Olefin also coupling

Catalytic reactions at somewhat lower temperatures also produce ethylene and other olefins. When coupled with a methane process to methyl chloride, this reaction results ia a new route to the light hydrocarbons that is of considerable interest. 

The pyrolysis of perfluoro carboxylic salts can result both in mono and bimolecular products At 210-220 °C, silver salts give mostly the coupled products, at 160-165 °C in A -methylpyrrolidinone, the corresponding copper salts also give the simple decarboxylated compounds in nearly equal amounts The decomposition of the copper salts m the presence of lodobenzene at 105-125 °C results m a phenyl derivative, in addition to the olefin and coupled product [94] (equations 60-62)... 

When furan or substituted furans were subjected to the classic oxidative coupling conditions [Pd(OAc)2 in refluxing HOAc], 2,2 -bifuran was the major product, whereas 2,3 -bifuran was a minor product [12,13]. Similar results were observed for the arylation of furans using Pd(OAc)2 [14]. The oxidative couplings of furan or benzo[i]furan with olefins also suffered from inefficiency [15]. These reactions consume at least one equivalent of palladium acetate, and therefore have limited synthetic utility. 

The direct oxidative carboxylation of olefins has great potential, and many advantages. Notably, it does not require the C02 to be free of dioxygen this is an especially attractive feature, as the cost to purify C02 is extremely high, and may discourage its use. Moreover, the direct oxidative carboxylation of olefins can couple two processes-the epoxidation of olefins, and the carbonation of epoxides. Hence, the process makes direct use of those olefins that are available commercially at low price, and which represent an abundant feedstock. Such an approach also avoids having to isolate the epoxide. 

For the Heck reaction as discussed in Section III.2.1 the final position of the olefi-nic double bond of the products must not necessarily be the same as in the starting materials (for example Schemes 8, 9, and 10 of Section III.2.1) [1], The selectivity is often driven by stereochemical requirements, because the /1-hydrogen elimination step which forms the double bond proceeds exclusively in a syn manner (if a trans /3-hydrogen is eliminated, one should suspect major deviations from the general mechanism of the Heck reaction, for example electrophilic substitution instead of carbopalladation). An impressive example of a double bond migration is depicted in Scheme 1 - instead of olefins the coupling reaction of iodobenzene 1 with the olefmic alcohol 2 results in the isomeric aldehydes 3 and 4 as final products [2], Reactions of this type have emerged as valuable tools for the synthesis of carbonyl compounds and also as crucial steps in domino processes. 

The carbinyl carbon is a methylene group (from the 13C/DEPT) and it is a doublet (with some long-range coupling from H-10) at 84.15 in the H NMR spectrum. Since the only methine groups in the structure are olefinic (also from the 13C/DEPT), the compound must... 

Foimalion ol olefins by coupling or cross coupling of ketones, mediated by low valent Manium Also coupling ol enol ethers ol 1,3-dicarbonyl compounds. 

A small amount of bisthiophene was isolated when thiophene was treated with Pd(OAc), [35]. The oxidative couplings of a thiophene with thiophene, furan, or substituted arenes were achieved in poor to moderate yields using PdfOAc), in HOAc [36-38]. The oxidative couplings of thiophene or benzo[Z ]thiophene with olefins also suffer from inefficiency [39]. 

Reductive coupling of carbonyl compounds to olefins. Reductive coupling of carbonyls to olefins with a low-valent titanium reagent prepared from TiCla and LiAlHi (6, 589) tends to give erratic yields. McMurry and Fleming find that use of Ti(0) gives reproducible results. Yields are somewhat higher with metal prepared with potassium, but lithium is easier to handle. 1,2-Diols are also reduced to olefins. ... 

Mizoroki-Heck couplings of bromo- and chloroarenes were successfully achieved by using the electron-rich benzimidazolylidene palladium complex 2 (Figure 15.1), generated in situ in tetrabutylammonium bromide as solvent [29]. The coupling of 4-chloroacetophenone with butyl acrylate in the presence of 1 mol% 2 yields 93% 4-acetyl-(El-cinnamic ester in 6 h reaction time. Butyl acrylate was also coupled with 2 equiv of bromobenzene leading to the trisubstituted olefin 3,3-diphenylpropenoic acid butyl ester in 91% yield. 

The radical species RR C(0)Sml2, resulting from the reaction between an aldehyde or a ketone and Sml2, can also couple with another carbonyl (to give c/s-diols), an olefin or an alkyne leading to the formation of a C-C bond. Such an example is provided by a key step of the synthesis of isocarbacycline ... 

The considerations discussed in detail in connection with the chemical, configurational, and conformational structure of polypropylene apply similarly to poly-1-butene and the higher poly-1-olefins. Also with poly-1-butene, the preferred backbone conformation is tgtg for the isotactic chain [37]. The various crystalline modifications correspond to greater or lesser deviations from these ideal chain conformations, coupled with variations in chain packing in the crystal lattice. 

The Fischer-Tropsch reaction is essentially that of Eq. XVIII-54 and is of great importance partly by itself and also as part of a coupled set of processes whereby steam or oxygen plus coal or coke is transformed into methane, olefins, alcohols, and gasolines. The first step is to produce a mixture of CO and H2 (called water-gas or synthesis gas ) by the high-temperature treatment of coal or coke with steam. The water-gas shift reaction CO + H2O = CO2 + H2 is then used to adjust the CO/H2 ratio for the feed to the Fischer-Tropsch or synthesis reactor. This last process was disclosed in 1913 and was extensively developed around 1925 by Fischer and Tropsch [268]. 

Other approaches to direct C2Q couplings have been reported (9,30—35). Based on their knowledge of sulfone chemistry, Rhc ne-Poulenc has patented many syntheses of P-carotene which use this olefination chemistry (36—41). Homer-Emmons chemistry has also been employed for this purpose (42). The synthetic approaches to the carotenoids have been reviewed (43). 

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