Of cyclohexene with methylene iodide

Norcarane has been prepared by the reduction of 7,7-dichlo-ronorcarane with sodium and alcohol,6 and by the light-catalyzed reaction of diazomethane with cyclohexene.6 The reaction of cyclohexene with methylene iodide and zinc-copper couple represents the most convenient preparation of norcarane which is of high purity. 

Cyclopropanation of olefins (1, 253 2, 134). Cyclopropanation of olefins with the diethylzinc-methylene iodide reagent is markedly accelerated by oxygen. In addition yields are improved. Thus the reaction of cyclohexene with the carbcnoid in the presence of air is complete within 30 min. norcarane is obtained in 90 % yield. The yield is 53 % when the reaction is carried out under nitrogen.1... 

A dry flask is charged with methylene iodide (190g, 0.71 mol), zinc-copper eouple (46.8 g, 0.72 g atom), cyclohexene (53.3 g, 0.65 mol), diethyl ether (250 mL) and a crystal of iodine. The mixture is heated under reflux for 15 h. The decanted ether solution is worked up in the usual way and the crude product purified by distillation affording norcarane (36 g, 58% bp 116-117 °C). ... 

Cyclohexene, purification of, 41, 74 reaction with zinc-copper couple and methylene iodide, 41, 73 2-CyclohEXENONE, 40,14 Cydohexylamine, reaction with ethyl formate, 41, 14... 

Melhylenecydobutane-l,2-dicar-boxylic anhydride, 43,27 Methylenecydobutanes by addition of allenes to alkenes, 43, 30 Methylenecyclohexane, 40, 66 Methylene iodide, reaction with zinc-copper couple and cyclohexene, 41, 73... 

A highly convenient and versatile cyclopropanation method has been devised which involves treatment of olefins with different organoaluminum compounds and alkylidene iodide under mild conditions [93]. Although Miller found that cyclopropane formation by use of EtsAl-methylene iodide in cyclohexene proceeds in quite disappointing yields [94], Yamamoto and Maruoka reached the conclusion that the intermediate dialkyl(iodomethyl)aluminum species 97 is responsible for the cyclopropanation of olefins and that it readily decomposes in the absence of olefins or in the presence of excess trialkylaluminum. Hence the use of equimolar amounts of trialkyl-aluminum and methylene iodide in the presence of olefins is essential for the achievement of reproducible results in the cyclopropanation process. In addition, because di-alkylaluminum halide can also be used as a cyclopropanation agent, the use of half an equivalent of trialkylaluminum is not detrimental (Sch. 61). 

Nature of the reagent. The du Pont chemists who discovered the reagent later defined precise directions for its generation and use in reaction with cyclohexene to form norcarane. The reagent is generated by reaction of methylene iodide in... 

With these possibilities in mind we attempted the photo-oxygenation of norbornene. With either methylene blue or hematoporphyrin as sensitizer and methanol or pyridine as solvent, we obtained no evidence of any reaction by infrared or NMR spectrum, by gas chromatography, or by spot test for hydroperoxide (potassium iodide/starch in 2-propanol/ acetic acid) or peroxide (hydriodic acid/starch in 2-propanol). While the half-life of reaction of cyclohexene was only about one day under our reaction conditions, no evidence of reaction of norbornene was obtained in a period of one month. Assay of norbornene by gas chromatography with benzene as internal standard failed to show any depletion of norbornene over the attempted reaction interval. 

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 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. ... 

Zinc and Mercury.—As in previous years, reports of new transformations and methodologies involving zinc have been at a low level. A useful high-yielding conversion has been published, however, of allylic thioethers such as (84) into homoallylic thioethers (85). The initial ylide formation with a homogeneous solution of diethylzinc and methylene (R = H) or ethylidene (R = Me) iodide is followed by a 2,3-sigmatropic rearran ment to the observed products, and the poor yields found in previous experiments can be avoided by quenching the reaction mixture with acetaldehyde. Conventional Simmons-Smith cyclo-propanation of these compounds fails, as does the cyclopropanation of cyclohexene in the presence of various thioethers. 

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