Carbon tetrachloride, radical addition reactions

Fluorinated adducts can be obtained either by addition of polyfluoroalkyl halides to various alkenes or by condensation of halides, such as bromotrichloromethane or carbon tetrachloride, with fluorinated alkenes. Factors which control the regiospecificity and relative rate of these free-radical addition reactions have been studied. 

The present method offers several advantages over earlier methods. The use of carbon tetrachloride instead of diethyl ether as solvent avoids the intrusion of certain radical-chain reactions with solvent which are observed with bromine and to a lesser degree with chlorine. In addition, the potassium bromide has a reduced solubility in carbon tetrachloride compared to diethyl ether, thus providing additional driving force for the reaction and ease of purification of product. The selection of bro-... 

One of the older preparative free-radical reactions is the addition of polyhalomethanes to alkenes. Examples of addition of carbon tetrabromide, carbon tetrachloride, and bromoform have been recorded. The reactions are chain processes that depend on facile abstraction of halogen or hydrogen from the halomethane ... 

Allenylcobaloximes, e.g. 26, react with bromotrichloromethane, carbon tetrachloride, trichloroacetonitrile, methyl trichloroacetate and bromoform to afford functionalized terminal alkynes in synthetically useful yields (Scheme 11.10). The nature of the products formed in this transformation points to a y-specific attack of polyhaloethyl radicals to the allenyl group, with either a concerted or a stepwise formation of coba-loxime(II) 27 and the substituted alkyne [62, 63]. Cobalt(II) radical 27 abstracts a bromine atom (from BrCCl3) or a chlorine atom (e.g. from C13CCN), which leads to a regeneration of the chain-carrying radical. It is worth mentioning that the reverse reaction, i.e. the addition of alkyl radicals to stannylmethyl-substituted alkynes, has been applied in the synthesis of, e.g., allenyl-substituted thymidine derivatives [64],... 

As an alternative to radical chlorination, use has been made of carbon tetrachloride and hexachloroethane in the presence of a quaternary ammonium salt, as source of the chloronium ion for reaction with activated alkylbenzenes [38], Benzyl chlorides need the additional activation of a nitro group for their conversion into the corresponding nitrobenzotrichlorides, whereas benzal chlorides do not need the extra activation for a similar conversion. The same synthetic protocol, using hexachloroethane, has been used for the conversion of allylic sulphones into the 1,1-dichloro derivatives [39],... 

Irradiation of diazo 21d in carbon tetrachloride gave, in addition to 72 (R = Me) and 73, the 3-chloro-3-trichloromethyl-l-methyloxindole (76a) (64JOC3577). Since the photolysis in carbon tetrachloride under comparable conditions produces, in the primary step, CCI3 radicals and chlorine atoms (63JOC3442), in the formation of 76a and probably in the reaction with oxygen to give 74, the carbene 71 shows biradical properties in the... 

Another application of ruthenium indenylidene complexes was the atom transfer radical addition of carbon tetrachloride to vinyl monomers reported by Verpoort [61]. This Kharasch reaction afforded good yields for all substrates tested, especially with the catalyst VIII (Equation 8.11, Table 8.8). 

Homolytic cleavage of covalent bonds is an alternative means of generating free radicals. This may be assisted by the addition of an electron as in the case of carbon tetrachloride activation. The electron may be donated by cytochrome P-450, allowing the loss of chloride ion and the production of a trichloromethyl radical (Fig. 4.7). This can initiate other radical reactions by reacting with oxygen or unsaturated lipids. 

Styrene is a colorless liquid with an aromatic odor. Important physical properties of styrene are shown in Table 1. Styrene is infinitely soluble in acetone, carbon tetrachloride, benzene, ether, -heptane, and ethanol. Polymerization generally takes place by free-radical reactions initiated thermally or catalytically. Styrene undergoes many reactions of an nnsaturated compound, such as addition, and of an aromatic compound, such as substitution. 

The reactions of cyclic disilenes with haloalkanes proceed in a similar way. Cyclotrisilene 48 reacts with carbon tetrachloride without cleavage of endocyclic Si-Si bonds to give trans-1,2-dichlorocyclotrisilane 179 stereo specifically [Eq. (84)].24 The a h -stereochemistry is in good accord with the radical mechanism of the reactions as stated above. Similarly, cyclic disilenes 49 and 50 react with carbon tetrachloride and 1,2-dibromoethane giving the corresponding trau.v-1,2-dihalodi-silanes 180 [Eq. (85)].129 Methyl iodide adds to cyclic disilene 50 in an a tz-addition manner to give 181.104... 

Susuki and Tsuji reported the first Kharasch addition/carbonylation sequences to synthesize halogenated acid chlorides from olefins, carbon tetrachloride, and carbon monoxide catalyzed by [CpFe(CO)2]2 [101]. Its activity is comparable to or better than that of the corresponding molybdenum complex (see Part 1, Sect. 7). Davis and coworkers determined later that the reaction does not involve homolysis of the dimer to a metal-centered radical, which reduces the organic halide, but that radical generation occurs from the dimeric catalyst after initial dissociation of a CO ligand and subsequent SET [102]. The reaction proceeds otherwise as a typical metal-catalyzed atom transfer process (cf. Part 1, Fig. 37, Part 2, Fig. 7). 

Copper(I) salts have been found to be particularly good catalysts for radical addition of alkyl halides to alkenes689. These catalysts have been used in the reaction of carbon tetrachloride with ester-containing alkenes, the products being key intermediates in the synthesis of -lactams (equation 108). 

Dowbenko (1964) has shown that carbon tetrachloride, chloroform and several other compounds react with a s-cis-l,5-cyclo-octadiene by a free-radical transannular 1,5-cyclo-addition to give derivatives of bicyclo-[3,3,0]octane. He suggested that the cyclo-addition may occur by a concerted reaction in which the configuration of the diene is such that the two double bonds lie in close proximity, or alternatively by a step-wise reaction which involves a free-radical addition across the ring. 

In 1967, Heiba and Dessau reported perhaps one of the earliest examples of a radical cychzation cascade that is initiated by intermolecular addition of C-centered radicals to alkynes. Reaction of carbon tetrachloride with 1-heptynes 1 in the presence of benzoyl peroxide (BPO) as radical initiator resulted, among other products, in the formation of 1,1-dichlorovinylcyclopentane derivatives 2 in moderate yields (Scheme 2.1). °... 

For example, the addition of carbon tetrachloride to 1-octene yields 1,1,1,3-tetrachlorononane (85%). The reactions are carried out under pressure in the usual hydrogenation equipment when low-boiling reactants are involved. When this free-radical-initiated reaction is applied to a combination of ethylene and a polyhalomethane, products of the general formula X(CHjCHj),jY are obtained, in which X is hydrogen or halogen and Y is the remainder of the polyhalomethane molecule. ... 

The chemistry of 149 is rather unusual from the point of view of the typical reactivity pattern observed for ordinary small-ring systems. Especially striking is the ease of central bond opening in radical reactions. Thus 149 spontaneously reacts with iodine, thiophenol, and even with carbon tetrachloride to give almost quantitative yields of the respective 1,3-adducts 153a-c (Scheme 4.51). A number of other additions, including those leading to the formation... 

Interesting possibilities for the synthesis of new types of polysaccharide derivatives are offered by the reaction of addition to double bonds, which proceeds by a free-radical mechanism. The presence of initiators of free-radical polymerization (benzoyl peroxide, tert-butyl peroxide, dicumyl peroxide, dinitrile of azodiisobutyric acid), also irradiation with ultraviolet light, has effected the addition to 5,6-cellulosene of chloroform, carbon tetrachloride, methylmonochloroacetate, dimethyl-phosphite and other compounds that decompc under the conditions of a reaction with the formation of free radicals (45,46). The reaction proceeds as follows ... 

The radical reaction of carbon tetrachloride with aliphatic double bonds involves addition of the trichloromethyl radical to the double bond, followed by chlorine atom abstraction from carbon tetrachloride by the intermediate radical to give the product. After the addition of the trichloromethyl radical to /3-pinene, a fragmentation occurs prior to formation of the product. 

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