Ketones phenyl, cleavage

The first application of the time-resolved CIDNP method by Closs and co-workers involved tire Norrish 1 cleavage of benzyl phenyl ketone [24, 25]. Geminate RPs may recombine to regenerate the starting material while escaped RPs may fonn the starting ketone (12), bibenzyl (3), or benzil (4), as shown below. 

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). 

Chloro-7-(2-fluorophenyl)-5/f-dibenz[c,e]azepine (54) has been prepared in a similar manner from 2-[2-(bromomethyl)phenyl)-5-chloro-2 -fluorodiphenyl ketone (53, X = Br),93 but can be obtained in a superior yield (85%) as the methanesulfonate salt by cleavage of the [(dimethylamino)methyl] derivative 53 (X = NMe2) with cyanogen bromide followed by treatment with ethanolic ammonia.94... 

Ketones are oxidatively cleaved by Cr(VI) or Mn(VII) reagents. The reaction is sometimes of utility in the synthesis of difunctional molecules by ring cleavage. The mechanism for both reagents is believed to involve an enol intermediate.206 A study involving both kinetic data and quantitative product studies has permitted a fairly complete description of the Cr(VI) oxidation of benzyl phenyl ketone.207 The products include both oxidative-cleavage products and benzil, 7, which results from oxidation a to the carbonyl. In addition, the dimeric product 8, which is suggestive of radical intermediates, is formed under some conditions. 

Type I cleavage of ketones, 75 Type II cleavage of ketones effect of 7-substituents, 122-124 effect of ring substituents, 124 of 5 -(+)-4-methyl-l-phenyl-1- hexanone, 118... 

Frequently B will also undergo a back hydrogen transfer which regenerates the parent ketone, as well as cyclization (in most cases a minor reaction) as a result of this competition the quantum yields of fragmentation are typically in the 0.1-0.5 range in non-polar media. When the Norrish Type II process takes place in a polymer it can result in the cleavage of the polymer backbone. Poly(phenyl vinyl ketone) has frequently been used as a model polymer in which this reaction is resonsible for its photodegradation, reaction 2. 

The a-cleavage in molecular ions of ketones, amines, ethers and similar functionalized compounds yields specific cleavage products of high importance for structure elucidation. Analogous behavior is observed in the mass spectra of phenylal-kanes. [49]... 

Cleavage of a benzylic carbon-carbon bond is observed from aromatic radical-cations in cases where the resulting fragments are stabilised by substituents. Bond cleavage occurs, for example, with dialkylphenylcarbinols involving loss of the more stable alkyl radical and leaving a phenyl alkyl ketone [85, 86],... 

Halogenation Reactions. Chlorination of 4-acyl-2-phenyl-5(4f/)-oxazolones 213 with sulfuryl chloride leads to the corresponding 4-chloro derivatives 214 (Scheme 7.66). These compounds are useful intermediates in organic synthesis. In particular, hydrolytic cleavage of 214 affords a-chloro-a-acylamino ketones... 

---