-vinyl derivatives (yield 68-94%). Successful examples of their use in organic synthesis are provided to synthesize building blocks of heteroatom-functionalized and D-labeled biologically active organic molecules.

Direct Synthesis of 3-Coumaranones with Calcium Carbide as an Acetylene Source

A novel synthesis method for the construction of 3-coumaranones from the reaction of two molecules, calcium carbide and salicylaldehyde, was reported. Various 2-methyl-2-vinylbenzofuran-3(2H)-ones could be obtained in moderate yields in the absence of a metal catalyst. The salient features of this protocol involve widely available starting materials, an inexpensive and easy-to-handle alkyne source, and a cost-efficient route. The reaction mechanism was verified by density functional theory calculations of possible intermediates and corresponding transition states.

Synthesis of Diarylethynes from Aryldiazonium Salts by Using Calcium Carbide as an Alkyne Source in a Deep Eutectic Solvent

An efficient method for the synthesis of diarylethynes from aryldiazonium salts by using calcium carbide as an alkyne source at room temperature in a deep eutectic solvent is described. The salient features of this protocol are an inexpensive and easy-to-handle alkyne source, a nonvolatile and recyclable solvent, mild conditions, and a simple workup procedure.

Synthesis of aromatic terminal allenes and aliphatic terminal alkynes from hydrazones using calcium carbide as an acetylene source

A simple method for the selective synthesis of aromatic terminal allenes and aliphatic terminal alkynes from the reactions of calcium carbide with ketone and aldehyde p-tosylhydrazones using copper as a mediator is described.

Efficient labeling of organic molecules using 13C elemental carbon: universal access to 13C2-labeled synthetic building blocks, polymers and pharmaceuticals

Synthetic methodology enabled by ¹³C-elemental carbon is reported. Calcium carbide Ca¹³C₂ was applied to introduce a universal ¹³C₂ unit in the synthesis of labeled alkynes, O,S,N-vinyl derivatives, labeled polymers and ¹³C₂-pyridazine drug core.

Pd/MCM-41 catalyst for acetylene hydrogenation to ethylene

This study aims to produce ethylene using the calcium carbide route, acetylene from calcium carbide and then selective hydrogenation of the high-concentration acetylene to ethylene. A series of catalysts with different supports, such as Al2O3, SiO2 and MCM-41, were prepared using the ethylene glycol reduction method and their catalytic properties for high-concentration acetylene hydrogenation of calcium carbide to ethylene were studied by transmission electron microscopy, X-ray powder diffraction and thermogravimetry, among others. The results show that the small particle size and uniform dispersion of palladium (Pd) particles in the Pd/MCM-41 catalyst produced the highest ethylene yield of 62.09%. Then, the conditions for the basic reaction, such as reaction temperature and space velocity, were optimized using MCM-41 as a support. The yield of ethylene after condition optimization was as high as 82.87%, while the loading of Pd was 0.1%.

Calcium-Based Sustainable Chemical Technologies for Total Carbon Recycling

Calcium carbide, a stable solid compound composed of two atoms of carbon and one of calcium, has proven its effectiveness in chemical synthesis, due to the safety and convenience of handling the C≡C acetylenic units. The areas of CaC₂ application are very diverse, and the development of calcium-mediated approaches resolves several important challenges. This Review aims to discuss the laboratory chemistry of calcium carbide, and to go beyond its frontiers to organic synthesis, life sciences, materials and construction, carbon dioxide capturing, alloy manufacturing, and agriculture. The recyclability of calcium carbide and the availability of large-scale industrial production facilities, as well as the future possibility of fossil-resource-independent manufacturing, position this compound as a key chemical platform for sustainable development. Easy regeneration and reuse of the carbide highlight calcium-based sustainable chemical technologies as promising instruments for total carbon recycling.

Acetylene in Organic Synthesis: Recent Progress and New Uses

Recent progress in the leading synthetic applications of acetylene is discussed from the prospect of rapid development and novel opportunities. A diversity of reactions involving the acetylene molecule to carry out vinylation processes, cross-coupling reactions, synthesis of substituted alkynes, preparation of heterocycles and the construction of a number of functionalized molecules with different levels of molecular complexity were recently studied. Of particular importance is the utilization of acetylene in the synthesis of pharmaceutical substances and drugs. The increasing interest in acetylene and its involvement in organic transformations highlights a fascinating renaissance of this simplest alkyne molecule.

Direct Synthesis of 2-Methylbenzofurans from Calcium Carbide and Salicylaldehyde p-Tosylhydrazones

A new methodology for the construction of methyl-substituted benzofuran rings from the reactions of calcium carbide with salicylaldehyde p-tosylhydrazones/2-hydroxyacetophenone p-tosylhydrazones is described. Various 2-methylbenzofurans and 2,3-dimethylbenzofurans could be obtained in satisfactory yield by using a cuprous chloride catalyst. The advantages of this protocol include the use of a readily available and easy-to-handle acetylene source and simple workup procedure.