Reactions of Diolefins

Formation of Stable Adducts with Pd(ll)-Carbon a Bonds 

The chemistry of diolefin n complexes of Pd(II) has a special place in the catalytic chemistry of Pd(II) because their reactions with nucleophiles gave adducts that served as stable models for the types of unstable intermediates postulated in many reactions of Pd(II) with olefins. 

The first oxypalladation adducts from dienes were obtained by the reaction of dienes in basic alcohol media 

The gross structural features of this type of complex were first postulated by Chatt et al. 34) and later confirmed by X-ray studies for the platinum(II) analogs 211, 291). In this type of complex, the OR group is trans to the Pd(II), with the alkoxy group exo and the Pd(II) endo. Adducts have also been prepared in which the nucleophile is an acetate or a carbanoid species such as malonate or acetoacetate 180). 

A number of new adducts have been reported recently with a variety of nucleophiles. Benzylamine gives an adduct with the 1,5-cyclooctadiene PdClg-ir complex which is a tetramer because of intermolecular N-Pd bonds (7), 

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Ohta, T. (1984) Rate constants for the reactions of diolefins with OH radicals in the gas phase. Estimate of the rate constants from those for monoolefins. J. Phys. Chem. 87, 1209-1213. 

The reaction of diolefins with aromatics is similar to that of styrenes with aromatics. Hoffman and Michael (44) reported that toluene and various conjugated diolefins could be reacted at 60-90 in the presence of sodium to yield alkenylbenzenes [Reaction (25)]. 

The electron transfer photosensitized reactions of diolefins results in the formation of [4 + 2]cycloadducts. For example, irradiation of octafluoronaphtha-lene [129] or dicyanoanthracene [130-132] in polar solvents containing cyclohexa-diene leads to the formation of endo- and exo-dicyclohexadiene. 

The reaction of diolefins in the alkylation unit results in the formation of undesirable products diphenyl alkanes, polymers, and indane/tetralins (Fig. 3). The first two result in yield loss, while the third lowers product quality. Selective hydrogenation can be used to convert diolefins to mono-olefins. The UOP DeFine process was commercialized for this purpose in 1986. Use of the DeFine process in LAB production results in approximately 50% reduction in the formation of heavy alkylate and approximately 5% increase in LAB yield. The reaction takes place over... 

Our investigations show that 1,4-disubsituted butadiene derivatives react in layered structures under exclusive formation of 1,i-trans-polymers. A stereoregular polymer is obtained. The structure analyses of the monomer and polymer crystals of 1 show that a lattice-controlled reaction takes place. It is certainly worthwhile studying the course of the reaction more in detail, and to compare the reaction mechanism and kinetics with those of other lattice-controlled reactions, as, for example, the polymerization reactions of diolefin 12Z) and butadiyne derivatives (23). 

This review article is concerned with chemical behavior of organo-lithium, -aluminum and -zinc compounds in initiation reactions of diolefins, polar vinyls and oxirane compounds. Discussions are given with respect to the following five topics 1) lithium alkylamide as initiator for polymerizations of isoprene and 1,4-divinylbenzene 2) initiation of N-carboxy-a-aminoacid anhydride(NCA) by a primary amino group 3) activated aluminum alkyl and zinc alkyl 4) initiation of stereospecific polymerization of methyloxirane and 5) comparison of stereospecific polymerization of methyloxirane with Ziegler-Natta polymerization. A comprehensive interpretation is proposed for chemistry of reactivity and/or stereospecificity of organometallic compounds in ionic polymerizations. 

This review article is concerned with chemical behavior of organo-lithium, -aluminum and -zinc compounds in initiation reactions of diolefins, polar vinyls and oxirane compounds. A comprehensive interpretation is proposed for metallic compounds in ionic polymerizations. 

Polysulfones by the reaction of diolefin polymers with sulfur dioxide [70,71]. 

The reaction of OF2 and various unsaturated fluorocarbons has been examined (35,36) and it is claimed that OF2 can be used to chain-extend fluoropolyenes, convert functional perfluorovinyl groups to acyl fluorides and/or epoxide groups, and act as a monomer for an addition-type copolymerization with diolefins. 

The reaction of dihalocarbenes with isoprene yields exclusively the 1,2- (or 3,4-) addition product, eg, dichlorocarbene CI2C and isoprene react to give l,l-dichloro-2-methyl-2-vinylcyclopropane (63). The evidence for the presence of any 1,4 or much 3,4 addition is inconclusive (64). The cycloaddition reaction of l,l-dichloro-2,2-difluoroethylene to isoprene yields 1,2- and 3,4-cycloaddition products in a ratio of 5.4 1 (65). The main product is l,l-dichloro-2,2-difluoro-3-isopropenylcyclobutane, and the side product is l,l-dichloro-2,2-difluoro-3-methyl-3-vinylcyclobutane. When the dichlorocarbene is generated from CHCl plus aqueous base with a tertiary amine as a phase-transfer catalyst, the addition has a high selectivity that increases (for a series of diolefins) with a decrease in activity (66) (see Catalysis, phase-TRANSFEr). For isoprene, both mono-(l,2-) and diadducts (1,2- and 3,4-) could be obtained in various ratios depending on which amine is used. 

Paraffins are relatively inactive compared to olefins, diolefins, and aromatics. Few chemicals could be obtained from the direct reaction of paraffins with other reagents. However, these compounds are the precursors for olefins through cracking processes. The C -Cg paraffins and cycloparaffms are especially important for the production of aromatics through reforming. This section reviews some of the physical and chemical properties of C1-C4 paraffins. Long-chain paraffins normally present as mixtures with other hydrocarbon types in different petroleum fractions are discussed later in this chapter. 

The catalytic system used in the Pacol process is either platinum or platinum/ rhenium-doped aluminum oxide which is partially poisoned with tin or sulfur and alkalinized with an alkali base. The latter modification of the catalyst system hinders the formation of large quantities of diolefins and aromatics. The activities of the UOP in the area of catalyst development led to the documentation of 29 patents between 1970 and 1987 (Table 6). Contact DeH-5, used between 1970 and 1982, already produced good results. The reaction product consisted of about 90% /z-monoolefins. On account of the not inconsiderable content of byproducts (4% diolefins and 3% aromatics) and the relatively short lifetime, the economics of the contact had to be improved. Each diolefin molecule binds in the alkylation two benzene molecules to form di-phenylalkanes or rearranges with the benzene to indane and tetralin derivatives the aromatics, formed during the dehydrogenation, also rearrange to form undesirable byproducts. 

Of further particular interest was that the crystallographic results on 2,5-DSP and poly-2,5-DSP had pointed out a very important future possibility that an absolute asymmetric synthesis could be achieved if any prochiral molecule, e.g. an unsymmetrical diolefin derivative, could be crystallized into a chiral crystal and if the reaction of the chiral crystal proceeded in the same manner as the 2,5-DSP crystal with retention of the crystal lattice (Wegner, 1972, 1973). Such types of absolute asymmetric synthesis with a high enantiomeric yield have now been performed by topochemical [2+2] photoreaction of unsymmetric diolefin crystals (Addadi etal., 1982 Hasegawa et al., 1990 Chung et al., 1991a,b). 

In this chapter the topochemical [2+2] photoreactions of diolefin crystals are reviewed from the viewpoints of organic photochemistry, analysis of reaction mechanism, and crystallography as well as in terms of synthetic polymer chemistry and polymer physics. 

Recently several examples of diolefin crystals in which the reaction behaviour deviates from the topochemical rule have been observed. For example, in the photoreaction of methyl a-cyano-4-[2-(4-pyridyl)-ethenyljcinnamate (2 OMe), the first reaction occurs exclusively at the pyridyl side although the distance between the ethylenic double bonds on the pyridyl side is exactly the same as that between the ethylenic double bonds on the ester side (4.049 A), as shown in Fig. 5 (Maekawa et al., 1991a). A few other unsymmetrical diolefin compounds display the same regioselective behaviour (Hatada, 1989). 

It is well known that the [2+2] photodimerization of diolefinic compounds is allowed to occur photochemically but not thermally, whereas the cyclobutane cleavage reaction occurs both photochemically and thermally. The cleavage reaction occurs with irradiating light of shorter wavelength... 

On the other hand, the crystallization process of diolefin compounds often plays a significant role in determining their topochemical behaviour, by changing their crystal structure or by forming solvent inclusion complexes. Furthermore, topochemical photoreactions of crystals with )8-type packing are accompanied by thermal processes under moderate control by the reacting crystal lattice (see p. 140). These factors seriously complicate the whole reaction scheme. 

Along with the guidepost (Wegner, 1972, 1973) based on the crystal-to-crystal transition from 2,5-DSP to poly-2,5-DSP, absolute asymmetric synthesis has been achieved by the topochemical reaction of a chiral crystal of an achiral diolefin compound in the absence of any external chiral reagents. 

This is the first example of a topochemical reaction of a molecular complex of a perfectly ordered polymer composite. Complex 2,5-DSP-l OEt is also obtained by simple grinding of homocrystals 2,5-DSP and l OEt, as is observed for the pair of diolefinic compounds described on p. 166. 

By 1990, most of the catalytic reactions of TS-1 had been discovered. The wide scope of these reactions is shown in Fig. 6.1.35 Conversions include olefins and diolefins to epoxides,6,7 12 16 19 21 24 34 36 38 13 aromatic compounds to phenols,7,9 19 25 27 36 ketones to oximes,11 20 34 46 primary alcohols to aldehydes and then to acids, secondary alcohols to ketones,34-36 42 47-30 and alkanes to secondary and tertiary alcohols and ketones.6 34 43 31 52... 

It is generally observed that the less hindered double bond in a diolefin is preferentially hydrogenated as found in the reaction of limonene (equation 16)56. 

Pines and Csicsery reported on the formation of diolefins in chromia catalyzed dehydrocyclization of Cj-Cg hydrocarbons 49). The kinetic behavior of heptadienes and heptatrienes in chromia and molybdena catalyzed aromatization of unsaturated n-Cj hydrocarbons 22, 49a) indicated that they were intermediates of the reaction. 

Catalysts lacking phosphorus ligands have also been used as catalysts for allylic substitutions. [lr(COD)Cl]2 itself, which contains a 7i-accepting diolefin ligand, catalyzes the alkylation of allylic acetates, but the formation of branched products was only favored when the substitution reaction was performed with branched allylic esters. Takemoto and coworkers later reported the etherification of branched allylic acetates and carbonates with oximes catalyzed by [lr(COD)Cl]2 without added ligand [47]. Finally, as discussed in Sect. 6, Carreira reported kinetic resolutions of branched allylic carbonates from reactions of phenol catalyzed by the combination of [lr(COE)2Cl]2 and a chiral diene ligand [48]. 

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