Synthesis from acetylene

Bis-acetylene synthesis from alkynyl halides and alkynyl copper reagents. Cf. Castro-Stephens reaction. 

Historically, the use of acetylene as raw material for chemical synthesis has depended strongly upon the avadabihty of alternative raw materials. The United States, which until recendy appeared to have limitless stocks of hydrocarbon feeds, has never depended upon acetylene to the same extent as Germany, which had more limited access to hydrocarbons (1). During Wodd War 1 the first manufacture of a synthetic mbber was undertaken ia Germany to replace imported natural mbber, which was no longer accessible. Acetylene derived from calcium carbide was used for preparation of... 

Hydrogenation of Acetylenes. Complete hydrogenation of acetylenes to the corresponding alkanes, which maybe requited to remove acetylenic species from a mixture, or as a part of a multistep synthesis, may be accompHshed using <5 wt % palladium or platinum on alumina in a nonreactive solvent under very mild conditions, ie, <100°C, <1 MPa (10 atm). Platinum is preferred in those cases where it is desired to avoid isomeri2ation of the intermediate olefin. Silver on alumina also can be used in this appHcation as can unsupported platinum metal. 

FRITSCH BUTTENBERG - WIECHELL Acetylene Synthesis Alpha elimination from haloethylenes leading via carbene rearrangement to acetylenes... 

KHAND PAUSON Cyclopentenone Annulat/on Cyclopentenone synthesis from cartxin monoxide acetylene and olefins, cobalt carbonyl catalyzed. 

STEPHENS CASTRO Acetylene cycloptiane synthesis Polyacetylene cyclophane synthesis from an iodophenyl copper acetylide... 

Direct substitution of the carbonyls themselves is of course possible. Besides Group 15 donor ligands, unsaturated hydrocarbons give especially interesting products. The iron carbonyl acetylenes provided early examples of the use of carbonyls in organic synthesis. From them a wide variety... 

Internationally renowned authors, among them K. C. Nicolaou, H. Iwamura, R. H. Grubbs and H. Hopf, present the full potential of acetylene chemistry, from organic synthesis through materials science to bioorganic chemistry. 

The fruit of a shrub that grows in Sierra Leone is very toxic and has been used as a rat poison. The toxic principal has been identified as Z-18-fluoro-9-octadecenoic acid. Suggest a synthesis from 8-fluorooctanol, l-chloro-7-iodoheptane, acetylene, and any other necessary organic or inorganic reagents. 

The well documented synthetic method for 37 is chlorination of cyclopropyl-methylketone followed by base treatment [29]. However, this method did not provide a suitable impurity profile. The most convenient and suitable method we found was the one-step synthesis from 5-chloro-l-pentyne (49) by addition of 2equiv of base, as shown in Scheme 1.18 [21, 30]. Two major impurities, starting material 49 and reduced pentyne, had to be controlled below 0.2% each in the final bulk of 37, to ensure the final purity of Efavirenz . Acetylene 37 was isolated by distillation after standard work-up procedure. 

Very many naturally occurring 3-alkyl- or 3-acylfurans are now routinely synthesized by preparing a substrate for treatment with 3-furyllithium, itself made from 3-bromofuran according to Fukuyama, Tokoroyama, and Kubota, who used it to obtain pyroangensolide and fraxinellone.212 Equally, 2-lithiofuran is used for such natural products as the acetylenic furans from Alphonsea ventricosa213 and other compounds.214 For the synthesis of the sesquiterpenoid sponge-metabolite pleraplysillin-2 78, the lithiofuran 79 and therefore the bromofuran 80 was needed to secure the orientation a suitable preparation was devised for 80.215... 

The scope of the Patemo-Buchi cycloaddition has been widely expanded for the oxetane synthesis from enone and quinone acceptors with a variety of olefins, stilbenes, acetylenes, etc. For example, an intense dark-red solution is obtained from an equimolar solution of tetrachlorobenzoquinone (CA) and stilbene owing to the spontaneous formation of 1 1 electron donor/acceptor complexes.55 A selective photoirradiation of either the charge-transfer absorption band of the [D, A] complex or the specific irradiation of the carbonyl acceptor (i.e., CA) leads to the formation of the same oxetane regioisomers in identical molar ratios56 (equation 27). 

The preparation of acetylenic ketones from soluble silver acetylenides and acid chlorides was reported in 1956 (Scheme 108).512 Analogously to that report, the reaction of silver acetylenides with acylpyridinium salts was reported to proceed effectively.513 This chemistry was applied to the synthesis of cotarnine derivatives, as exemplified in Scheme lQ9.514 514a... 

Linalool is an important fragrance and fragrance precursor (esters) with an annual production of over 15 000 t. Some 50% is made by semi-synthesis from a- and / -pinene, the other part is made synthetically starting from isobutene via 6-methylhept-5-en-2-one (9). Addition of an acetylene fragment followed by partial hydrogenation (Pd) leads to linalool. 

In the 1930s it was discovered that the pyrolysis of alkanes produced large quantities of olefins. This pyrolysis process is not very selective, but the costs of separation were cheaper, and scaleup was simpler and safer in making ethylene rather than acetylene so during the 1940s ethylene and other small olefins replaced acetylene as the major building block in chemical synthesis. We will consider the reactions and reactors used in olefin synthesis from alkanes in the next chapter. 

The steam-volatility of isomeric thienothiophenes allows separation from the resinous products formed during their synthesis from citric acid or acetylene. Selenophenoselenophenes are also steam-volatile. It is, however, very difficult to separate the isomeric thienothiophenes from each other and from benzo[b]thiophene with which they are also... 

Highly enantioenriched 4-alken-l-yn-3-ol moieties present in many bioactive acetylenic metabolites from sponges have been efficiently obtained by reduction of the parent 1-trimethylsilyI-4-alken-l-yn-3-one 18 with Alpine-borane or with BH3-SMe2 in the presence of chiral oxazaborolidines, followed by desilylation of the resulting alcohol. This strategy has been applied to the first stereoselective synthesis of petrofuran 19 <99SL429>. 

Synthesis from Dehydrolinalool. Dehydrolinalool is produced on a large scale from 6-methyl-5-hepten-2-one and acetylene and can be isomerized to citral in high yield by a number of catalysts. Preferred catalysts include organic orthovanadates [55], organic trisilyl oxyvanadates [56], and vanadium catalysts with silanols added to the reaction system [57]. 

Methane is an important starting material for numerous other chemicals. The most important of these are ammonia, methanol, acetylene, synthesis gas, formaldehyde, chlorinated methanes, and chlorofluorocarbons. Methane is used in the petrochemical industry to produce synthesis gas or syn gas, which is then used as a feedstock in other reactions. Synthesis gas is a mixture of hydrogen and carbon monoxide. It is produced through steam-methane reforming by reacting methane with steam at approximately 900°C in the presence of a metal catalyst CH4 + H20 —> CO + 3H2. Alternately, methane is partially oxidized and the energy from its partial combustion is used to produce syn gas ... 

Selective synthesis of acetylene (>90%) from methane was accomplished by microwave plasma reactions.568 Conversion of methane to acetylene by using direct current pulse discharge was performed under conditions of ambient temperature and atmospheric pressure.569 The selectivity of acetylene was >95% at methane conversion levels ranging from 16 to 52%. In this case oxygen was used to effectively remove deposited carbon and stabilize the state of discharge. Similar high... 

Wide practical application of erythritol tetranitrate has been prevented by the lack of readily available raw material. The main sources of erythritol are certain kinds of moss and sea-weeds, though chemical synthesis from acetylene, according to the following scheme, has been suggested by Reppe [2] ... 

In attempts (76IZV690 80KGS1299 81MI4) to extend the pyrrole synthesis from ketoximes and acetylenes to aldoximes, the oximes of both aliphatic and aromatic aldehydes have been found to readily convert to the corresponding nitriles upon moderate heating (60-140°C) in KOH/DMSO. 

Having established that the end game of the proposed synthesis of cylindrospermopsin (1) from bromoketone 4 was viable, we turned our attention to the preparation of acetylene 5 from 4-methoxy-3-methylpyridine (7). 4-Methoxy-3-methylpyridine (7) was prepared by modifications of the literature procedure.17,18 3-Methyl-4-nitropyridine A-oxide (27),19 was treated with K2CO3 in methanol at 70 °C to displace the nitro group to... 

In light of the mass spectrometric results described above, a rational fullerene synthesis from cyclophyne precursors appears to be within reach. Since superphane 21 [43] and superferrocenophane 22 [44] are established structural precedences, it may well be that reports about a successful synthesis of superphyne 23, an acetylenic isomer of buckmin-sterfullerene, or even a corresponding supermetallophyne are only a short time away. 

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