3,3 -Dihydroxy ketones Subject

Reactions of 4,7-phenanthroline-5,6-dione have been the subject of considerable study. It is reduced to 5,6-dihydroxy-4,7-phenanthroline by Raney nickel hydrogenation226,249 or by aromatic thiols in benzene,262 and oxidized by permanganate to 3,3 -bipyridyl-2,2 -dicarboxylic acid.263 It forms bishemiketals with alcohols226 and diepoxides with diazomethane.226 The diepoxides by reaction with hydrochloric acid form diols of type 57, R = Cl, which on oxidation with lead tetraacetate give 3,3 -bipyridyl diketones of type 58, R = Cl. Methyl ketones of type 58, R = H, are also obtained by lead(IV) acetate oxidation of the diol 57, R = H, obtained by lithium aluminum hydride reduction of 57, R = Cl. With phenyldiazomethane and diphenyldiazomethane the dione forms 1,3-dioxole derivatives,264,265 which readily hydrolyze back to the dione with concomitant formation of benzaldehyde and benzophenone, respectively. 

A variety of a-substituted ketones (a-halo, -hydroxy, -methoxy and -amino) have been converted into alkenes by reductive elimination. Obviously, this approach, depends not only on the feasibility of a-functionalization but also on the ability to introduce the a-substituent regioselectively. a-Halo ketones, which are readily prepared from the starting ketone," have been subjected to reductive elimination conditions to afford the desired alkenic products. For example, in the preparation of ( )-eriolanin (Scheme 5)," the protected dihydroxy keto ester is treated sequentially with LDA and Br to afford the a-bromo... 

Other polymers that have been subjected to studies of thermal decomposition mechanisms include synthetic rubbers [24], polyarylether ketone [25], three polyarylates based on bisphenol-A, l,l-dichloro-2,2-bis(4-hydroxyphenyl) ethylene and 4,4"-dihydroxy-3-ethoxy-benzylidenoacetophone [26], polylactide [27], polyethylene composites [28], polyvinylcyclohexane and styrene-vinylcyclohexane... 

The biochemical reduction of the C20 ketone in human subjects seems to be stereospecifically directed to the 20a-hydroxyl group. Of the eight possible 3,20-dihydroxy derivatives of pregnane and allopregnane, only those with the a configuration at Csc have been isolated from human... 

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