Ketones diacetyl

Ketones. diacetyl. acetophenone Fatty Acids Peptides... 

Methyl ethyl ketone is allowed to react with n-butyl or iso-amyl nitrite in the presence of hydrochloric acid to yield diacetyl monoxime (nitrosomethyl ethyl ketone) ... 

X0 to hydroxy compounds. Lower temperatures favor ketone formation and sterically hindered carbonyls, such as 2-thienyl t-butyl ketone, are not reduced. The sensitivity of desulfurization to steric factors is evident by the failure to desulfurize 2,5-di-i-butyl-3-acetylthiophene. The carbonyl groups of both aldehydes and ketones can be protected by acetal formation, as particularly cyclic acetals are stable during desulfurization in methanol at room temperature. " The free aldehydes give primary alcohols on desulfurization. Another method to obtain only keto compounds is to oxidize the mixtures of ketone and secondary alcohol with CrOs after the desulfurization. - Through the desulfurization of 5,5 -diacetyl-2,2, 5, 2"-terthienyl (228), 2,15-hexadecandione (229) has been obtained, which... 

A variant on this theme contains mixed acyl groups. In the absence of a specific reference it may be speculated that the synthesis starts with the diacetyl derivative (15). Controlled hydrolysis would probably give the monoacetate (16) since the ester para to the ketone should be activated by that carbonyl function. Acylation with anisoyl chloride followed by reduction would then afford nisobuterol (18). 

Safety. Since organic peroxides can be initiated by heat, mechanical shock, friction or contamination, an enormous problem in safety presents itself. Numerous examples of this problem have already been shown in this article. Additional examples include the foilowing methyl and ethyl hydroperoxides expld violently on heating or jarring, and their Ba salts also are extremely expl the alkylidene peroxides derived from low mw aldehydes and ketones are very sensitive and expld with considerable force polymeric peroxides of dimethyl ketene, -K>-0-C(CH3)2C(0)j-n, expld in the dry state by rubbing even at —80° peroxy acids, especially those of low mw, and diacetyl, dimethyl, dipropkmyl and methyl ethyl peroxides, when pure, must be handled only in small amts and... 

Aldehydes and ketones are formed in reactions of arenediazonium salts with derivatives of carbonyl compounds, e.g., with oximes (Scheme 10-40, Jolad and Ra-jagopal, 1973) or with diacetyl (Scheme 10-41, Citterio et al., 1982b). In most cases yields are mediocre. Better results are obtained with CO, tetraalkyltin, and Pd(OAc)2 as catalyst (Kikukawa et al., 1987). 

Reaction of aldehydes and ketones with methanol or glycols at ambient temperature in the presence of excess trimethylchlorosilane (TCS) 14 to form acetals, hexamethyldisiloxane 7, and HCl is achieved very simply [28]. Thus cyclohexanone and diacetyl react with free glycol and TCS 14 to give the acetals 392 and 405 in 95% yield [28]. Reaction of phenylglyoxal with methanol in the presence of trimethylchlorosilane 14 affords the acetal 406 in 83% yield [28], whereas catechol 79 is converted by pivaldehyde into acetal 407 in 91% yield [29] (Scheme 5.5). 

The practical effect of the condensation consists, therefore, in the conversion of methylene into > C=0. The same result is attained in a quite similar reaction by the action of nitrous acid on ketones (cf. the synthesis of diacetyl from methylethyl ketone). 

The preparative importance of the acyloins depends on the fact that they are intermediate products, from which many 1 2-diketones can be obtained. The simplest aromatic member of this group is benzil (anisil and furil are analogous) like its aliphatic prototype diacetyl CH3.CO.CO.CH3 (and like anhydrous glyoxal) it is yellow in colour. Diacetyl is obtained from methyl-ethyl ketone via the monoxime of the former compound (von Pechmann). It is remarkable that diacetyl condenses to p-xyloquinone. (Formulate). 

Aldehydes and ketones are formed in reactions with carbonyl compounds, e.g. oximes, diacetyl and CO + tetraalkyltin172 (see also Zollinger7 11). 

Table 8.17 shows the scope of the reaction of acetylcobalt tetracarbonyl with polyenes. The reactions are regiospecific with the acetyl group adding to the terminal unsaturated carbon atom of the ir-electron system to produce the E-a,p-unsaturated ketones [9]. In the reaction with fulvenes [10], only the 1-acetyl and 1,4-diacetyl derivatives are formed, with no evidence of the 2-isomer. This is an indication of the relative stabilities of the cyclic it-allyl complexes, compared with the exocyclic complex. It has been postulated that, in the reactions of conjugated systems, the initial o-allyl adduct proceeds to the products via the it-allyl complex (cf Scheme 8.1), whereas in the case of unconjugated tt-systems, the initial o-adduct is more stable and tends to undergo a further carbonylation reaction. 

D. J. Morantz and J. W. Wigley, The contrasting phosphorescence decay kinetics of diacetyl and aromatic ketone phosphors in polymeric matrices, Polymer Communication 26, 170-171 (1985). 

After phytochemical reduction was noted in the case of aldehydes and ketones, interest arose in the behavior of fermenting cells toward compounds containing several carbonyl groups per molecule, such as diketones and quinones. This class deserves special consideration because the simplest representative, diacetyl, as well as its products of reduction, acetylmethylcarbinol (3-hydroxybutanone) and 2,3-butylene glycol, are connected with the metabolism of numerous cells quinones also are biologically important. 

IV-acetyl pyrrolidines and -piperidines to the corresponding diones or ketones were similarly effected [405, 406], as were conversions of diacetyl and dibenzyl piperazines to diketo componnds by the same system (Table 5.1) [407]. Methylene groups adjacent to the N atom in tertiary polycyclic amines were oxidised by RuO /aq. NaCIO j/CCl (Fig. 5.5) [408]. A large-scale oxidation of l,4-bis(2-phenylethyl) piperazine to the dione was made by RnO /aq. Na(10 )/Et0Ac [409], and RuO /aq. Na(IO )/CCl converted dialkyl or diaryl A A -dimethyladenosines to the corresponding monoamido derivatives (Fig. 5.4) [410]. 

Problem 17.48 Use acetoacetic ester (aae) and any needed alkyl halide or dihalide to prepare (a) CH3C0CH2CH,C0CH, (b) cyclobutyl methyl ketone, (c) CHjCOCHjCHjCHjCOCH, and (d) 1,3-diacetyl-cyclopentane. ... 

A related procedure, which may be of value from the preparative standpoint, involves the preparation of /rans-nitrosomethane dimer by adding a solution of diacetyl peroxide in sec-butyl nitrite to warm sec-butyl nitrite [50]. From the product of the reaction it has been assumed that this preparation involves the generation of free methyl radicals which react with the nitrite to give nitrosomethane and alkoxy radicals. The latter disproportionate to ketones and alcohols, while the nitroso compound dimerizes. 

In contrast, hydrogenation of 1,2-diketones that proceeds via 2-hydroxy ketones exhibits marked syn or meso selectivity (Scheme 60), although the enantiomeric preference follows the general sense given in Scheme 47 (92). Thus, (i )-BINAP-Ru-aided hydrogenation of diacetyl gives a 26 74 mixture of enantiomerically pure (R,R)-2,3-butanediol and the meso diol. 

SELECTIVE OXIDATION OF METHYL ETHYL KETONE TO DIACETYL OVER VANADIUM PHOSPHORUS OXIDE CATALYSTS. 

Selective oxidation of methyl ethyl ketone to diacetyl has been studied by passing a mixture of the ketone in artificial air over vanadium phosphorus oxide catalysts in the temperature range 200-350 C. Products observed included diacetyl, methyl vinyl ketone, acetaldehyde, acetic acid and carbon dioxide. C4 products were favoured at low temperatures and at low or zero oxygen partial pressures. These results are rationalised in terms of two pathways for C2 products, namely oxidation of the double bond in the enol form of methyl ethyl ketone to yield acetic acid and acetaldehyde, and acid catalysed hydration of the keto form to yield acetaldehyde only. The C4 products are envisaged to go through a common intermediate, namely, CH3COCHOHCH3, formed by interaction between methyl ethyl ketone and lattice oxygen. 

Diacetyl (DA) is used as a flavour enhancer in the food industry and is currently manufactured from methyl ethyl ketone (MEK) in homogeneous systems via an oxime intermediate (ref.1). In principle, DA can also be manufactured by the selective oxidation of MEK and several reports have appeared in the literature which apply heterogeneous catalysts to this task (refs. 2-4). A number of reports have specified the importance of basic or weakly acidic sites on the catalyst surface for a selectively catalysed reaction and high selectivities to DA at moderate conversions of MEK have been reported for catalysts based on C03O4 as a pure oxide and with basic oxides added conversely scission reactions have been associated with acidic oxide additives (refs. 2-4). Other approaches to this problem have included the application of vanadium phosphorus oxide (VPO) catalysts. Ai (ref. 5) has shown that these catalysts also catalyse the selective oxidation of MEK to DA. Indeed this catalyst system, used commercially for the selective oxidation of n-butane to maleic anhydride (ref.6), possesses many of the desired functionalities for DA formation from MEK, namely the ability to selectively activate methylene C-H bonds without excessive C-C bond scission. 

The main entry is the total yield of ketonic material. The percentage composition of the mixture is given in parentheses. c This melting point corresponds to that of 5,6-diacetyl-2,3-dimethylbenzo[6]thiophene. d The mixture was not separated. e A small amount of an isomer was also formed. f The 2-isomer was also formed, but it was not purified. 

Diacetyl-D-erythronolactone, 112 Dialkylaminoallenes, 432 a-Dialkylamino ketones, 299 Dialkylboranes, 261, 262... 

Figure 34 shows the results for alcohol (methanol, ethanol, 1-propanol and 1-butanol), ketone (acetone and diacetyl), terpene (pinene and linalool), aldehyde (n-nonyl aldehyde) and ester (acetic acid n-amyl ester and n-butyric acid ethyl ester) of various concentrations. Because of the linear characteristics of the CTL-based sensor, the plots are located in a similar region for a certain type of gas of various concentrations where the Henry-type adsorption isotherm holds. Thus, we can identify these gases with various concentrations by simple data-processing. 

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