Olefin acyclic cyclic

The estimates of the RSE for small cyclic alkanes, cyclo-olefins, and cyclic ethers using all three reactions are listed in Table 3.21. The failure of the isodesmotic reaction is readily apparent by examining the RSE of the cyclic alkanes. For the rings having five or more carbon atoms, the isodesmic method predicts that there is no strain energy. Rather, it predicts that these cyclic species are more stable than their acyclic counterparts. The homodesmotic and GE reactions, which are identical for the cyclic alkanes, provide RSEs in excellent agreement with CRSE estimates. 

AUylic oxidation. Cyclohexene is oxidized to cyclohex-2-enyl acetate in 75% yield by the reagent at 70° when catalyzed by potassium bromidefea. 8 hr.). The reaction is slow in the absence of a catalyst. Norbomene is unreactive, but bicyclo[3.2.noclene-2 is oxidized rapidly to about an equal mixture of endo- and cxo-bicycIo[3.2.1]oct-3-ene-2-yl acetates. Acyclic olefins or cyclic olefins prone to allylic rearrangement give a complex mixture of allylic acetates. 

There are some examples known for the cycloaddition of azomethine ylides with nonactivated olefins such as aryl-substituted olefins, strained olefins, acyclic or cyclic olefins, and electron-rich olefins. Stabilized ylide 79 (R = H, R = Et, R = Me), bearing an ester moiety as the only C substituent, can be successfully trapped with styrene when generated by the deprotonation route (Section II,D) from ethyl sarcocinate and paraformaldehyde under reflux in toluene, to give 194 as a mixture of two regioisomers (86CL973). 

Chiral olefins (racemic or enantiomerically pure) can provide two diastcreomers when carbene (carbenoid) CX2 is added, or four diastereomers when carbene (carbenoid) CXY is employed. Cyclic alkenes (on-ring stereoselection) are considered before acyclic olefins (acyclic stcrcosclcction) are discussed. 

Olefins - Acyclic and cyclic hydrocarbons having one or more carbon-carbon double bonds, apart from the formal ones in aromatic compounds. The class olefins subsumes alkenes and cycloalkenes and the corresponding polyenes. [5]... 

The ozonolysis of acyclic alkenes including terpenes is reviewed in Ref. [85]. The role of ozonolysis as ecological process for the selective and specialized oxidation of petrochemical olefins and cyclic alkenes, for the manufacture of biologically active substances and normal organic compounds is thoroughly discussed in Ref. [86],... 

As with both terminal and cyclic olefins containing vinylic chlorine or bromine, acyclic counterparts partly lose the halogen first and then undergo dihydrogenation to the tetrahydro dcnvative [54] (equation 44) When the reachon IS earned out in the hquid phase in the presence of base, yields of tetrahydro product are enhanced [55] (equation 44)... 

The thermolysis of xanthates derived from primary alcohols yields one olefin only. With xanthates from secondary alcohols (acyclic or alicyclic) regioisomeric products as well as fi/Z-isomers may be obtained see below. While acyclic substrates may give rise to a mixture of olefins, the formation of products from alicyclic substrates often is determined by the stereochemical requirements the /3-hydrogen and the xanthate moiety must be syn to each other in order to eliminate via a cyclic transition state. 

Acyclic diene molecules are capable of undergoing intramolecular and intermolec-ular reactions in the presence of certain transition metal catalysts molybdenum alkylidene and ruthenium carbene complexes, for example [50, 51]. The intramolecular reaction, called ring-closing olefin metathesis (RCM), affords cyclic compounds, while the intermolecular reaction, called acyclic diene metathesis (ADMET) polymerization, provides oligomers and polymers. Alteration of the dilution of the reaction mixture can to some extent control the intrinsic competition between RCM and ADMET. 

Acyclic sulfoxides fragment into olefins and sulfenic acids on thermolysis97. Cyclic sulfoxides exhibit essentially the same ready mode of fragmentation106. 

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

In the presence of a suitably disposed /i-hydrogen—as in alkyl-substituted thiirane oxides such as 16c—an alternative, more facile pathway for thermal fragmentation is available . In such cases the thiirene oxides are thermally rearranged to the allylic sulfenic acid, 37, similarly to the thermolysis of larger cyclic and acyclic sulfoxides (see equation 9). In sharp contrast to this type of thiirane oxide, mono- and cis-disubstituted ones have no available hydrogen for abstraction and afford on thermolysis only olefins and sulfur monoxide . However, rapid thermolysis of thiirane oxides of type 16c at high temperatures (200-340 °C), rather than at room temperature or lower, afforded mixtures of cis- and trans-olefins with the concomitant extrusion of sulfur monoxide . The rationale proposed for all these observations is that thiirane oxides may thermally... 

The reductive elimination of a variety of )3-substituted sulfones for the preparation of di-and tri-substituted olefins (e.g. 75 to 76) and the use of allyl sulfones as synthetic equivalents of the allyl dianion CH=CH—CHj , has prompted considerable interest in the [1,3]rearrangements of allylic sulfones ". Kocienski has thus reported that while epoxidation of allylic sulfone 74 with MCPBA in CH2CI2 at room temperature afforded the expected product 75, epoxidation in the presence of two equivalents of NaHCOj afforded the isomeric j ,y-epoxysulfone 77. Similar results were obtained with other a-mono- or di-substituted sulfones. On the other hand, the reaction of y-substituted allylic sulfones results in the isomerization of the double bond, only. The following addition-elimination free radical chain mechanism has been suggested (equations 45, 46). In a closely related and simultaneously published investigation, Whitham and coworkers reported the 1,3-rearrangement of a number of acyclic and cyclic allylic p-tolyl sulfones on treatment with either benzoyl peroxide in CCI4 under reflux or with... 

Some remarks concerning the scope of the cobalt chelate catalysts 207 seem appropriate. Terminal double bonds in conjugation with vinyl, aryl and alkoxy-carbonyl groups are cyclopropanated selectively. No such reaction occurs with alkyl-substituted and cyclic olefins, cyclic and sterically hindered acyclic 1,3-dienes, vinyl ethers, allenes and phenylacetylene95). The cyclopropanation of electron-poor alkenes such as acrylonitrile and ethyl acrylate (optical yield in the presence of 207a r 33%) with ethyl diazoacetate deserve notice, as these components usually... 

The Heck reaction, a palladium-catalyzed vinylic substitution, is conducted with olefins and organohalides or pseudohalides are frequently used as reactants [15, 16], One of the strengths of the method is that it enables the direct monofunctionalization of a vinylic carbon, which is difficult to achieve by other means. Numerous elegant transformations based on Heck chemistry have been developed in natural and non-natural product synthesis. Intermolecular reactions with cyclic and acyclic al-kenes, and intramolecular cyclization procedures, have led to the assembly of a variety of complex and sterically congested molecules. 

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. 

Differences in reactivity have been exhibited between acyclic and different types of cyclic olefins. Vinylcyclohexene in a cobalt hydroformylation at 120°-134°C and 475-720 atm pressure gave a 65% yield of a mixture of mono- and dialdehydes (66). 

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

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... 

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