Diacetyl production

Pentafluorophenyl acetate is a highly selective acetylating reagent, useful for acetylations at hydroxyl and amino groups under mild conditions When applied to the acetylation of amino alcohols, it gives selective formation of H acetyl derivatives at room temperature and M,0 diacetylated products under moderate heating in the presence of triethylamine [149]... 

Singer and co-workers have investigated the acylation reactions of ferrocene in ionic liquids made from mixtures of [EMIMJI and aluminium(III) chloride (Scheme 6.1-5) [9, 10]. The ionic liquid acts both as solvent and as source of the Friedel-Crafts catalyst. In mildly acidic (X(A1C13) > 0.5 [EMIM]I/A1C13, the monoacetylated ferrocene was obtained as the major product. In strongly acidic [EMIM]I/AlCl3 X(A1C13) = 0.67 the diacylated ferrocene was the major product. Also, when R = alkyl, the diacetylated product was usually the major product, but for R = Ph, the monoacetylated product was favored. 

When the starting material contains a methyl or phenyl substituent in the 4-position, the acetylation with acetic anhydride can be directed towards the mono- and diacetylated product 8 and 9, respectively.176... 

The cathodic reduction of quinoxaline or 4-methylcinnoline in the presence of acetic anhydride affords diacetylated products [264] as depicted in Scheme 146 for quinoxaline. 

No studies were located regarding the metabolism of 3,3 -dichlorobenzidine in humans following dermal exposure. In a 24-hour urine sample of rats given a single dermal application of 3,3 -dichlorobenzidine (50 mg/kg/day), -diacetyl 3,3 -dichlorobenzidine (but not/V-acetyl 3,3 -dichlorobenzidine or the unchanged chemical) was detected (Tanaka 1981). Since the mutagenicity of diacetylated product is much less than either the monoacetylated or parent compoimd (Lazear et al. 1979 Reid et al. 1984 ... 

Ring closure of 167 to thiazolo[3,2-b][l,2,4]triazoles can also be effected by acid anhydride, but the course of the reaction depends on the starting materials. Refluxing 167 with acetic or propionic anhydride (3-4 h) leads directly to 176. With pentafluoropropionic, heptafluorobutanic, and benzoic anhydride only diacetylated products 177 were produced (further details [76JHC(13)1225]). 

Richter, R. L., Brank, W. S., Dill, C. W. and Watts, C. A. 1979. Ascorbic acid stimulation of diacetyl production in mixed-strain lactic acid cultures. J. Food Prot. 42, 294-296. 

Pack, M. Y., Vedamuthu, E. R., Sandine, W. E. Elliker, P. R. and Leesment, H. 1968. Effect of temperature on growth and diacetyl production by aroma bacteria in single-and mixed-strain lactic cultures. J. Dairy Sci. 51, 339-344. 

The acetylation of compound (78) has been reported under a variety of conditions. Reaction of (78) with acetic anhydride at 50 °C gives the diacetyl product (79). However, when the acetylation is carried out at 120 °C the cyclized product (80) is obtained. This latter product can also be obtained by reacting the diacetyl intermediate (79) with acetic anhydride at 120 °C. Hydrolysis of (80) in IN aqueous sodium hydroxide at 80 °C regenerates (79) (76CPB2637). 

Neri et al89 reported the desymmetrization of A-Boc-serinol 98 by the selective monoacetylation using PPL (porcine pancreas lipase) and vinyl acetate as the acylating agent in organic solvent. The mono acetylated product (R)-99 was obtained after 2 hours with 99% ee and isolated in 69% chemical yield. Traces of the diacetylated product 100 were observed. The cyclization of (R)-99 in basic medium afforded the racemic oxazolidinone 101. The latter was subjected to enzymatic hydrolysis in phosphate buffer affording (R)-... 

During the first 2h of reaction, a decrease in AcOH conversion (from 48 to 43 %) for benzene acetylation at 523 K with an increase in selectivity to the monoacetylated product (from 80 to 90%) can be observed. The only problem involves the low catalyst activity 1.5 mmolh 1g 1 of acetophenone, which corresponds to a TOF value of 2.2 h-1. This means that less than 0.2 g of this acetylated arene can be produced per hour and per gram of catalyst under the operating conditions (i.e. 10 times less than in the liquid phase acetylation of anisole with AA). The kinetic study of the reaction shows an increase in the selectivity with the substrate/acetic acid ratio, but no increase in yield, an increase in acetic acid conversion with the reaction temperature with a significant decrease in selectivity due to a greater formation of diacetylated products.[62,63] HFAU and RE-FAU zeolites do... 

Tetramethyl-l,l -diarsaferrocene 21 (E = As) can be acetylated with acetyl chloride in the presence of aluminium chloride (Scheme 1) <19950M2689>. Acetylation with 1 equiv of acetyl chloride gives the monoacetyl product 23 in 54% yield. Acetylation with an excess of acetyl chloride gives a mixture of diacetylated products 30 and 24 in the ratio of 3 5. 

Martineau, B., Henick-Kling, T. (1995). Performance and diacetyl production of commercial strains of malolactic bacteria in win. J Appl. Bacterial, 78, 526-536. 

The situation with regards to diacetyl is less clear, as diacetyl production is highly variable, and as the detection threshold is cultivar dependent (54). 

Since the two rings become chiral, the diacetylated product is a mixture of two separable diastereoisomers. 

For a ROSENLEW reactor 2.5 m in diameter, making 350 kg/h of furfural, the ratio of diacetyl production to furfural production is 0.01396, and the ratio of 2,3-pentanedione production to furfural production is 0.00118. Thus, if furfural sells for 1 US per kg, the ratio of the sales value of diacetyl to the sales value of furfural is found to be... 

The enterococci contribute to the ripening and aroma development of cheese due to their proteolytic and esterolytic activities, as well as their diacetyl production by citrate metabolism (Centeno et al. 1999). The presence and growth of enterococci in cheeses and sausages results in organoleptically unique products, which contribute to the local cuisine and the region s heritage. Due to interlinked European and worldwide markets, these cheeses are widely distributed and are internationally considered as delicacies (Franz et al. 1999). 

The work-up conditions for the condensation step (Scheme 12.6) were also modified to accommodate commercial operations. Sodium carbonate was used in the initial chemical development pilot plant batches to absorb the by-product HCl from the reaction. The quantities of carbon dioxide produced from the neutralization made this approach impractical in a commercial plant. To complicate matters, the amide bond formed during the condensation was subject to hydrolysis under strongly acidic conditions. Solid sodium acetate was added to the reaction mixture as a buffer to address this issue. A significant quantity of the diacetylation product (18) was also detected in the reaction mixture before work-up. However, this material rapidly hydrolyzes to the condensation product (6) and 2-chloronicotinic acid upon exposure to water (Scheme... 

Concerning the compounds adsorbed on the active sites of the catalyst that can decrease the acetylation rate, two classes of products have been recognized after zeolite mineralization. Monoacetylated products are observed from anisole, whereas comparable amounts of mono- and diacetylated products are observed from 2-methoxynaphthalene (2-MN), meta-xylene, and 2-methylnaphthalene essentially, diacetylated products are observed from toluene. This behavior is related to the difference in polarity between the substrates and the acetylated products, the... 

The first example of a diacetylated product (284) was also encountered in this study, as was the formation of a 3-benzoyl product (285). This orientation presumably arose from a steric effect associated with the use of the more bulky reagent benzoyl chloride for attack on the ring. 

Hugenholtz, J., Kleerebezem, M., Starrenburg, M., Delcour, J. et al (2000) Lactococcus lactis as a cell factory for high-level diacetyl production. Appl. Environ. Microbiol, 66, 4112-4114. 

Figure 8.2 Pyruvate branch with diacetyl production and citrate metabolism. Underline indicates reactions that have to be modified to increase diacetyl production (for further explanation, see text).

Genome-scale metabolic models Lactococcus lactis IL1403 First LAB genome-scale model metabolic engineering of central metabolism for diacetyl production Oliveira et al. (2005)... 

Metabolic engineering strategies Increasing diacetyl production in Lactococcus lactis... 

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