Olefin acyclic

Ruthenium, and Osmium.—Acyclic Olefins. Matrix u.v. photolysis of (trimethylenemethane)Fe(CO)3 results in photodissociation of CO to yield the Fe(CO)2 species similar reactions are observed for (cbd)Fe(CO)3, (CeH6)Cr-(CO)3, and CpMn(CO)3. ESCA studies on (trimethylenemethane)Fe(CO)3 indicate a very positively charged central carbon in the trimethylenemethane group, consistent with previous calculations.  

Complex (54) has been obtained by reaction of 3,3-dimethylcyclopropene with Fe2(CO)9 the analogous CpMn(CO)(4,4-dimethylbuta-l,3-dienone) may be obtained on reaction with CpMn(CO)2THF. A crystal structure determination of (54) reveals a square pyramidal configuration. Reaction of a-allylnaph-thalene with Fes(CO)i2 results in isomerization to yield (55) a similar isomerization occurs on reaction of o -diallylbenzene to yield (56). A full paper on the reactions of the ligands (57) with iron carbonyls has appeared.  

Finally, a crystal structure determination of the [RuH( j -butadiene)(PMe2-Ph)a]+ cation reveals a distorted octahedral geometry with yhc-phosphine ligands (see also refs. 178—181). 

Cyclic Olefins. Molecular orbital calculations show that the trend of downfield shift for CO and upheld shift for hydrocarbon C resonances in the series 

Tricarbonyl iron complexes of a number of substituted dihydroanisic esters have been prepared. Several undergo hydride abstraction to yield [(cyclo-hexadienyl)Fe(CO)3]+ salts, which react with malonate in the expected manner to give the 5-substituted (l,3-chd)Fe(CO)3 derivative. Hydrolysis of the parent salt (63) yields (cyclohexa-2,4-dienone)Fe(CO)3 containing the keto-isomer of phenol, and (63) may also be alkylated with dimedone to yield the 5-substituted (l,3-chd)Fe(CO)s complex. The bicyclic analogue (64) and 

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It is also evident from the data of Bly et al. (95), Jacobs and Macomber (91), and Garry and Vessiere (99) that neopentyl-type homoallenic systems do not yield cyclopropyl derivatives upon solvolysis, in contrast to the unsubstituted parent system. If they have no substituents at Cj or C3, neopentyl homoallenic substrates yield rearranged acyclic olefins and rearranged solvent-incorporated products exclusively. If they carry an alkyl substituent at Ci, they give both rearranged and unrearranged acyclic products. If a substituent is present on C3 besides the acyclic derivatives, cyclobutyl products also are formed. 

Alkenes include aromatic, aliphatic, cyclic, acyclic olefins and unsaturated esters Scheme 28... 

Unlike the oxymercuration of acyclic olefins, oxymercuration of bicyclic olefins often gives jy -addition products. Norbornenes 93, for example, show exclusive fvo-oxymercuration. In this reaction, the ratio between the isomers depends on the nature of the fvo-substituent (R1) and tro/o-substituent (R2) (Equation (36)). The presence of electron-withdrawing fvo-substituents always leads to a much greater selectivity in favor of 94a-d over 95a-d.116 117 As indicated by extensive theoretical calculations, the charge distribution in the transition states governs the selectivity of these reactions.118... 

Triplet photoaddition of simple non-cyclic monoolefins is unknown. The sensitized dimerization of ethyl vinyl ether gives exclusively head-to-head adducts, Eq. 21, and probably should not be classed as an example of simple acyclic olefin. Usually the triplets have high energies and are severly twisted. 55> Some cyclic rigid molecules, Eq. 20, that do dimerize 63> do not incorporate substituents that allow regioselectivity to be determined. Butadiene gives principally head-to-head dimerization, Eq. 19, concordant with the PMO prediction, and so does indene, Eq. 22. The anti dimer that is formed would not be expected from a singlet excimer reaction. 

The formation of multinuclear clusters is much more favorable for rhodium than for cobalt. Additional evidence was obtained in comparative hydroformylation rate studies of 1-heptene and of cyclohexene at 75°C and 150 atm 1/1 H2/CO (19). For the acyclic olefin the kinetics followed the kinetic expression (except at low olefin) ... 

This process is quite unexpected for another reason. The cyclobutene ring is highly strained, making this monomer one of the most easily polymerized of all the cycloolefins. Thus, the variety of catalysts effective for cyclobutene polymerization is much broader than that effective for metathesis of low-strained cycloolefins and acyclic olefins (73). Therefore, the recovery of monomeric cyclobutene rather than its respective polymer is remarkable and indicates the lack of substantial metathesis activity in the above retrocarbenation system. 

With but few notable exceptions (75-77), an inherent characteristic of the metathesis of acyclic olefins with both homogeneous and heterogeneous catalysts is the tendency for attainment of thermodynamic equilibrium in the composition of cis and trans isomers in reactions carried to high conversion. Therefore, any inherent stereospecificity can only be evaluated by extrapolating compositional data to zero percent reaction. 

The diverse steric course of the metathesis of cyclic vs. acyclic olefins poses a dilemma. It stands to reason that once a cycloolefin monomer... 

In an attempt to further understand these observations, cis-directing catalysts for cyclopentene were examined in terms of their capability to metathesize acyclic olefins. 

Acyclic olefins act as chain scission agents in cycloolefin polymerization hence, they are employed as molecular weight regulators. Equations (48)-(50) illustrate the sequence by which chain scission is achieved ... 

The stereospecific catalysts capable of yielding high-cis polypentena-mers were found to be generally ineffective in metathesizing acyclic olefins. 

In summary, the interrelation of cis-selective catalysts and their lack of metathesis activity with acyclic olefins are rationalized by a speculative scheme that incorporates the concept of a tridentate cagelike complex as the active species of cis-directing catalysts. 

The formation of enantiopure tricyclic compounds takes place by intramolecular 1,3-dipolar cycloadditions of acyclic nitrones to cyclic olefinic fragments (Scheme 2.214a,b) (706, 707a), or of cyclic nitrones to acyclic olefins (Scheme 2.214c) (116). Recently (707),b intramolecular nitrone cycloaddition reactions (according to Scheme 2.211a) have been applied in the synthesis of... 

Recently, Nicolaou and coworkers have devised a novel, one-pot strategy for the direct transformation of acyclic olefinic esters to cyclic enol ethers [34]. Unlike the molybdenum alkylidene 1 (see Sect. 3.2), initial reaction between the Tebbe reagent 93 and an olefinic ester results in rapid carbonyl olefination to afford a diene intermediate. Subsequent heating initiates RCM to afford the desired cyclic product (Scheme 17). 

Li et al. (1997) have discussed the use of catalytic antibodies to control the reactivity of carbocations. At an entry level, the acyclic olefinic sulfonate ester [72] is converted into the cyclic alcohol [73] (98%) using antibody 4C6 raised to hapten [73] with only 2% of cyclohexene produced (Appendix entry 15.1) (Li et al, 1994). 

The same authors later on presented their results of the epoxidation of various cyclic and acyclic olefins employing a heterogeneous catalyst with an oxovanadium(IV) ion incorporated on a sulfonic acid ion-exchange resin and TBHP as oxidant . Selectivities... 

The telomerization of butadiene by means of water in ILs was described by Dullius et Rottger et al. report a process for the telomerization of acyclic olefins having at least two conjugated double bonds, or their mixtures, using a palladium-carbene complex as catalyst in an IL solvent. The nucleophiles included water, alcohols, phenols, polyols, carboxylic acids, ammonia and primary and secondary amines. The acycylic olefins could be either 1,3-butadiene or isoprene. 

The literature on liquid-phase olefin oxidation has been well reviewed (1, 2, 3, 5, 6, 8,12,14,15, 16,17, 18,19,20). Recent attention has been focused on the effects of structure and reaction conditions on the proportions of alkenyl hydroperoxy radical reaction by the abstraction and addition mechanisms at lower temperatures and conversions. The lower molecular weight cyclic and acyclic olefins have been extensively studied by Van Sickle and co-workers (17, 18, 19, 20). These studies have recently been extended to include higher molecular weight alkenes (16). 

Allylic hydroperoxides are primary products in the autoxidation of - olefins, and lack of definite information on their reactivity and chemical behavior has hampered efforts to understand olefin oxidation mechanisms (2). This deficiency is most strongly felt in determining the relative rates of addition and abstraction mechanisms for acyclic olefins since assignment of secondary reaction products to the correct primary source is required. Whereas generalizations about the effect of structure on the course of hydroperoxide decompositions are helpful, most questions can be answered better by directly isolating the hydroperoxides involved and observing the products formed by decomposition of the pure compounds. 

The same inefficiencies occur in the photocycloaddition reaction of carbonyl compounds with high-energy triplets to acyclic olefins (Table VIII). Here, the olefin triplet presumably deactivates before dimerization can occur. 

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