Dehydrogenations chemical

It is known that tropylium may be prepared from tropylidene via hydride abstraction by PhgC or MegC carbonium ions therefore, it is very likely that here too the dehydrogenation is a hydride transfer from the 1,5-dione to an acceptor. A similar dehydrogenation of chromanones to chromones, with triphenylmethyl perchlorate was reported. A study of the electrooxidation of 1,5-diones on a rotating platinum electrode showed that 1,5-diaryl-substituted diones afford pyrylium salts in these conditions and that the half-wave potentials correlate with yields in chemical dehydrogenations. 

The use of microbial 1-dehydrogenations is essential to the manufacture of corticosteroids, as chemical dehydrogenation processes are commercially non-competitive. 

Reactions with other nucleophiles follow a similar mechanism. For the reaction of Cl with poly(3-methylthiophene) in acetonitrile, the reaction stops at structure 5 (Scheme 2).128 A fully conjugated, Cl-substi-tuted product 6 can subsequently be obtained by electrochemical or chemical dehydrogenation.128 With Br and alcohols, the overoxidation... 

Chemical Synthesis. If cholesterol is heated with elemental sulfur at 150°C for several days, a mixture of PCAH results (J2), the detailed composition of which is not known. Other dehydrogenation reagents, such as selenium, catalyze the production of alkyl naphthalenes and phenanthrenes from naturally occurring terpenes (J3). Thus, in principle, it is possible that the PCAH in an anoxic sediment could result from the chemical dehydrogenation of various naturally occurring compounds. These reactions may take place slowly over the years and may be catalyzed by trace elements, elemental sulfur, and clay minerals. 

The 1,2,3,5,6,7-hexahydro-4-oxoindol-3-yl acyclo C-nucleoside 47 was formed upon catalytic reduction of the 2-hydroximinobenzofuranone derivative 46. Chemical dehydrogenation of 47 gave the tetrahydroindol-3-yl C-nucleoside 48 [87JCS(P1)581] (Scheme 14). 

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