Methylenecyclohexane Methylene group

However, owing to the lack of j8-hydrogen in the intermediate metallacycle, 1,1-disubstituted ethylenes (2-methylpropene, methylenecyclohexane) do not undergo )S-hydrogen transfer instead, their methylene group is catalytically exchanged by a degenerated olefin metathesis reaction ... 

Methylcyclohexanol, dehydration of, 183 1-Methylcyclopentene addition of hydrogen chloride, 215 hydroboration-oxidation, 230-233 Methylenecyclohexane, 677 Methylene group, 57 prefix, 170... 

The effect of introducing sp -hybridized atoms into open-chain molecules has been discussed previously, and it has been noted that the torsional barriers in 1-alkenes and in aldehydes and ketones are smaller than those in alkanes. Similar properties carry over to incorporation of sp centers in six-membered rings. Whereas the free energy of activation for ring inversion in cyclohexane is 10.3 kcal/mol, the barrier is reduced to 7.7 kcal/mol in methylenecyclohexane, and to 4.9 kcal/mol in cyclohexanone." The decrease in activation energy is related to the lower torsional barriers for rotation about sp -sp bonds, and to the decreased steric requirements of a carbonyl or methylene group. 

Exchange of methylene groups (degenerate metathesis) has been studied using methylenecyclohexane and CH2=C(CH3)2 with [iri -C5H5)Ti(CH2)AlCl(CH3)2]... 

As a further application of the reaction, the conversion of an endocyclic double bond to an c.xo-methylene is possible[382]. The epoxidation of an cWo-alkene followed by diethylaluminum amide-mediated isomerization affords the allylic alcohol 583 with an exo double bond[383]. The hydroxy group is eliminated selectively by Pd-catalyzed hydrogenolysis after converting it into allylic formate, yielding the c.ro-methylene compound 584. The conversion of carvone (585) into l,3-disiloxy-4-methylenecyclohexane (586) is an example[382]. 

In the presence of methanol as solvent and 1,4-dicyanobenzene as acceptor, photoinduced electron transfer from 1,4-bis(methylene)cyclohexane gives 4-(methoxymethyl)-1 -methylenecyclohexane and 4-(4-cyanophenyl)-4-(methoxy-methyl)-l-methylenecyclohexane which arise by nucleophilic attack of the solvent on the radical cations, followed either by reduction and protonation, or by combination with the radical anion of the electron acceptor.These observations are in accordance with the proposed mechanism of the nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction. The same group has also investigated the use of cyanide ion as nucleophile and report that irradiation of a mixture of 1,4-dicyanobenzene in the presence of biphenyl as donor, KCN, and 18-crown-6 gives a mixture of (79) and (80). These workers have also extended the scope of NOCAS to fluoride ion. In particular, use of 2,3-dimethylbut-2-ene and 2-methylbut-2-ene gives 4-cyanophenyl substituted... 

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