Phenyl-carbon bond

The sulfur ylid Me2S(0)CH2 is a very weak base, and, when coordinated to nickel in the complex [Ni( / -C2H4)2CH2S(0)Me2] (91), spontaneous decomposition to ethane, cyclopropane, and methane occurs (93). In another reaction, compound 92 rearranges under UV irradiation to yield, with insertion of iron into a phenyl-carbon bond, a cyclic carbene complex, 93 94). 

The MSP sample cured at 150°C shows two new peaks at 131.8 ppm and 144 ppm. The peaks come from the carbons without directly-bonded protons. Although there is no change in the intensity of the peak at 131.8 ppm, that at 144 ppm increases in intensity and is broadened with an increase in curing temperature. The peak at 131.8 ppm corresponds to the 4a and 8a position carbons of the naphthalene ring and that at 144 ppm corresponds to the C=C carbons and the phenyl carbons bonded to the C=C bond, and the biphenyl bonds carbons. 

The most thoroughly studied of the phenoxy acids is 2,4-D. Its photochemical decomposition by hydrolysis and oxidation leads, through various intermediate products, to chlorine-free polyquinoidal humic adds. The cleavage of the phenyl— carbon bond, leading to the 2,4-dichlorbphenol intermediate, is sensitised by riboflavin. 1,2,4-Trihydroxybenzene formed by hydroxy substitution is oxidised by air to 2-hydroxybenzoquinone, which is then polymerised (Crosby and Tutass,... 

Iwasawa et al. [21] also reported chelation-assisted reactions in an article entitled Rhodium(I)-Catalyzed Direct Carboxylation of Arenes with CO2 via Chelation-Assisted C-H Bond Activation, in which the cyclometalation reactions proceed easily and form cyclometalation intermediates. The metal atoms are active centers in their intermediates. Hence, the active metal atom reacts easily with inert carbon dioxide to give carboxylic acid derivatives. Examples include the cyclometalation of 2-phenylpyridine as a substrate in the presence of a rhodium intermediate. Carbon dioxide can be inserted into the rhodium-phenyl carbon bond, and a methyl ester is formed with TMSCH2N2 from a rhodium carboxylate, as shown in Eq. (6.5). The reaction mechanism is proposed as shown in Scheme 6.2 [21]. 

Since the phenyl group is linked, in both reactants and products, to a saturated carbon atom, the intervening bonds are localized and should have similar bond energies. The heats of reaction should therefore be the same in both cases. However, the central carbon atom in the transition state has sp hybridization and forms part of a delocalized allyl-like structure. The transition state in equation (5.100) is therefore stabilized both by the change in phenyl-carbon bond type (to sp -sp ) and by the conjugative interaction between phenyl and the delocalized system in the transition state. Therefore benzyl chloride reacts faster with iodide ion than does a simple primary alkyl chloride, although the heats of reaction are similar. 

Diphenylthiirene 1-oxide reacts with hydroxylamine to give the oxime of benzyl phenyl ketone (79JA390). The reaction probably occurs by addition to the carbon-carbon double bond followed by loss of sulfur monoxide (Scheme 80). Dimethylamine adds to the double bond of 2,3-diphenylthiirene 1,1-dioxide with loss of sulfur dioxide (Scheme 81) (75JOC3189). Azide ion gives seven products, one of which involves cleavage of the carbon-carbon bond of an intermediate cycloadduct (Scheme 81) (80JOC2604). 

There is no clear reason to prefer either of these mechanisms, since stereochemical and kinetic data are lacking. Solvent effects also give no suggestion about the problem. It is possible that the carbon-carbon bond is weakened by an increasing number of phenyl substituents, resulting in more carbon-carbon bond cleavage products, as is indeed found experimentally. All these reductive reactions of thiirane dioxides with metal hydrides are accompanied by the formation of the corresponding alkenes via the usual elimination of sulfur dioxide. 

The rates of radical-forming thermal decomposition of four families of free radical initiators can be predicted from a sum of transition state and reactant state effects. The four families of initiators are trarw-symmetric bisalkyl diazenes,trans-phenyl, alkyl diazenes, peresters and hydrocarbons (carbon-carbon bond homolysis). Transition state effects are calculated by the HMD pi- delocalization energies of the alkyl radicals formed in the reactions. Reactant state effects are estimated from standard steric parameters. For each family of initiators, linear energy relationships have been created for calculating the rates at which members of the family decompose at given temperatures. These numerical relationships should be useful for predicting rates of decomposition for potential new initiators for the free radical polymerization of vinyl monomers under extraordinary conditions. 

The phosphonium salt (116) gave the phosphorane (117) with phenyl-lithium although it has hydrogen atoms attached to carbon bonded to phosphorus. ... 

It is supposed that the nickel enolate intermediate 157 reacts with electrophiles rather than with protons. The successful use of trimethylsilyl-sub-stituted amines (Scheme 57) permits a new carbon-carbon bond to be formed between 157 and electrophiles such as benzaldehyde and ethyl acrylate. The adduct 158 is obtained stereoselectively only by mixing nickel tetracarbonyl, the gem-dibromocyclopropane 150, dimethyl (trimethylsilyl) amine, and an electrophile [82]. gem-Functionalization on a cyclopropane ring carbon atom is attained in this four-component coupling reaction. Phenyl trimethyl silylsulfide serves as an excellent nucleophile to yield the thiol ester, which is in sharp contrast to the formation of a complicated product mixture starting from thiols instead of the silylsulfide [81]. (Scheme 58)... 

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