Glyoxal hydrates

Polyquinoxalines are prepared by the solution polymerisation of aromatic bis((9-diamines) such as 3,3, 4,4 -tetraminobiphenyl and aromatic bis(glyoxal hydrates) such as 4,4 -oxybis(phenylglyoxalhydrate) ... 

To obtain 2,5-bis(benzoxazol-2-yl)thiophene (39), two equivalents of 2-chloro-methylbenzoxazole are treated with sodium sulfide and the thiophene ring is formed with glyoxal hydrate [70] ... 

Experimental studies on the glyoxal hydration in solutions at low water content suggest an apparent third-order dependence of the reaction rate on water concentration (Eigen, 1967). The search for a third active water molecule, performed with the strategy we have outlined, has failed in vacuo the third water molecule better solvates the hydronium ion and has no active role in the reaction. This apparently confirms other views on the reaction mechanism (Sorensen and Jencks, 1987). Pursuing further the search, it has been found that a fourth water molecule plays an active role,... 

Comparable acid- (or Lewis acid) -catalysed ring closures of 2-arylthio- and 2-aryloxy- -ketones, and -2-arylthio- and 2-aryloxyacetyl- chlorides lead to 3-substituted heterocycles and 3-oxygenated heterocycles, respectively. It is possible to combine the preparation of the arylthio-ketone and the ring closure steps utilising two solid-supported reagents in a one-pot procedure, as illustrated. Formation of 3-aryl-benzothiophenes by this route can be complicated by partial or complete isomerisation to the 2-aryl-heterocycle,however using boron trifluoride as the Lewis acid produces only the 3-aryl-isomer. 3-Tosylamino-benzofurans can be prepared from aryl glyoxal hydrates. ... 

Chloropyridine-2,3-diamine (0.29 g, 2.02 mmol), glyoxal hydrate polymer (0.1 5 g, British Drug Houses), and MeOII (3 mL) were refluxed for 10 min. 6-Chloropyrido[2,3-6]pyrazine separated on cooling. From 100 parts of petroleum ether (bp 100-120°C) it gave crystals yield 0.2g (60%) mp 156 °C. 

The formation of the glyoxalate hydrate is obviously unproductive and is probably an artifact resulting from the assay being done on the isolated system. Bern-hard found that many enzymes can bind to other enzymes that occupy adjacent positions in metabolic pathways (28), transferring substrates and products without the intermediate involvement of solvent. In the case of malate synthase, the oxidation of glycolate to glyoxalate might produce material in the unhydrated form, which would be used directly. In that case, the equilibrium isotope effect on hydration would not be observed. 

The condensation of 3,4-diaminopyridine with glyoxal hydrate in alcohol gives a 50% yield of the parent heterocycle m.p. 97°. This method is more convenient than the use of the bisulfite compound in aqueous acetic acid, which provides only a low yield of the required compound. Benzil and diacetyl and l,4-dibromobutane-2,3-dione provide the expected 2,3-disubstituted products 4 in good yields. Dimethyl oxalate reacts with 3,4-diaminopyridine in refluxing M hydrochloric acid to give the open-chain compound 5." This may be cyclized to the dioxo compound 6 by heating at 230°. 

Deoxofluor reacts with glyoxal hydrate 139 to form in good yield polyfluoroethers... 

Singh, R.P. Twamley, B. Shreeve, J.M. Polyfluoroether derivatives via nucleophihc fluorination of glyoxal hydrates with deoxofluor. J. Org. Chem. 2002, 67, 1918-1924. 

Obtained by reductive condensation of p-hydroxyphenyl-glyoxal hydrate and ben-zylamine under hydrogen in the presence of Raney nickel in ethanol at 40°. Then, treatment of the mixture with 6 N ethanolic hydrogen chloride (82%) [4818]. 

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