Cyclohexane formation

Cyclohexane Formation Using Diels-Alder Cycloaddition [214]... 

The high diastereoselectivity found on base-promoted cyclization of ethyl 7-bromo-2-methylheptenoates (bearing 3-, 4- or 6-methyl substituents) has been attributed to folding strain control of incipient cyclohexane formation.40 The selectivity is only moderate for the 5-methyl substrate but increases with the bulk of the substituent Ph < Me Et < z -Pr < r-Bu. 

Cyclohexane, formation of. in reaction of cvdohexvl iodide with sodium nitrite 220... 

In cyclohexane, formation of norbomane, and R — H from a general point of view, is explained by the chain mechanism described on Scheme 14. 

Cyclohexane formation is entropically less favorable than cyclopentane generation, and treatment of 1,6-dienes under the conditions listed in Eq. (47) leads to the production of uncyclized, disilylated products (Eq.49) [35] or silicon bridged dimers [40]. To avoid these problems, phenylmethylsilane can be employed as the chain terminator. Utilizing this more hindered silane slows the o-bond metathesis sufficiently to prevent dimerization (Eq. 50). The trapping step can be retarded even further by the use of diphenylsilane (Eq. 51). Thus, not only can the metal and the ligand array be manipulated to bring about the desired result in the catalytic process, but the properties of the silane reagent itself can also be adjusted to meet the demands of the synthesis at hand. 

We have estimated the stationary concentration of R as 10 M from the dependence of the rate of cyclohexane formation on the CCl concentration. 

Figure 8 Turnover rates of cyclohexene and cyclohexane formation during the hydrogenation of benzene on Pt(lll) and Pt(lOO) surfaces a), as well as the cubic and cuboctahedra platinum nanoparticles b), which demonstrate the similarities between the single-crystal and nanoparticle surfaces. CHA=cyclohexane, CHE=cyclohexene. Reproduced from Reference 42 with kind...

Cyclohexane formation is not restricted to 1,6-addition of an allylsilane to a dienone. Equation 10 contains two examples whereby a lengthy tether linking the reactive functionalities leads to cyclohexane annulation via 1,4-conjugate addition. 

FIGURE 14.7 The activation energy barrier for cyclohexane formation is high and makes this reaction difficult under normal conditions. 

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