Catechols dehydrogenation

Generally the di-dihydrodiols are dehydrogenated to the corresponding catechol. In some, dehydrogenation is not reqnired and elimination of CO2H, NHj, Hal, NOj", and SOj or exceptionally OH prodnces catechols directly. These are assigned to group II. 

In these reactions, dehydrogenation is not reqnired and formation of the catechol is attained with... 

Aerobic degradation of chlorinated arene hydrocarbons, including the important group PCBs, and chlorobenzoates that are produced from them as metabolites, is generally initiated by dihy-droxylation of the rings to dihydrodiols followed by dehydrogenation to catechols. Halide may be lost simultaneously and for 2-halogenated benzoates, both halide and carboxyl. Salient aspects are summarized, and attention drawn to selected aspects of enzyme inhibition. 

Incorporation studies have clarified the relative importance of the two routes that lead to the catechol metabolite of phenytoin, namely phenol oxidation and dihydrodiol dehydrogenation (Fig. 10.8, Reactions e and/, respectively) [80], Indeed, upon incubation of phenytoin in an 1802 atmosphere, two atoms of 180 are incorporated into the catechol when formed via phenol oxidation, but only one when formed via dihydrodiol dehydrogenation. This elegant study showed quite clearly that most of the catechol (75 10%) came from the phenol, indicating a comparatively slow dehydrogenation of the dihydrodiol. 

Biological. A mutant of Pseudomonas putida dihydroxylyzed benzene into cA-benzene glycol, accompanied by partial dehydrogenation, yielding catechol (Dagley, 1972). Bacterial... 

Another alternative (Scheme B) would be that an intermediate quinonemethide (e.g. XXV) dehydrogenates an easily oxidizable species, such as dihydroxydiphenylmethane, catechol, or />,p -dihydroxystilbene. The dehydrogenation of phenolic diphenylmethanes to highly colored quinonemethides has been reported by Harkin 20) and Rothenberg and Luner 37). The resulting ionized quinonemethide XXVII is likely to be quite stable because of the resonance stabilization. 

Novel carbonylative carbocyclizations of 1,6-diynes promoted by Ru3(CO)i2/P(hex-c)3 in the presence of HSiMc2Bu-Z give bicyclic o-catechol derivatives by incorporating two carbon monoxide molecules as the 1,2-dioxyethenyl moiety (equations 148 and 149)346. This reaction is tolerant of functional groups such as ester, ketone, ether and amide. The disilylated product 366 is formed through dehydrogenative silylation of the initially formed mono-silyl product 365 under the reaction conditions. 

Smith and co-workers reported the dehydrogenative borylation of ethylene with catecholborane in the presence of decamethyltitanocene Cp2 Ti catalyst to produce 5-vinyl catechol boronate 137. Reaction of Cp2 Ti with ethylene leads to the formation of metallacyclopropane species 135 that undergoes reaction with catecholborane 38a to... 

Dehydrogenation of enones. Tl(OAc)3 can be as effective as DDQ or benzene-selenenic anhydride for dehydrogenation of a, 3-enones to 1,4-dienones. However, in some cases the reaction involves dehydrogenation, acetylation, and aromatization to catechols, as in the oxidation of 1 to 2. 

The results of Table 10 confirm that the Fe (ROOH) + adducts are effective dehydrogenation agents for substrates such as cyclohexadienes, substituted hydrazines, catechols, and thiols. For PhNHNHPh and 3,5-t-Bu2-l,2-(OH)2C6H2, the reaction efficiencies are comparable for HOOH and m-C1C6H4C(0)00H as the oxidant but somewhat reduced for... 

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