Acetylides are reagents in organic synthesis
amounts that are significant when considering use of the reaction in synthesis
Examples of how to use the word acetylene in a sentence
The hydrogen atoms in acetylene can be replaced by metallic elements to form acetylides--e.g., acetylides of silver, copper, or sodium. The acetylides of silver, copper, mercury, and gold are
detonated by heat, friction, or shock. In addition to its reactive hydrogen atom, the carbon-carbon triple bond can readily add halogens, halogen acids, hydrogen cyanide, alcohols, amines,
and amides. Acetylene can also add to itself or to aldehydes and ketones. Many of the reactions mentioned here are used for the commercial manufacture of various industrial and consumer
products, such as acetaldehyde, the synthetic rubber neoprene, water-base paints, vinyl fabric and floor coverings, dry-cleaning solvents, and aerosol insecticide sprays. Acetylene is
produced by any of three methods: by reaction of water with calcium carbide, by passage of a hydrocarbon through an electric arc, or by partial combustion of methane with air or oxygen.
Structurally, colchicine (1) possesses an unusual 6–7–7 tricyclic ring system, and NCME (2) possesses a 6–7–6 carbocyclic skeleton. The stereocenter at C-7 and the a-configured chiral axis defined by the pivot bond joining the A and C rings, and the regioselective construction of the highly oxidized tropolone C-ring, represent formidable synthetic challenges. It is noteworthy that another colchicinoid β-lumicolchicine (3) has a novel tetracyclic 6–7–4–5 membered ring system with three stereocenters, and α-lumicolchicine (4) has a unique nonacyclic 6–7–4–5–4–5–4–7–6 ring skeleton with ten stereocenters.
Pyridine synthesis - Organic chemistry
A concise and highly enantioselective synthesis of colchicine (>99% ) in eight steps and 9.3% overall yield, without the need for protecting groups, was developed. A unique Wacker oxidation was used for enabling regioselective construction of the highly oxidized and synthetic challenging tropolone C-ring. Furthermore, asymmetric syntheses of β-lumicolchicine and -acetylcolchinol--methyl ether (NCME) were achieved. Notably, NCME was synthesized from β-lumicolchicine by an unusual decarbonylation and electrocyclic ring-opening cascade reaction.
Owing to their unusual structural motifs and promising pharmacological properties, colchicine (1) and NCME (2) have attracted considerable attention from synthetic chemists, which has resulted in several elegant total syntheses of 1 and 2. Recently, we developed an enantioselective synthesis of colchicine (1) from commercially available and inexpensive 2,3,4-trimethoxybenzaldehyde (5). The challenging tricyclic 6–7–7 core of colchicinoids was efficiently introduced using an intramolecular oxidopyrylium-mediated [5 + 2] cycloaddition reaction. In our continuing efforts toward the synthesis of biologically active natural products, we herein describe a modified concise and highly enantioselective synthesis of colchicine using the Wacker oxidation for the regioselective construction of the highly oxidized tropolone C-ring. Moreover, asymmetric total syntheses of β-lumicolchicine and NCME were also achieved.
Use of the word acetylene in a sentence example
Since Germany was cut off from
key raw materials such as natural rubber during World War II, butanediol was used to produce the synthetic rubber Buna.
The bombing of Ludwigshafen forced Reppe to transfer in September 1944 to the inorganic facility at Gendorf in Upper Bavaria, where he conducted olefin
high pressure experiments in a smaller laboratory.
Retrosynthetically (), β-lumicolchicine (3) could be prepared from colchicine (1) through a 4π-electrocyclization reaction. We anticipate that NCME (2) would be synthesized from 3 through a Rh-catalyzed decarbonylation process via intermediate A to give the fused bicyclobutene B, followed by an electrocyclic ring-opening reaction. The formation of the more stable aromatic ring C is one of the driving forces for this process. It was envisioned that colchicine (1) could be generated from 6 through a Wacker oxidation, followed by the regioselective formation of the tropolone C-ring. Tricyclic 6 could itself be synthesized from 7 through the intramolecular oxidopyrylium-mediated [5 + 2] cycloaddition reaction. Compound 7 could be synthesized from 5 through several simple functional group transformations reported previously.
large volume of their use in petrochemical synthesis.
It is a hydrocarbon and the simplest alkyne
Acetylene, HC≡CH, is one of the primary building blocks in synthetic organic and industrial chemistry
Acetylene Chemistry: Chemistry, Biology and ..
Handbook of Reagents for Organic Synthesis, Reagents for Silicon-Mediated ..
class of compounds in organic synthesis
Alkynation is an addition reaction in organic synthesis where a metal acetylide ..
involving the Use of Zn(ii) Salts 114
Dilution of acetylene with inert nitrogen gas and the use of stainless
steel, walled reactor tubes were key discoveries in working safely with acetylene at pressures up to 200 atm.
Reppe now began to synthesize a wide variety of different vinyl compounds.
Acetylene: Production and Use - Chemgapedia
To make a resin of the Bakelite,
phenol is reacted with acetylene at a pressure of 10 atm.
Organic zinc salts, for example the naphthenate, are good catalysts for the phenol-acetylene reaction and they can give substituted oxy-styrenes that are
Although the mercaptans, as mentioned above, react with acetylene to give products analogous to those derived from the oxygen alcohols, the products
are malodorous and are not of particularly practical value.
Korosin, the adhesive for synthetic rubber, is made by reacting isobutylphenol with acetylene.
remote locations to the synthesis of a host of organic ..
In summary, we developed a concise and highly enantioselective synthesis of colchicine (>99% ) in eight steps in 9.3% overall yield without the need for protecting groups. An unusual Wacker oxidation was used for enabling the regioselective construction of the highly oxidized tropolone C-ring. β-Lumicolchicine was prepared through a 4π-electrocyclization reaction with a much-improved yield compared with existing procedures, and the allocolchicinoid NCME was synthesized from β-lumicolchicine through a novel decarbonylation/electrocyclic ring-opening cascade reaction.
Synthesis - Home - Michigan State University
Most countries at that time prohibited such experiments and in
Germany, the Acetylene Ordinance only allowed handling acetylene below 1.5 atm.
But Reppe wanted to use the gas to produce small organic molecules, monomers, for experiments in the newly emerging field of plastics.
The study of organic chemistry exposes a ..
During the Third Reich, most chemists adopted Hitler’s anti-Semitic policies without contest, and many actively participated in research programs that advanced Hitler’s goals. Yet one certain act of defiance against the regime was Max Planck’s attempt to organize a memorial for Haber in 1935, a reflection of the esteem in which Haber was held by his colleagues, some of whom attended at great personal risk.
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