Cycloalkenes compounds

Cross-metathesis of Alkyne with Cycloalkene (ROM-CM-RCM Sequence) A cascade metathesis with cycloalkene compounds is an interesting reaction because the different ring-size cyclic diene is formed from the starting cycloalkene via multiple processes in... 

When applying this principle to replacement names generated from fusion nomenclature, it is essential to keep in mind that fusion names for hydrocarbons ending in -cycloalkene are for fully unsaturated skeletons the -ene ending implies whatever number of double bonds may be necessary, without a multiplier. Thus (117) has six double bonds in the twelve-membered ring, and one must add ten hydrogens to saturate it to the stage of a simple benzene derivative, compound (118). 

Oxidative reactions frequently represent a convenient preparative route to synthetic intermediates and end products This chapter includes oxidations of alkanes and cycloalkanes, alkenes and cycloalkenes, dienes, aromatic fluorocarbons, alcohols, phenols, ethers, aldehydes and ketones, carboxylic acids, nitrogen compounds, and organophosphorus, -sulfur, -selenium, -iodine, and -boron compounds... 

Terminally unsaturated fluonnated alkenoic acids can be obtained from poly-fluorocycloalkenes by reaction with potassium hydroxide m rert-butyl alcohol [24] (equation 26) The use of a tertiary alcohol is critical because primary and secondar y alcohols lead to ethers of the cycloalkenes The use of a polar aprotic solvent such as diglyme generates enols of diketones [26] (equation 27) The compound where... 

Calculate energy differences between cis and trans-cycloheptene and cis and trans-cyclooctene. Which is the more stable isomer for each compound Is there a significant (>.008 au or 5 kcal/mol) increase in the energy difference between cis and trans isomers in going from the seven to eight-membered cycloalkene Are your results consistent with the fact that trans-cyclooctene is an isolable, stable compound while trans-cycloheptene is not ... 

Compare geometries of the cis and trans cycloalkenes. Are the double bonds incorporated into the trans compounds significantly more distorted than those incorporated into the analogous cis cycloalkenes Consider carbon-carbon bond lengths and the twisting and/ or puckering of the double bond. Are any distortions greater in trans-cycloheptene than in trans-cyclooctene ... 

Alicyclic Hydrocarbons. These refer to cyclic analogues of aliphatic hydrocarbons and are named accordingly, using the piefix cyclo-." Their properties are similar to their open-chain aliphatic counterparts. Alicyclic hydrocarbons are subdivided into monocyclic (cycloalkanes, cycloalkenes, cycloalkynes, cycloalkadienes, etc.) and polycyclic aliphatic compounds. Monocyclic aliphatic structures having more than 30 carbon atoms in the ring are known, but those containing 5 or 6 carbon atoms are more commonly found in nature [47, p. 28]. 

Cycloalkenes and cyclohexadienes. These unsaturated cyclic aliphatic compounds [49, p. 284] have one and two double bonds, respectively, in the ring. Eixamples are... 

Since then, the metathesis reaction has been extended to other types of alkenes, viz. substituted alkenes, dienes and polyenes, and to alkynes. Of special interest is the metathesis of cycloalkenes. This gives rise to a ring enlargement resulting in macrocyclic compounds and eventually poly-... 

Mutual metathesis of a cyclic and an acyclic alkene provides still more possibilities in synthesizing organic compounds. For instance, cycloalkenes are cleaved by ethene into a,co-dienes. The reaction of 1,5-cyclooctadiene with ethene gives 1,5,9-decatriene (18) norbornene reacts with 2-butene to yield 1,3-dipropenylcyclopentane (30) ... 

More research efforts have focused on the ring-closing enyne metathesis, which usually [176] provides conjugated vinyl cycloalkenes (cf Fig. 2a, exo mode) useful for further manipulation, but also allows tandem metathesis processes for the formation of polycyclic compounds. 

An obvious drawback in RCM-based synthesis of unsaturated macrocyclic natural compounds is the lack of control over the newly formed double bond. The products formed are usually obtained as mixture of ( /Z)-isomers with the (E)-isomer dominating in most cases. The best solution for this problem might be a sequence of RCAM followed by (E)- or (Z)-selective partial reduction. Until now, alkyne metathesis has remained in the shadow of alkene-based metathesis reactions. One of the reasons maybe the lack of commercially available catalysts for this type of reaction. When alkyne metathesis as a new synthetic tool was reviewed in early 1999 [184], there existed only a single report disclosed by Fiirstner s laboratory [185] on the RCAM-based conversion of functionalized diynes to triple-bonded 12- to 28-membered macrocycles with the concomitant expulsion of 2-butyne (cf Fig. 3a). These reactions were catalyzed by Schrock s tungsten-carbyne complex G. Since then, Furstner and coworkers have achieved a series of natural product syntheses, which seem to establish RCAM followed by partial reduction to (Z)- or (E)-cycloalkenes as a useful macrocyclization alternative to RCM. As work up to early 2000, including the development of alternative alkyne metathesis catalysts, is competently covered in Fiirstner s excellent review [2a], we will concentrate here only on the most recent natural product syntheses, which were all achieved by Fiirstner s team. 

As previously mentioned, double bonds in relatively small rings must be cis. A stable trans double bond first appears in an eight-membered ring trans-cyclooctene, p. 134), though the transient existence of tran -cyclohexene and cycloheptene has been demonstrated. Above 11 members, the trans isomer is more stable than the cis. It has proved possible to prepare compounds in which a trans double bond is shared by two cycloalkene rings (e.g., 104). Such compounds have been called [m.n]betweenanenes, and several have been prepared with m and n values from 8 to 26. The double bonds of the smaller betweenanenes, as might be... 

Almost all evidence indicates that the transition state must be planar. Deviations from planarity as in 17-3 (see p. 1322) are not found here, and indeed this is why six-membered heterocyclic nitrogen compounds do not react. Because of the stereoselectivity of this reaction and the lack of rearrangement of the products, it is useful for the formation of trans cycloalkenes (eight-membered and higher). 

K or Li, as well as with Zn—Me3SiCl and with certain compounds prepared from WCle and either lithium, lithium iodide, LiAlH, or an alkyllithium (see 17-17). The reaction has been used to convert dialdehydes and diketones to cycloalkenes. Rings of 3-16 and 22 members have been closed in this way, for example. 

The present procedure for ring expansion has also been applied to l,2-bis(trimethylsilyloxy)bicyclo[n.l.0]alkanes, which are prepared by cyclopropanation of l,2-bis(silyloxy)cycloalkenes. The latter are readily available from acyloin condensations in the presence of chlorotrimethylsilane. " This reaction provides a new route to cyclic 1,3-diketones and macrocyclic compounds containing two 1,3-diketone units in the ring. 

Another important feature of this reaction is the synthesis of highly strained E-cycloalkenes. Thus E,Z-cycloocta-1,3-diene has been obtained from the Z,Z-compound in sensitized irradiation 309) (3.4), while E-cyclo-octene was obtained from the Z-isomer by direct irradiation (3.5) 310). The synthesis of a trans doubly bridged olefin has also been reported (3.6)311>. 

Cycloaddition with nitrile oxides occur with compounds of practically any type with a C=C bond alkenes and cycloalkenes, their functional derivatives, dienes and trienes with isolated, conjugated or cumulated double bonds, some aromatic compounds, unsaturated and aromatic heterocycles, and fullerenes. The content of this subsection is classified according to the mentioned types of dipolarophiles. Problems of relative reactivities of dienophiles and dipoles, regio- and stereoselectivity of nitrile oxide cycloadditions were considered in detail by Jaeger and... 

The ternary diagram in Figure 4 shows the composition of crude oil samples based on the content of normal plus isoalkenes (parafliins), cycloalkenes (naphtenes), and aromatic hydrocarbons plus polar, heteroatomic compounds (NSO). 

Not unexpectedly, cycloalkene oxides are equally important as alkene oxides in medicinal chemistry and drug metabolism, as illustrated below with a few selected examples. Other compounds of interest that will not be discussed here include epoxytetrahydrocannabinols and endogenous 16,17-ep-oxy steroids. 

Automotive gasoline contains 150 or more different chemical compounds and the relative concentrations of the compounds vary considerably, depending on the source of crude oil, refinery process, and product specifications. Typical hydrocarbon constituents are (volume basis) alkanes (4 to 8%), alkenes (2 to 5%), isoalkanes (25 to 40%), cycloalkanes (3 to 7%), cycloalkenes (1 to 4%), and aromatics (20 to 50%). However, these proportions vary greatly. 

Cycloalkenes such as cyclohexene, 1-methylcyclohexene, cyclopentene, and nor-bornene are hydrosilylated with triethylsilane in the presence of aluminum chloride catalyst in methylene chloride at 0 °C or below to afford the corresponding hydrosilylated (triethylsilyl)cycloalkanes in 65-82% yields [Eq. (23)]. The reaction of 1-methylcyclohexene with triethylsilane at —20 °C occurs regio- and stereoselectively to give c/i-l-triethylsilyl-2-methylcyclohexane via a tra x-hydrosilylation pathway. Cycloalkenes having an alkyl group at the double-bonded carbon are more reactive than non-substituted compounds in Lewis acid-catalyzed hydrosilylations. ... 

ROM-RCM of cycloalkene-yne 119 having a substituent at the 3-position of the cycloalkene would give a polymer because ruthenium carbene complex XVlll generated in this reaction could react with the starting alkyne. If this reaction is carried out under ethylene gas, the cyclized compound 120 should be formed by the reaction of XVlll with ethylene [Eq. (6.88)]. On the basis of this idea, ROM-RCM-CM of cycloalkene-yne 119 was carried out under ethylene gas " ... 

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