O-Methylacetophenone

Indeed, it turned out to be possible to model the observed behavior with the simple Bell-model, which implies tunneUng through a parabolic barrier of height and width b [16]. Fitting the lines for the protio- and the deutero-derivatives to the observed points yielded = 16 kj mol and b = 1.44 A, both of which are reasonable values, although they are associated with a considerable uncertainty. 

This process was suppressed when the methyl groups were deuterated after X-irradiation no bands of the enol radical cation were seen however, only a 

Thus we faced an interesting set of results (i) enolization in methylindanone radical cations can be induced by irradiation at 490 nm, where the ketone radical cation absorbs re-ketonization can be induced by irradiation in the red, where only the enol radical cation absorbs, (ii) In 6(h ) enolization occurs slowly at 12 K, whereas in 7(h3) + it occurs apparently so rapidly that the ketone radical cation can never be observed, even after photolysis at 490 nm. (iii) 7(dj) behaves similarly to 7(hg) on ionization, a mixture of ketone and enol radical cation is formed, and the ketone radical cation can be re-formed (and observed) after photolysis in the red. 

According to calculations, the ground state of the parent 1-indanone radical cation is of the a-radical nature, while in its 7-methyl derivative, that state is nearly degenerate with the lowest 3t-radical state. In the 4,7-dimethyl derivative that %-radical state falls about 0.4 eV below the a-radical state, a fact which expresses itself also in a clearly separated low-energy band in the photoelectron spectrum of 6 [17]. Thus, in order to effect a H-atom transfer, the radical cation of 6 must first climb to the higher-lying a-radical state, before it can access the potential surface that leads adiabatically to the H2C-twisted enol radical cation. 

Actually, new DFT calculations carried out by the author of this chapter show that the distance factor which we had set out to explore at the time, by comparing the reactivity of tetralone S and indanone 6 is less important than we thought. The activation energy for enolization of 3 + is only about 1.5 kcal mol lower than that for 6, so the tunneling rates in the two compounds would be quite similar. It would be interesting to explore this with methods of time-resolved spectroscopy. 

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Di-/ -butyl phthalate 4-Methylacetanilide, p-Toluidine Methyl acetate, see Methvl tert-butvl ether Methylacetoacetate, see Mevinphos o-Methylacetophenone, see o-Xylene /n-Methylacetophenone, see ro-Xylene p-Methylacetophenone, see p-Xylene... 

A higher enantioselectivity is obtained at a lower temperature. The enantioselectivity by 31b/(5,5)-DPEN is higher than that by ( )-10b/(5,5)-DPEN at the same temperature and pressure. The tropos 31b/(5,5)-DPEN catalyst affords (f )-l-(l-naphthyl) ethanol with 92% ee in quantitative yield (entries 3 and 4). 31b/(5,5)-DPEN is also effective for o-methylacetophenone 22a to afford (7 )-l-(l-o-methylphenyl)ethanol quantitatively with 88% ee, higher than 86% ee obtained by ( )-10b/(5,5)-DPEN (entries 5 and 6). 

Photolysis of oe-chloro-o-methylacetophenones yields 1-indanones. The mechanism has been studied by laser flash photolysis (Netto-Ferreira, J. C. Scaiano, J. C., J. Am. Chem. Soc., 1991, 113, 5800). Develop a Dauben-Salem-Turro state correlation diagram for the photochemical step and, on the basis of your diagram, discuss the efficiency of the reaction on the singlet and triplet manifold. Do the experimental results agree with your analysis ... 

Chloromethoxycarbene ( CC10CH3), 115 a-Chloro-o-methylacetophenone, 300 m-Chloroperbenzoic acid epoxidation by, 102 JV-Chloropyridine, 287 interaction diagram, 287 SHMO, 287... 

When a mixture of powdered ketone and NaBH4 is kept at room temperature, reduction of the ketone occurs to give the corresponding alcohol [2], When the reaction is carried out in inclusion crystals containing a chiral host compound, the optically active alcohol can be obtained by enantio-control of the reaction by the chiral host. For example, treatment of inclusion crystals of acetophenone (2a) or o-methylacetophenone (2b) and (S,S)-(-)-1,6-bis(o-chlorophenyl)-1,6-diphenylhexa-2,4-diyne-l,6-diol (1) [3] with powdered BH3-ethylenediamine complex (3) in the solid state gave 4a of 44 % ee (96 % yield) or 4b of 59 % ee (57 % yield), respectively [4],... 

When the cyclic enone is hydrogenated with the racemic Tol-BINAP/Ru(II) complex and (5, 5)-DPEN under otherwise identical conditions, the 5 allylic alcohol is obtained in 95% ee and 100% yield. The ee value is close to the 96% attained with the enantiomerically pure (f )-TolBINAP/ 5, 5)-DPEN system. Hydrogenation of o-methylacetophenone catalyzed by RuCl2[( )-tolbinap](dmf) and (5,5)-DPEN results in the R alcohol in 90% ee and 100% yield (eq 6). The S/S,S catalyst gives the R product in 97.5% ee. 

The Ti species abstracts hydrogen from the alcohol (p. 347), and then dimerizes. The /PrO radical, which is formed by this process, donates H to another molecule of ground-state benzophenone, producing acetone and another molecule of 51. This mechanism predicts that the quantum yield for the disappearance of benzophenone should be 2, since each quantum of light results in the conversion of 2 equivalents of benzophenone to 51. Under favorable experimental conditions, the observed quantum yield does approach 2. Benzophenone abstracts hydrogen with very high efficiency. Other aromatic ketones are dimerized with lower quantum yields, and some (e.g., p-aminobenzophenone, o-methylacetophenone) cannot be dimerized at all in 2-propanol (although p-aminobenzophenone, e.g., can be dimerized in cyclohexane ). The reaction has also been carried out electrochemically. 

A formal [1,5] hydrogen shift occurs in photoenolization of compounds such as o-methylacetophenone (110). The reaction proceeds in the triplet state by way of hydrogen abstraction and involves biradical intermediates and an equilibrium of the triplet states of Z- and -enol (Haag et al., 1977 Das et al., 1979). 

Further increase in enantioselectivity was attained at a lower reaction temperature (Run 3). The enantioselectivity by the RuCl2(dmbiphep) (4b)/(5,5)-dpen was higher than that by the ( )-RuCl2(dmbinap) (3b)/(S,5)-dpen complex at the same low temperature and high pressure (Run 4). Thus, (R)-l-(l-naphthyl)ethanol was obtained with 92% ee in quantitative yield. RuCl2(dmbiphep) (4b)/(5,S)-dpen was also useful in the reduction of o-methylacetophenone. 

Chloromethoxycarbene (tCClOCHs), 115 u-Chloro-o-methylacetophenone, 300 m-Chloroperbenzoic acid... 

Investigation of the temperature dependence of the photochemistry of o-methylacetophenone has revealed that the rate of decay of the biradical generated in the photoenolization is associated with a low A factor. An explanation for the effect lies in the requirement for spin inversion in the process. The key step in a newly developed synthesis of ( )-oestrone is the photoinduced cyclization (1) (2). Excitation of (1) induces photoenolization to the kinetically... 

Larger deviations from semi-classical behaviour have been observed in the reaction of o-methylacetophenone and p-methoxyacetophenone with hydroxide ions, in which the protium compound was studied by bromination and the tritium compound by detritiation. For these two reactions E -E had values of 3.6 0.4 and 3.3 0.9 kcal mol" respectively, compared with the expected value of 1.7 kcal mol" while the values of lg(/4XM ) were 1.5 0.3 and 1.1 0.6. Although the precision of these last values is not high, they certainly lie outside the semi-classical limits. ... 

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