Subject dioxo

According to the triazine nomenclature, 5-azauracil is 2,4-dioxo-l,2,3,4-tetrahydro-l,3,5-triazine (2). The subject index of Chemical Abstracts prefers s-triazine-2,4(lH,3H)-dione. Furthermore, some authors use a name derived from the lactim structure, 2,4-dihydroxy-s-triazine (3). The numbering of the substituents is the same for all these types of nomenclature. 

Intramolecular cyclisation of a 4-arylbutanoic acid system is also an important step in a convenient synthesis of the polycyclic system, chrysene, which is formulated and described in Expt 6.12. Here, methyl cinnamate is first subjected to reductive dimerisation to give methyl meso-ft,y-diphenyladipate, which is accompanied by some of the ( + )-form. The meso isomer (16) is the most easily isolable and cyclisation occurs smoothly in sulphuric acid to yield the diketone 2,1 l-dioxo-l,2,9,10,ll,18-hexahydrochrysene, which is obtained as the trans form (17) as shown in the following formulation. Clemmensen reduction of this ketone followed by dehydrogenation (in this case using selenium) completes the synthesis of chrysene. 

Dimedone was treated with two equivalents of bromine in glacial acetic acid to yield 2,2-dibromo-5,5-dimethylcyclohexane-l,3-dione. The dibromo compound was subjected to reaction with substituted 2-aminothiophenols, 2-aminophenol, thiocarbohydrazones, and triazoles to furnish spiro-(2, 6 -dioxo-4, 4 -dimethylcyclohexane)-6-substituted-l,... 

The 4,5-dioxo-l,3,2-dioxaphospholane (128) has been prepared and subjected to thermal or MS fragmentation an intense peak corresponding to (129) was found in the El mass spectrum, and thermolysis gave (130), both results in accordance with a facile formation of the arylphosphinidene oxide (129) from (128). Pyrolysis of the cyclic phosphites (131) gave a deposit on a — 195°C cold finger which according to P NMR contained some aryl phosphenite (132), the chemistry of which could be studied for the first time. A full paper has appeared on the preparation and properties of the stable ylidylphosphinidene chalcogenides (133). ... 

To a solution of 450 mg (1.1 mmol) of diazoacetate 226 in 5 mL of benzene under nitrogen was added 2 mg of rhodium(II) acetate. The mixture was heated in an oil bath at 50 °C for 4 h and concentrated under reduced pressure, and the residue was subjected to flash silica gel chromatography to give 410 mg (95%) of 3-ca bomethoxy-4,10-dioxo-3,19-epoxy-l-methylaspidospermadine 227 as a white solid. 

Except for the poly[2,6-dioxo-l,4-piperidinediyl)dimethylene] whic was highly crystalline, all other linear polymers were cunorphous. This is of course readily explained by the presence of em asymmetric center entailing the carbon atom in the 3-position in the ring moiety of the repeating unit. Additional support for the chemical structure of the polymer PCH7 was obtained from mass spectroscoplcal studies.(12) Subjecting a polymer sample (n = 2.7) to 70 eV at 270 C yielded as a major fregment... 

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