Norcarane from cyclohexene

Current interest in cyclopropanes is reflected by two preparations Norcarane from cyclohexene, methylene iodide, and zinc-copper couple (p. 72) illustrates a new way of adding a methylene... 

Methylene iodide and a zinc-copper couple react in ether solution to give bis-(iodomethyl)zinc zinc iodide . Closely related reagents are accessible by the reaction of zinc halides with diazomethane . These reagents have been widely used in the synthesis of cyclopropanes from olefins. Norcarane formation from cyclohexene and bis(iodomethyl)zinc was found to be second order, k = (6.3 0.5) x 10 l.mole . sec " at 0°C These findings cannot be reconciled with the intermediacy of free methylene. A one-step methylene transfer mechanism has therefore been proposed for the Simmons-Smith reaction, viz. 

The thermal decomposition of diazo(phenylsulfonyl)methane 223 under a nitrogen atmosphere generates phenylsulfonylcarbene which is trapped by olefin such as cyclohexene to give norcaranes 224 and 225 (equation 138)132. No cycloheptatriene derivative is isolated from the thermolysis of223 in benzene133. In contrast, intramolecular insertion of sulfonylcarbenes into a benzene ring is observed in the thermolysis of 226 (equation 139)134. 

For example, reaction of ethyl diazopyruvate with cyclohexene in the presence of rhodium 126) or copper113 126 catalysts furnishes, besides the 7-exo-substituted norcarane 108, a small amount of 110, which may arise either from allylic insertion or from the 7-mfo-substituted norcarane 109 by a thermal 1,5-homo-hydrogen shift. 

Examples are known where intermolecular carbenoid transformations between diazomalonates or certain diazoketones and appropriate olefins result in competition between formation of cyclopropane and products derived from allylic C—H insertion2-4. For example, catalytic decomposition of ethyl diazopyruvate in the presence of cyclohexene gave the 7-ejco-substituted norcarane 93 together with a small amount of the allylic C—H insertion product 94 (equation 95)142 143. In some cases, e.g. rhodium(II) decomposition of a-diazo-j8-ketoester 95, the major pathway afforded C—H insertion products 96 and 97 with only a small amount of the cyclopropane derivative 98. In contrast, however, when a copper catalyst was employed for this carbenoid transformation, cyclopropane 98 was the dominant product (equation 96)144. The choice of the rhodium(II) catalyst s ligand can also markedly influence the chemoselectivity between cyclopropanation and C—H... 

Extensive investigations by Liu confirmed a first-order reaction of thermal decomposition of chlorodiazirines as well as formation of typical stabilization products of carbenes. Thus tetrachloroethylene was formed from trichloromethylchlorodiazirine 178 norcaranes were obtained on decomposition of arylchlorodiazirines in cyclohexene from cyclooctylchloro-... 

N.m.r. chemical shifts of a number of monoterpenoids of this class are included in a study of bicyclo[4,l,0]heptanes. A further paper in a series on enthalpies of combustion and formation concerns the 3,4-epoxycaranes. (+)-Car-2-ene and (—)-car-2-ene of high optical purity have been synthesized from the respective (-)- and (+)-rran5-caran-2-ones, via the analogous and uncited tosylhydrazone/methyl-lithium route used by Cocker et al. for synthesizing (—)-cw-car-4-ene (Vol. 1, p. 47), thus providing access (Vol. 2, p. 29, ref. 108) from the readily available (+)- and (-)-dihydrocarvones. Cocker et al. have synthesized norcaran-3-one via dibromocarbene addition to 4,4-dimethoxy-cyclohexene and treatment with lithium dimethylcuprate) from which car-2-ene, car-3-ene, and car-3(10)-ene were prepared. ... 

The results obtained from the irradiation at 235 nm of vibrationally excited dichloromethane suggest that there is higher non-adiabaticity for vibrationally excited molecules.Laser irradiation at 355 nm of methylene chloride and methylene bromide brings about ionization.A simple C-Br bond fission is the key step in the photodissociation of methylene dibromide at 248 nm. Ionization of methylene bromide in the 10-24 eV range has been reported. Irradiation of methylene iodide in water has provided evidence for the formation of iodine atoms and protons.Further work on the photochemical behaviour of methylene iodide has reported that vibrationally relaxed CH2l- T reacts with cyclohexene to afford norcarane. ... 

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