Methyl-glyoxal

Glycothioses, I, 135 Glycuronide, III, 131 Glyoxal, methyl-, phytochemical reduction of, IV, 80 —, methyl-, III, 127 phenylosazone, III, 117, 122 Glyoxylic acid, ethyl ester, II, 89 IV, 128 Goepp, Rudolf Maximilian, Jr., obituary, III, xv-xxiii... 

Toluene o-Cresol m-Cresol p-Cresol m-Nitrotoluene o-Nitrotoluene p-Nitrotoluene Benzaldehyde 2-Methyl-p-benzoquinone Benzyl alcohol Benzyl nitrate Glyoxal Methyl glyoxal Methylbutenedial Hydroxymethylbutenedial Oxoheptadienal Methylhydroperoxide Formaldehyde Hexadienyl Hydroxyoxoheptadienyl Maleic anhydride... 

The breakdown of the benzene ring to aldehydes is extremely rare and has been achieved only by ozone. A historical and classical example is the disintegration of o-xylene to a mixture of glyoxal, methyl glyoxal, and diacetyl (butanedione) in the predicted ratios [104]. From the preparative point of view, the conversion of phenanthrene into 0,0 -diformyl-biphenyl (diphenaldehyde) [1123] or o-formylbiphenyl-o -carboxylic (diphenaldehydic) acid [1124] is more important (equation 154). 

The a-substituted carbonyl compounds, glyoxal, methyl glyoxal, and chloral hydrate, react with the titanous-peroxide system to give rearranged radicals whose formation is accounted for in the same way as that of 01120110 from glycol (above) (Dixon et al., 1964 Buley et al., 1966) ... 

The following molecules with several aldehyde or ketone functions have also been identified glyoxal, methyl-glyoxal, and hydroxypropanedial (Volume 1, Section 8.4.4). 

Acetone, bromoethane, butane, chloroethane, 2-chloropropane, 1,3-cyclopenta-diene, dibromodifluoromethane, 1,1-dichloroethane, 1,1-dichloroethene, 1,2-di-chloro-l,l,2,2-tetra luoroethane, diethylether, dimethoxymethane, dimethylpro-pane, 1,3-epoxypropane, ethyl formate, glyoxal, methyl acetate, methylbutane, methyl formate, methylpropane, -pentane, propanal. 

The related compounds bis(2-mothyl-3-indolyl)glyoxal (263) and bis(3-methyl-l-indolyl)glyoxai (264) - have been prepared by the action of oxalyl chloride on the Grignard reagents derived from 2-methylindole and 3-methylindole, respectively, Eis(l-methyl-3-indolyl)-glyoxal (265) was prepared by the action of oxalyl chloride on 1-methyIindole in ether. 

Two pieces of chemical evidence support the three-membered ring formulation. The bifunctional oxazirane prepared from glyoxal, tert-butylamine, and peracetic acid (6) can be obtained in two crystalline isomeric forms. According to the three-membered ring formula there should be two asymmetric carbon atoms which should allow the existence of meso and racemic forms. A partial optical resolution was carried out with 2-7i-propyl-3-methyl-3-isobutyloxazirane. Brucine was oxidized to the N-oxide with excess of the oxazirane. It was found that the unused oxazirane was optically active. 

Acetals of A. A -dimethyl hydrazones 4, derived from glyoxal (1) and various enantiomerically pure diols (c.g., 3a-f)24, are readily prepared by transacetalization of 2. Addition of methyl-or butyllithium to 4 provides the corresponding hydrazines in good yield (70-88%) and moderate to excellent diastereoselectivity (see Table 3)4,5. 

As the reaction sequence of Scheme 12-38 can be stopped at the stage of the oo-methylglyoxal phenylhydrazone (12.78), it is possible to synthesize asymmetrically substituted formazanes (12.80, Ar = Ar ) by reacting acetone with one equivalent of a diazonium ion ArNJ under acidic conditions and then coupling the co-methyl-glyoxal phenylhydrazone with Ar NJ in alkaline solution. 

French researchers [38c] have investigated the /zetero-Diels-Alder reaction of methylglyoxylate and glyoxal monoacetal with 2-methyl-1,3-pentadiene in a microwave oven under various reaction conditions (Table 4.9). The microwave (MW) irradiation does not affect the diastereoisomeric ratio of adducts trans/cis = 70 30) but dramatically reduces the reaction time. The glyoxal monoacetal, for instance, gives 82 % adducts after 5 minutes when submitted to irradiation with an incident power (IP) of 600 W in PhH and in the presence of ZnCL (Table 4.9, entry 1), while no reaction occurs if carried out for 4h at 140 °C in sole PhH. Similarly, methylgloxylate in water at 140 °C gives 82% adducts after 3h, whereas microwave irradiation reduces the reaction time to 8 minutes (Table 4.9, entry 5). 

Exactly this problem was the subject of synthetic experiments carried out by J. Oro et al. (1984), which were intended to clarify the possible formation of these condensation agents. They used simple compounds, such as formaldehyde, acetaldehyde, glyoxal and ammonia as starting materials, and were able to synthesize imidazole as well as its 2- and 4-methyl derivatives. 

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