Catalytic reaction with acetylene

At the end of the 1920 s, Walter Reppe (29, 30, 31, 32) started his experiments on catalytic reactions with acetylene under pressure. On the basis of his studies, which soon were known all over the world as Reppe chemistry, it was possible to construct complicated organic compounds of high value from simple building stones. From the standpoint of the chemical engineer the greatness of his achievement was that the... 

In general, the acetylenic triple bond is highly reactive toward hydrogenation, hydroboration, and hydration in the presence of acid catalyst. Protection of a triple bond in disubstituted acetylenic compounds is possible by complex formation with octacarbonyl dicobalt [Co2(CO)g Eq. (64) 163]. The cobalt complex that forms at ordinary temperatures is stable to reduction reactions (diborane, diimides, Grignards) and to high-temperature catalytic reactions with carbon dioxide. Regeneration of the triple bond is accomplished with ferric nitrate [164], ammonium ceric nitrate [165] or trimethylamine oxide [166]. 

In continuation of Reppe chemistry, catalytic reactions of acetylene with carbon monoxide and compounds containing hydrogen atoms, e.g. water or alcohol, were developed in the process of carbonylation (31), as seen in Equations 3 and 4. 

The palladium-catalyzed domino assembly of norbornene (65), the ds-alkenyl iodide 66, and a terminal alkyne or cyanide reported by Torii, Okumoto et al. [315] provides an example for a sequence of oxidative addition, intermolecular double bond insertion, and interception of a copper acetylide or potassium cyanide. These reactions with acetylenes have been performed in good yields in the presence of diethylamine, tetra-n-butylammonium chloride, and catalytic amounts of palladium acetate, triphenylphosphine, and copper] I) iodide. Remarkably, they are characterized by complete inversion of the cis configuration of the alkenyl iodide and a high degree of discrimination for the enantiotopic ends of the double bond in norbornene. To account for that, intermediate formation of a cyclopropylcarbinyl-palladium species by a 3-exo-trig cyclization in 67 and subsequent cycloreversion to a new homoallylpalladium intermediate as the direct precursor to 68 and 69 has been assumed. Thus, the products 68 and 69 are formed virtually with complete stereoselectivity (Scheme 8.17). 

In the first method a secondary acetylenic bromide is warmed in THF with an equivalent amount of copper(I) cyanide. We found that a small amount of anhydrous lithium bromide is necessary to effect solubilization of the copper cyanide. Primary acetylenic bromides, RCECCH Br, under these conditions afford mainly the acetylenic nitriles, RCsCCHjCsN (see Chapter VIII). The aqueous procedure for the allenic nitriles is more attractive, in our opinion, because only a catalytic amount of copper cyanide is required the reaction of the acetylenic bromide with the KClV.CuCN complex is faster than the reaction with KCN. Excellent yields of allenic nitriles can be obtained if the potassium cyanide is added at a moderate rate during the reaction. Excess of KCN has to be avoided, as it causes resinifi-cation of the allenic nitrile. In the case of propargyl bromide 1,1-substitution may also occur, but the propargyl cyanide immediately isomerizes under the influence of the potassium cyanide. 

The stoichiometric and the catalytic reactions occur simultaneously, but the catalytic reaction predominates. The process is started with stoichiometric amounts, but afterward, carbon monoxide, acetylene, and excess alcohol give most of the acrylate ester by the catalytic reaction. The nickel chloride is recovered and recycled to the nickel carbonyl synthesis step. The main by-product is ethyl propionate, which is difficult to separate from ethyl acrylate. However, by proper control of the feeds and reaction conditions, it is possible to keep the ethyl propionate content below 1%. Even so, this is significantly higher than the propionate content of the esters from the propylene oxidation route. 

The reactivity of arylhalides in the acetylenic condensation sharply decreases in the series Ar—I, Ar—Br, Ar—Cl. The rate of reaction of phenylacetylene with iodo derivatives is 800 times higher than that of the reaction with bromo derivatives and is 10 higher than that of the reaction with corresponding chlorides (75JOM253). Taking into account the very low activity of halogenopyrazoles (66AHC347), the catalytic variant of acetylenic condensation mainly involves the most active iodo derivatives. 

Yamamoto et al. have developed a catalytic enantioselective carbo-Diels-Alder reaction of acetylenic aldehydes 7 with dienes catalyzed by chiral boron complexes (Fig. 8.10) [23]. This carbo-Diels-Alder reaction proceeds with up to 95% ee and high yield of 8 using the BLA catalyst. The reaction was also investigated from a theoretical point of view using ab-initio calculations at a RHF/6-31G basis set. 

Fig. 8.10 The catalytic enantioselective carbo-Diels-Alder reaction of acetylenic aldehydes 7 with cyclopentadiene 2 catalyzed by chiral...

Vinyl acetate was originally produced hy the reaction of acetylene and acetic acid in the presence of mercury(II) acetate. Currently, it is produced hy the catalytic oxidation of ethylene with oxygen, with acetic acid as a reactant and palladium as the catalyst ... 

The pincer-type palladacycle (120) (R = 1Pr), which is actually a derivative of a dialkylphos-phinous acid (themselves excellent ligands see Section 9.6.3.4.6) was shown to allow the crosscoupling of aryl chlorides with terminal acetylenes ((120), ZnCl2, Cs2C03, dioxane, 160 °C). However the high reaction temperature may be prohibitive for the actual application of this catalytic system, as acetylenes are known to be thermally sensitive.433 The same palladacycle (R = Ph) is effective in the Suzuki-Miyaura reaction with aryl bromides and activated aryl chlorides (K2C03, toluene, 130 °C). 

Transition metal-mediated C-C bond formation through reaction of C02 with acetylenes and dienes can serve as a useful method for the construction of various carbon skeletons, such as linear and cyclic carboxylic acids, and esters and lactams. Enantioselective incorporation of C02 can also be achieved, especially when combined with sterically controlled formation of cyclic carbo- or heterocyclic skeletons. In perspective of the future in this area, development of more efficient and more selective catalytic systems for incorporation or transformation of C02 into useful fine chemicals and polymer materials will continue to be an important and attractive research target. 

The original route to acrylonitrile was the catalytic reaction of HCN with acetylene. That was a combination of two compounds that together had all the characteristics youd like to avoid—poisonous, explosive, corrosive, and on and on. But during World War II, acrylonitrile became very important as a comonomer for synthetic rubber (nitrile rubber). Later, the growth for acrylonitrile came from synthetic fibers like Orion, Acrylon, and Dynel. 

In the 1960s, like almost all acetylene technology, the HCN/C2H2 route to acrylonitrile gave way to ammoxidation of, propylene. Thar word, ammoxidation, looks suspiciously like the contraction of two more familiar terms, ammonia and oxidation, and it is. When Standard of Ohio (Sohio) was still a company they developed a one-step vapor phase catalytic reaction of propylene with ammonia and air to give acrylonitrile. 

By the example of 34 different alkynes, it was convincingly demonstrated that the product of the treatment of [PtCLJ with CO at 40-110 °C is a very powerful alkyne hydration catalyst some of the reactions are shown on Scheme 9.7 [25], The best medium for this transformation is THF containing 5 % H2O. The reaction can also be performed in a water-organic solvent two-phase system (e.g. with 1,2-dichloroethane), however in this case addition of a tetralkylammonium salt, such as Aliquat 336, is required to facilitate mass transfer between the phases. After the reaction with CO, the major part of platinum is present as H2[ Pt3(CO)6 n], but the catalytic effect was assigned to a putative mononuclear Pt-hydride, [PtHCl(CO)2], presumably formed from the cluster and some HCl (supplied by the reduction of [PtCU]). The hydration of terminal acetylenes follows Markovnikov s mle leading exclusively to aldehyde-free ketones. 

The first anti-Markovnikov hydration of terminal acetylenes, catalyzed by mthenium(ll)-phosphine complexes, has been described in 1998 [27]. As shown on Scheme 9.8, the major products were aldehydes, accompanied by some ketone and alcohol. In addition to TPPTS, the fluorinated phosphine, PPh2(C6Fs) also formed catalytically active Ru-complexes in reaction with [ RUC12(C6H6) 2]. 

The catalytic reaction may also be carried out with two different al-kynes. For example, the cocyclization of acetylene and propyne with acetonitrle yields a mixture of dimethylpyridine (lutidines) in addition to 2-methylpyridine and the isomeric collidines. The cocyclization [Eq.(23)] is not selective and appears to occur statistically. 

Before a batch of CaHj is used, a small sample should be mixed with a few drops of water and the evolved gases smelt cautiously (or analysed by GLC). If the nose can sense phosphine or the GLC shows up acetylene, the batch should be returned to the manufacturer. Although in theory both gases would be pumped off during the reevacuation of the liquid compound to remove the hydrogen, enough might remain to interfere with catalytic reactions. 

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