Benzene dioxo compounds

Quinones aromatic dioxo compounds derived from benzene or multiple-ring hydrocarbons such as naphthalene, anthracene, etc. They are classified as Benzoquinones (see). Naphthoquinones (see), An-thraquinones (see), etc. on the basis of the ring system. The C = O groups are generally ortho or para, and form a conjugated system with at least two C = C double bonds hence the compounds are colored, yellow, orange or red. This type of chromo-phore is found in many natural and synthetic pigments. 

In cyclic sulfoximides such as 3-ethoxy-4,5-dihydro-3-oxo-l-phenyl-and 3,4,5,6-tetrahydro-3,5-dioxo-1 -phenyl-1H-1 A6,2,4-thiadiazine 1 -oxides (46), the C6 proton signals appear at much higher fields [4.35 and 4.9 ppm (2H)] than for aromatic systems [benzene, 7.27 ppm thiophene, 7.2 (C2-H) and 6.95 ppm (C3-H)]. Similarly, the, 3C-NMR signals of the C6 atom appear at higher fields. These facts suggest a degree of ylidic character (77JOC952), which can be demonstrated by the reactivity of such compounds towards electrophiles (see Section III, C,3,f). 

Most of the diorgano alkylidene tellurium compounds thus far reported derive their alkylidene group from 5,5-dimethyl-l,3-dioxocyclohexane. These diorgano cyclohexyl-idene tellurium compounds are colorless, crystalline substances that are stable at 20° and readily soluble in benzene, carbon tetrachloride, and dichloromethane2,3. Single crystal X-ray diffraction showed that the tellurium atom in bis[4-methoxyphenyl] 5,5-dimethyl-l,3-dioxo-2,2-cyclohexylidene tellurium occupies the apex of a trigonal pyramid4. 

A mixture of dry Pb-tetraacetate and Ga-carbonate refluxed briefly in abs. benzene, cooled, 3,17-dioxo-19-hydroxy-Zl -androslene added, and refluxed 14 hrs. 3,17-dioxo-10j -aceloxy-zj -estrene. Y 77%. based on startg. m. consumed.—The reaction is critically influenced by the choice of the solvent and independent of steric factors. It makes available by straightforward synthesis compounds which otherwise can be obtained only by multi-step procedures. F. e. s. M. Amorosa et al., Helv. 45, 2674 (1962) without CaCOg cf. F. Alvarez, Steroids 3, 13 (1964). 

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