2,7-Octadiene

An active catalytic species in the dimerization reaction is Pd(0) complex, which forms the bis-7r-allylpalladium complex 3, The formation of 1,3,7-octa-triene (7) is understood by the elimination of/5-hydrogen from the intermediate complex 1 to give 4 and its reductive elimination. In telomer formation, a nucleophile reacts with butadiene to form the dimeric telomers in which the nucleophile is introduced mainly at the terminal position to form the 1-substituted 2,7-octadiene 5. As a minor product, the isomeric 3-substituted 1,7-octadiene 6 is formed[13,14]. The dimerization carried out in MeOD produces l-methoxy-6-deuterio-2,7-octadiene (10) as a main product 15]. This result suggests that the telomers are formed by the 1,6- and 3,6-additions of MeO and D to the intermediate complexes I and 2. 

Formic acid behaves differently. The expected octadienyl formate is not formed. The reaction of butadiene carried out in formic acid and triethylamine affords 1,7-octadiene (41) as the major product and 1,6-octadiene as a minor product[41-43], Formic acid is a hydride source. It is known that the Pd hydride formed from palladium formate attacks the substituted side of tt-allylpalladium to form the terminal alkene[44] (see Section 2.8). The reductive dimerization of isoprene in formic acid in the presence of Et3N using tri(i)-tolyl)phosphine at room temperature afforded a mixture of dimers in 87% yield, which contained 71% of the head-to-tail dimers 42a and 42b. The mixture was treated with concentrated HCl to give an easily separable chloro derivative 43. By this means, a- and d-citronellol (44 and 45) were pre-pared[45]. 

Active methylene or methine compounds, to which two EWGs such as carbonyl, alko.xycarbonyl, formyl, cyano, nitro, and sulfonyl groups are attached, react with butadiene smoothly and their acidic hydrogens are displaced with the 2,7-octadienyl group to give mono- and disubstituted compounds[59]. 3-Substituted 1,7-octadienes are obtained as minor products. The reaction is earned out with a /3-keto ester, /9-diketone, malonate, Q-formyl ketones, a-cyano and Q-nitro esters, cya noacetamide, and phenylsulfonylacetate. Di(octadienyl)malonate (61) obtained by this reaction is converted into an... 

Simple ketones and esters are inert. On the other hand, nitroalkanes react smoothly in r-butyl alcohol as a solvent with butadiene, and their acidic hydrogens are displaced with the octadienyl group. From nitromethane, three products, 64, 65, and 66, are formed, accompanied by 3-substituted 1,7-octadiene as a minor product. Hydrogenation of 65 affords a fatty amine 67 which has a primary amino function at the center of the long linear chain[46,61]. 

Some of the most difficult heterophase systems to characterize are those based on hydrocarbon polymers such as mbber-toughened polypropylene or other blends of mbbers and polyolefins. Eecause of its selectivity, RuO staining has been found to be usehil in these cases (221,222,230). Also, OsO staining of the amorphous blend components has been reported after sorption of double-bond-containing molecules such as 1,7-octadiene (231) or styrene (232). In these cases, the solvent is preferentially sorbed into the amorphous phase, and the reaction with OsO renders contrast between the phases. 

Linear dimeri2ation and oligomeri2ation of butadiene can be achieved by using a number of catalyst systems based on Pd, Ni (158—161), and Fe (162). 1,7-Octadiene can be obtained selectively when the dimeri2ation is carried out in the presence of a reducing agent such as formic acid (163—165) or H2/CO2 (166). 

Octadiene-3,5-diyne-l, 8-dimethoxy-9-octadecynoic acid Octogen (dry)... 

Deeatriene may, of course, react further to 1,5,9,13-tetradeca-tetraene, 1,5,9,13,17-octadecapentaene, etc. (18). Even the conjugated system 1,3-butadiene participates in metathesis reactions (14). An example of an intramolecular process is the reaction of 1,7-octadiene, which gives cyclohexene and ethene (13, 15) ... 

Consider the reaction of re/7-butoxyl radical with hydrocarbons such as 1, 7-octadiene, RH 7... 

Most importantly, the 4,5-diamino-1,7-octadienes 248a, 256 and 257, available by the double addition of allylic zinc reagents to the diimine 247, are... 

Scheme 43 Synthesis of enantiopure ring-substituted 1,2-diaminocyclohexanes by transition metal catalyzed and promoted cyclization of 1,7-octadienes...

Sugano et al. [561,562] explored the lipid model containing several different phospholipids, closely resembling the mixture found in reconstituted brush border lipids [433,566] and demonstrated dramatically improved property predictions. The best-performing lipid composition consisted of a 3% wt/vol lipid solution in 1,7-octadiene (lipid consisting of 33% wt/wt cholesterol, 27% PC, 27% PE, 7% PS, 7% PI). The donor and acceptor compartments were adjusted in the pH interval between 5.0 and 7.4 [562]. With such a mixture, membrane retention is expected to be extensive when lipophilic drugs are assayed. The use of 1,7-octadiene in the assay was noted to require special safety precautions. 

Five-lipid formula as reported by Sugano, except 1,7-octadiene was substituted with dodecane. 

The organoboron polymer complex was prepared as follows. First, poly(organoboron halide)55 was prepared according to the reported method, by hydroboration polymerization between 1,7-octadiene and the monobromoborane dimethylsuffide complex. The polymer obtained was then reacted with half an equivalent of methanol and 1-methylimidazole to give the corresponding copolymer efficiently (scheme 4). The structure of the polymer was characterized by H- and UB-NMR spectra. 

Similar nucleophiles have been found to react with butadiene to form dimeric telomers in which nucleophiles are introduced mainly at the terminal position to form 8-substituted 1,6-octadiene (17). As a minor product, 3-substituted 1,7-octadiene (18) is formed ... 

When PPh3 was added, a mixture of 1,7-octadiene (25) and 1,6-octadiene (24) was obtained (33). 1,7-Octadiene was obtained in 80% selectivity by using PdCl2(PPh3)2 and sodium propoxide as the catalyst system (34). 

The most characteristic reaction of butadiene catalyzed by palladium catalysts is the dimerization with incorporation of various nucleophiles [Eq. (11)]. The main product of this telomerization reaction is the 8-substituted 1,6-octadiene, 17. Also, 3-substituted 1,7-octadiene, 18, is formed as a minor product. So far, the following nucleophiles are known to react with butadiene to form corresponding telomers water, carboxylic acids, primary and secondary alcohols, phenols, ammonia, primary and secondary amines, enamines, active methylene compounds activated by two electron-attracting groups, and nitroalkanes. Some of these nucleophiles are known to react oxidatively with simple olefins in the presence of Pd2+ salts. Carbon monoxide and hydrosilanes also take part in the telomerization. The telomerization reactions are surveyed based on the classification by the nucleophiles. 

Primary alcohols react easily to form ethers. Reaction of methanol was carried out at 70°C using Pd(PPh3)2 (maleic anhydride) as a catalyst to give 8-methoxy-1,6-octadiene (36) (85%) accompanied by 3-methoxy-1,7-octadiene (37) (5%) and 1,3,7-octatriene (3%) (42). 

The reaction has been improved to a satisfactory process by modifying the reaction conditions. A remarkable effect of the addition of amines on the reaction was observed (49). For example, the reaction of butadiene (4 moles) and acetic acid (4 moles) in the presence of 2-(N,/V-dimethyl-amino)ethanol (4 moles) using Pd(acac)2 (3 mmoles) and PPh3 (3 mmoles) at 90°C gave complete conversion after 2 hours. The product was found to consist of 8-acetoxy-1,6-octadiene (47) (71%), 3-acetoxy-1,7-octadiene (48) (21%) and 1,3,7-octatriene (16) (8%). Various tertiary amines, such as triethylamine, )V-methylmorpholine, Af,Af,N, N -tetramethyl-1,3-bu-tanediamine, and triethylenediamine, showed the same favorable effect. Other basic salts, such as sodium and potassium acetate, accelerate the reaction, especially at high concentrations (50, 51). The selection of solvents is also important. Arakawa and Miyake found that electron-donating type solvents (e.g., THF and triethylamine) are good solvents... 

Few studies have been carried out on the telomerization of carboxylic acids other than acetic acid. Carboxylic acids are expected to react similarly with butadiene. The exception is formic acid No telomerization takes place, as described before (33, 34), and it behaves as a reductant rather than a nucleophile, forming 1,6- and 1,7-octadienes and octatriene. 

The mechanism of the reductive dimerization was studied by using both dideuterated and carboxyl-deuterated formic acid. The carboxyl deuterium was found on carbon 6, and the other deuterium on carbon 3 of 2,6-dimethyl-1,7-octadiene. 

The purpose in offering this rather complicated scheme was to rationalize the presence of minor amounts of 1-butene in the metathesis of 1,7-octadiene, thus requiring existence of a propylidene moiety. 

Metatheses of 1,7-octadienes containing various functional groups are catalysed by ruthenium carbene complexes of the type 248. For instance, the alcohol 249 (R = CH2OH), the aldehyde 249 (R = CHO) and the carboxylic acid 249 (R = CO2H) are all converted into the corresponding cyclohexenes 250 in 82-88% yields (equation 127) and the heterocycles 252 (n = 0, 1 or 2) are efficiently produced from the amides 251 (equation 128)123. 

Cyclopolymerization of Nonconjugated Dienes. Cyclopolymerization is an addition polymerization that leads to introduction of cyclic structures into the main chain of the polymer. Nonconjugated dienes are the most deeply studied monomers for cyclopolymerization and for cyclocopolymerizations with alkene monomers 66 In general, (substituted and unsubstituted) dienes with double bonds that are linked by less than two or more than four atoms cannot undergo efficient cyclization and result in crosslinked materials.12 In fact, efficient cyclopolymerization processes have been described, for instance, for a,oo-dienes like 1,5-hexadiene, 2-methyl-l,5-hexadiene, 1,6-heptadiene, and 1,7-octadiene,67 73 which lead to formation of homopolymers and copolymers containing methylene-1,3-cycloalkane units. 

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