Product yield improvement, 4- acetophenone

A substituted acetophenone (10 g) is added to anhydrous ethanol (50 ml) previously saturated with gaseous hydrogen chloride. After storage for 30 days the mixture is filtered and the solid triarylbenzene is washed with cold ethanol. The yield is improved if the mother-liquors are poured into water, and the solid product is then collected this material is somewhat impure and must be washed several times with ethanol. Depending on the substituent in the acetophenone, the yield varies between 20% and 85%. 

For example, the effect of cultivation time and different carbon sources on the enantioselectivity of the reduction of sulcatone by some anaerobic bacteria has been investigated [8 if Another example is the investigation on the effect of the medium concentrations for cultivation of Geotrichum candidum IFO 4597 on the enantioselectivity of the reduction of acetophenone derivatives. The yield of l -alcohol (the minor enantiomer) increased with the medium concentration therefore, the medium concentration was kept low, optimally to produce the S-enantiomer[82]. The effect of the aeration during cultivation on the enantioselectivity of bakers yeast production of 3-hydroxyesters has also been reported 86 Inducers such as a substrate analog may also induce the desired enzyme to improve the enantioselectivity. 

Ethylbenzene [100-41-4] (phenylethane) has a water-clear appearance and characteristic odor. It is miscible with practically all organic solvents, but is insoluble in water. Ethylbenzene is of limited importance as a paints solvent. Its main use is as an industrial starting material for the production of styrene by catalytic dehydrogenation. Catalytic oxidation of ethylbenzene with air in the presence of heavy-metal oxides yields acetophenone and phenylmethylcarbinol. It also improves the antiknock properties of fuels for Otto engines. 

Some early work utilizing DOE in process development was reported by T. Lundstedt et al. (5). The work is based upon a Japanese patent (-/) describing the preparation of 4-(iV A/-dimethylamino)acetophenone in 77% yield by heating 4-chloroacetophenone in aqueous dimethylamine. In this study, the goal was to improve the yield of product. 

HMIM][N03]-[BMIM][Bp4] as a binary task-specific IL under microwave condition (Scheme 48). The combination of [HMIM][N03]-[BMIM][Bp4] was found to be essentially required for this transformation otherwise the reaction did not proceed well. In the course of reaction, [HMIM][N03] oxidizes aryl alcohols to aryl aldehydes that further react with acetophenone and ammonium acetate to afford the desired products. The IL [BMIM][Bp4] acts as catalyst and promoter for the later reaction. In order to evaluate the effect of co-catalyst in this methodology, authors screened the efficacy of [PIMIM][N03] in combination with other ILs and observed that the combination of [HMIM] [NO3] (150mol%) in [BMIM][Bp4] (100mol%) was the most effective system for this transformation at 96 C (200 Watt). Increasing the reaction temperature did not improve the reaction rate however, lower yield of products were obtained on reducing the temperature [183]. 

The asymmetric reaction of nitromethane with aldehydes as well as activated ketones (e.g., trifluoroacetophenone and a-ketoesters) is possible with various chiral metallic complexes or organocatalysts under atmospheric pressure with good yield and enantioselectivity. However, the Henry reaction of aryl alkyl ketones still remains problematic and challenging. Matsumoto s group also tested the very difficult reaction of acetophenone and nitromethane with quinidine. No product was observed under Ibar and only traces at 7 kbar, but application of 10 kbar resulted in a significant improvement in yield (31%) -unfortunately, no enantioselectivity was detected (Scheme 21.3). 

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