2.4.5- Trimethylacetophenone

Trimethylacetic acid may be made by the hydrolysis of tert-butyl cyanide with weak hydrochloric acid at ioo0.1 It is also obtained by oxidation of trimethylpyroracemic acid with silver oxide or potassium dichromate and sulfuric acid,2 by oxidation of tertf-butylethylene with permanganate solution,3 or by oxidation of dimethyl 2,2-propanol with chromic acid.4 Schroeter reports the formation of trimethylacetic acid by rearrangement of the oxime of trimethylacetophenone to give the anilide of trimethylacetic acid, which can be hydrolyzed to give the acid.5... 

The comparison of a bis(imino)pyridine iron complex and a pyridine bis (oxazoline) iron complex in hydrosilylation reactions is shown in Scheme 24 [73]. Both iron complexes showed efficient activity at 23°C and low to modest enantioselectivites. However, the steric hindered acetophenone derivatives such as 2, 4, 6 -trimethylacetophenone and 4 -ferf-butyl-2, 6 -dimethylacetophenone reacted sluggishly. The yields and enantioselectivities increased slightly when a combination of iron catalyst and B(CeF5)3 as an additive was used. 

Acylation reactions. Methoxyacetophenones and methoxypropiophenones can be obtained from acylation of methyl phenyl ether with the corresponding acid anhydrides and acid chlorides at 70 "C over Envirocat EPZG in 35 to 72 % yield. Other important reactions catalysed by this catalyst include acylation of PhNHCOCHi to acetamidoacetophenones and 1,3,5-trirnethylbenzene to 1,3,5- trimethylacetophenone. 

Magnesium enolates derived from hindered ketones are able to initiate polymerization. For example, addition of 2, 4, 6 4-trimethylacetophenone in toluene to a suspension of (DA)2Mg results in the isolation of (DA)Mg(OC(=CH2)-2,4,6-Me3C6H2), which is found to be an excellent initiator for the living syndioselective (a > 0.95) polymerization of methyl methacrylate (equation 86). 

Asymmetric reduction of alkyl aryl ketones with trialkoxysilanes is promoted by a catalytic amount of chiral nucleophiles [39]. The reactive species is a transiently prepared hypervalent silicon hydride. 2, 4, 6 -Trimethylacetophenone was reduced with equimolecular amounts of trimethoxysilane in the presence of the monolithio salt of (R)-BINAPHTHOL (substrate Li=20 l) in a 30 1 ether-TMEDA mixed solvent at 0 °C to afford the R product in 90% ee (Scheme 21) [40]. The presence of TMEDA was crucial to achieve high yield and enantiose-lectivity. Reduction of less hindered ketonic substrates preferentially gave the... 

Closer inspection of oxime formation from the stable 2,4,6-trimethylacetophenone imine revealed the N-oxygenating activity to be sensitive to the presence of proto-typic inhibitors of the P-450 system, such as carbon monoxide, SKF 525A and DPEA1. 

Trimethylacetophenone Trimethylaluminum Trimethylamine Trimethyl arsenite Trimethylarsine... 

In the Sc(0Tf)3-LiC104-system, wider substrate scope was observed as is shown in Table 8. Each acylation reaction in the Table gave a single acylation product and formation of other isomers was not observed. Acetylation of anisole (1) resulted in excellent yield of the product (entry 1). Mesitylene (3) and xylenes were transformed to 2,4,6-trimethylacetophenone and dimethylacetophenones, respectively, in moderate yields (entries 2-5). It is noteworthy that toluene was acylated by the Sc(0Tf)3-LiC104 system to give 4-methylacetophenone in 48 % yield (entry 6) but the acylation did not proceed in the absence of LiC104. Furthermore, recovery and reuse of the RE(0Tf)3-LiC104 system were performed successfully. As shown in Table 9, the yields of 6 in the second and third uses of the catalyst system were almost the same as that in the first use. 

FIGURE 8.8 Magnetic field dependence for the photolysis of a series of benzoyl containing molecules in cyclohexanol solution obtained by time-resolved infrared spectroscopy of the carbonyl group of the resulting benzoyl radical. Key 1 = a,a,a-trimethylacetophenone, 2 = 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone, 3 = 1-benzoylcyclohexanol, 4 = 2-hydroxy-2-methy Ipropiophenone, 5 = benzoin, 6 = methyl ether benzoin, 7 = dimethyl ether benzoin, 8 = 2-dimethylamino-2-(4-methyl-benzyl)-l-(4-morpholin-4-yl-phenyl)-butan-l-one. 

Henderson and coworkers studied the reaction of MesAl with a series of aromatic ketones (25, 27, 29) to yield the precipitation of either dimethylaluminum enolates or alkoxides (see equations 9-11). In situ H NMR spectroscopic studies of the reaction between MesAl and acetophenone (29) revealed a complex mixture of products, whereas under the same conditions 2,4,6-trimethylacetophenone (25) reacts cleanly to give the corresponding enolate. The enolate compounds 26 and 28 were isolated and 26 as well as the representative alkoxide 30 were characterized by X-ray crystallography. Both 26 and 30 form dimers with a central AI2O2 core. Ab initio calculations at the HF/6-31G level indicated that both 26 and 30 are the thermodynamic products of the reactions. Equation 12 shows the alkylation and enolization reactions for the ketones 25 and 29 and... 

Trimethylacetophenone forms a dimeric sodium enolate with two chelating TMEDA ligands (6). There is significant jt-electron interaction of the metal ion with the olefinic carbons but no evidence of jt-bonding with the aromatic rings. ... 

Hudson, R.E, and Salvador , G., Reaction between the compounds of trivalent phosphorus and a-halo-2,4,6-trimethylacetophenone, Helv. Chim. Acta, 49, 96, 1965. 

In some cases where there is a considerable amount of strain in the molecule which is released upon formation of the negative ion, Ei can be larger. Figure 1 shows a series of curves with a fixed electron affinity, but varying E , with 2,4,6-trimethylacetophenone as a typical example. 

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