Hydrogenation hydroxyacetone

The yield of acetone from the cumene/phenol process is beUeved to average 94%. By-products include significant amounts of a-methylstyrene [98-83-9] and acetophenone [98-86-2] as well as small amounts of hydroxyacetone [116-09-6] and mesityl oxide [141-79-7]. By-product yields vary with the producer. The a-methylstyrene may be hydrogenated to cumene for recycle or recovered for monomer use. Yields of phenol and acetone decline by 3.5—5.5% when the a-methylstyrene is not recycled (21). 

Hydrogenation gives aUyl alcohol [107-18-6] C H O, its isomer propanal [123-38-6] (20), or propanol, C H O [71-23-8] (21). With acidic mercuric salt catalysts, water adds to give acetol, hydroxyacetone, C2H 02 [116-09-6] (22). 

Similar hydroxylation-oxidations can be carried out using a catalytic amount of osmium tetroxide with A-methylmorpholine oxide-hydrogen peroxide or phenyliodosoacetate." A recent patent describes the use of triethylamine oxide peroxide and osmium tetroxide for the same sequence. Since these reactions are of great importance for the preparation of the di-hydroxyacetone side-chain of corticoids, they will be discussed in a later section. 

R)-l,2-Propanediol is an intermediate for (S)-oxafloxazin, a bactericide which until recently was sold as a racemate. The (R)-diol is now produced by Takasago via hydrogenation of hydroxyacetone (see Fig. 37.23) using a Ru-Tol-binap catalyst on a 50 t y 1 scale [92 b[. Recently, it was reported that segphos - a newly developed biaryl diphosphine - shows even better results, achieving >98% ee and TON and TOF of 10000 and 1400 h, respectively [16, 93]. 

Indigo is readily reduced by various reducing agents such as zinc dust, sodium dithionite, hydroxyacetone, and hydrogen, or by electrochemical means. In an alkaline medium, a salt (for example the sodium salt) of leuco indigo is produced (3), which can be converted by acids to so-called indigo white (2). 

Another Ru(BINAP)-catalyzed asymmetric hydrogenation that has been performed at manufacturing scale involves the reduction of a functionalized ketone. The reduction of hydroxyacetone catalyzed by [NH2Et2]+[ RuCl(p-tol-BINAP) 2 (li-CI)3 (39) proceeds in 94% ee (Scheme 12.11).46 The chiral diol (40) is incorporated into the synthesis of levofloxacin (41), a quinolinecarboxylic acid that exhibits marked antibacterial activity. Current production of 40 is 40 tons per year by Takasago International Corp.46... 

The bottom product of the pre-evaporation stage (Figure 6.7) can eventually be sub] ected to hydrogenation in a trickle bed reactor, to purify the solvent recycle stream by eliminating impurities in the form of formaldehyde and acetaldehyde, reducing them to methanol and ethanol, and also to eliminate traces of unconverted HP. Moreover, traces ofhydroperoxypropanol and hydroxyacetone are converted into 1,2-propanediol. This allows a considerable decrease in catalyst deactivation in the epoxidation reactor and the improvement of product quality [20k]. 

It is rather challenging to synthesize anti aldols from hydroxyacetone (39) owing to its propensity to favor the hydrogen bond-stabilized (Z)-enamine. Gratifyingly, organocatalytic methods give access to both the syn- and anti-diastereoisomers. 

It is believed that the hydroxyl group present in hydroxyacetone (39) stabilizes the (Z)-enamine via hydrogen bond formation, and thus the use of O-protected derivatives as donors in the direct aldol reaction required, at best, tuning the reaction conditions. Only a few catalysts were applied to the reaction of O-Bn-hydroxya-cetone (51) with various aldehydes [103, 58]. Luo and Cheng s catalyst 38 also... 

As part of the Megacity Initiative Local and Global Research Observations (MILAGRO) project, a comprehensive airborne study by Yokelson et al. reported the first detailed field measurements of biomass emissions in the Northern Hemisphere tropics [169]. Volatile emissions were measured from 20 deforestation and crop residue fires on the Yucatan peninsula. This included two trace gases which are often considered to be useful as indicators of biomass burning. One we have discussed before, namely acetonitrile, and the other is hydrogen cyanide. A variety of instrumentation was co-deployed for this investigation (FTIR spectroscopy, GD-FID, a GC-Trace Analytical Reduction Gas Detector, fluorescence and chemiluminescence instruments and various other spectrometers). PTR-MS was used to monitor methanol, acetonitrile, acetaldehyde, acetone, methyl ethyl ketone, methyl propanal, hydroxyacetone plus methyl acetate, benzene and 13 other volatile species. 

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