Peroxides Cyclopropanes, reaction with

One such agent is prepared by NBS and peroxide bromination of ethyl 4-chiorophenylacetate (108) to give 109. This is converted by sodium hydride to the benzylic carbene, which is inserted into the double bond of ethyl acrylate to give cis-cyclopropane 110. Partial saponification cleaves the less hindered ester moiety to give 111. This is next converted to the alkoxyimide (112) on reaction with diethyl carbonate and diammonium phosphate. Stronger base (NaOEt)... 

A cis addition mechanism is generally accepted for the reaction, because cis addition to an olefinic bond generally occurs with predominant attack at trans bonds, and the Simmons-Smith reagent attacks preferentially one of the trans olefinic bonds of trans,trans,cis-1,5,9-cyclodode-catriene and then the cis double bond of the monoadduct (378). The close correspondence in relative rates of olefins for the cyclopropane formation by the Simmons-Smith reaction with those for diimide reduction and peroxide epoxidation supports the concept 409). The latter two reactions are generally considered to proceed via cis addition. 

In a detailed investigation of the mechanism and scope of palladium catalyzed amination of five-membered heterocycles, the 1-methyl-3-bromoindole 145 was aminated with secondary amines to the 3-aminoindoles 146. Similar results were obtained for l-methyl-2-bromoindole <03JOC2861>. Rhodium-catalyzed cyclopropanation reactions involving 1-methyl-3-diazooxindole and exocyclic alkenes provided novel dispirocyclic cyclopropanes <03SL1599>. New applications of palladium-mediated cross-coupling reactions have been utilized to prepare a variety of functionalized indoles. Suzuki-Miyaura coupling reactions of indole-3-boronates <03H(59)473> and indole-5-boronates <03H(60)865> were utilized to prepare inhibitors of lipid peroxidation and melatonin analogues, respectively. 

Hydroboration of an allylic chloride gave a cyclopropane 14 when the intermediate or-ganoborane was treated with aqueous sodium hydroxide. 9-Borabicyclo[3.3.1]nonane is particularly suitable the geometry present in the alkene is retained in the product. 3-Bromopropyne underwent reaction with two equivalents of 9-borabicyclo[3.3.1]nonane, subsequent treatment with methyllithium and then with hydrogen peroxide gave cyclopropanol. 

Reaction of the cyclopropane 15 with methanol followed by alkaline hydrogen peroxide gave the cyclopropanol 16 (89%), whereas heating in caproic acid led to 1-allyl-l-methylcycloprop-ane (86%)."°... 

In a similar reaction with dibenzotricyclo[3.3.0.0 ]octadiene (12), methanol was added across the cyclopropane bond that linked both benzylic carbon atoms upon irradiation in methanol. Similarly, trichloromethyl bromide was added when benzoyl peroxide was used as a radical initiator, ... 

R=COgMe). Some evidence is presented for the initial oxidation of Cu to Cu by peroxide impurities in the olefin and this functions as the active catalyst. Cyclopropanation of olefins by reaction with ZnEtg-CHBrs mixtures in the presence of oxygen probably proceeds via a radical pathway in view of the observed rate inhibition by styrene. The bromocarbenoid intermediate generated (BrgHCZnR R=H or Et) shows high jy -selectivity for the addition to cyclo-octene and cw-but-2-ene. 

The unusual ring-opening reaction of the cyclopropane (191) with a sulphone anion leads to the vinylsilane (192) (Scheme 15). Conversion of (192) into the ketone (193), followed by fluoride-induced cyclization, then gives a cyclopentane (194). However, conversion of (192) into the aldehyde (195), followed by treatment with alkaline hydrogen peroxide, afforded an epoxy-ketone, presumably via the enone (196). ... 

Chlorination or bromination of olefins in presence of hydrogen peroxide result in formation of /Mialoperoxides423,424 and a similar reaction takes place with cyclopropane derivatives425. Pyrazole also reacts under these conditions426. 

Bennett and coworkers (138) have prepared the acetyl radical CH CO by the reaction between Na and acetyl chloride and have obtained an isotropic value of 5.1 gauss for the proton splitting. An ESR spectrum attributed to CH CO with 16 gauss was earlier reported during photolysis of biacetyl (276) in a solid matrix. Recently a series of benzoyl 6-radicals (277) have been observed in the liquid photolysis of the corresponding benzaldehyde in a cyclopropane solution containing di-t-butyl peroxide. For the first time, it is possible to study in these radicals the delocalization of the unpaired electron from the acyl 6-system into the adjacent phenyl ir-system. The significant conclusion from this study is the... 

In so far as the rate of formation of radicals reflects their stability or reactivity the findings of Hart and Wyman are instructive. In carbon tetrachloride the rate of decomposition of benzoyl peroxide was twice as fast as that of biscyclopropanoyl peroxide. Ingold and coworkers have found that in the photodecomposition of benzoyl and biscyclopropanoyl peroxides, in carbon tetrachloride at 298 K, the phenyl radicals produced reacted faster (7.8 x 10 M s ) than the cyclopropyl radicals (1.5 X 10 M s ). These results are consistent with C-H bond dissociation energies for benzene (llOkcalmol) and cyclopropane (106kcal mol ) which implies that the cyclopropyl radical should be less reactive than the phenyl radical. In subsequent work they also showed that at ambient temperatures radical reactivities decreased along the series /c = Ph > (Me)2 C=CH > cyclopropyl > Me. Table 4 records the absolute rate constants for the reaction of these radicals with tri-n-butylgermane. 

Cleavage of cyclopropanes. In the absence of a solvent, cyclopropanes are reductively cleaved by diborane. Thus norcarane heated with diborane at 100 for 1-2 hrs. gives the alkylborane (2), identified by peroxide cleavage to cyclohexyl-methanol (3). No reaction occurred in tetrahydrofurane. 

The apparent activation energy for the y-ray induced formation of carbonyl difluoride is calculated to be 18.0 kj moP . The kinetics results indicate a chain mechanism in which primary radicals formed from the irradiation of CjF, induce its copolymerization with Oj-The resulting long-chain peroxide radicals decompose by splitting off COFj or CjF O, depending upon whether a carbon-carbon, or oxygen-oxygen bond is broken. The perfluorinated cyclopropane is considered to be formed independently, in a minor side-reaction [420]. 

Bis(diphenylphosphino)cyclopropane (1), the first reported ge j-diphosphinocyclopropane, is oxidized by hydrogen peroxide in aqueous tetrahydrofuran to afford l,l-bis(diphenylphos-phinoyl)cyclopropane (6)." The reaction of 1 with sulfur in tetrahydrofuran yields l,l-bis(di-phenylphosphinothioyl)cyclopropane (7). ... 

Treatment of various cyclopropyl derivatives of the endoperoxide of 2,3-dioxabicyclo[2.2.2]oct-5-ene with triethylamine in dichloromethane resulted in an intramolecular redox reaction involving the peroxide moiety to give cyclopropyl hydroxyalkyl ketones. The yields were good dispiro[cyclopropane-l,5 -[2,3]dioxabicyclo[2.2.2]oct-7-ene-6, l"-cyclo-propane] (13) gave 10-hydroxydispiro[2.0.2.4]dec-8-en-7-one (14) in 80 /o yield. Treatment of similar unsaturated endoperoxides with alumina gave diketones, whereas thermolysis and photolysis of 13, like other unsaturated endoperoxides, afforded an mixture of an... 

The reaction of bicyclo[4.1.0]heptane with diborane and subsequent treatment with hydrogen peroxide produced predominantly cyclohexylmethanol (5b) in high yield.Under modified experimental conditions small amounts of isomeric methylcyclohexanol (6b) and cycloheptanol (7b) were isolated. In contrast to the hydroboration of alkenes, the cyclopropane cleavage reaction is inhibited by ethereal solvents such as diethyl ether, tetrahydrofuran or 2-methoxy-ethyl ether. Bicyclo[3.1.0]hexane reacted with diborane in a similar fashion to give mainly cyclopentylmethanol (5a).The reaction of l-methylbicyclo[4.1.0]heptane gave a mixture of cis- and tram-(2-methylcyclohexyl)methanol (5c) in an initial ratio of 60 40. Spiro[2.5]octane reacted with diborane to yield only products derived from scission at the spiro carbon. The main product was 2-cyclohexylethanol (8). ... 

Table 12. Homoallylic Alcohols and 1,4-Diols by Reaction of (Silylmethyl)cyclopropanes with Haloboranes and Hydrogen Peroxide"...

Benzocyclopropene reacts with a variety of radical reagents (for example A -bromosuccinimide carbon tetrachloride bromotrichloromethane bromoform/benzoyl peroxide alkyl sulfide and ethane-1,2-dithiol with photolysis) to afford products derived from cleavage of the cyclopropane ring. The preferential mode of reaction consists of a chain reaction initiated by radical addition at Cl a followed by opening of the cyclopropyl radical to afford a benzyl radical. Yields are generally low except for the addition of the alkylsulfanyl radical, e.g. formation of 1, and no products derived from addition to the central tt-bond are formed. Cyclopropa[A]naphthalene reacts similarly with radicals and gives 2-methylnapthalene derivatives, while no addition to the central 7i-bond is observed. ... 

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