Dihydroxybenzene derivatives

Quinone (Section 24.14) The product of oxidation of an ortho or para dihydroxybenzene derivative. Examples of quinones include... 

OOMIl, 01 Mil). Similar reactions of 1,2-dihydroxybenzene derivatives 237 with various less activated 2,6-dinitrochlorobenzene derivatives provided usually low yields of the corresponding dioxins (59JCS1899, 84JHC1073). To improve the yields, especially with less activated chloronitro compounds, a two-step... 

Hasegawa and co-workers illustrated the syntheses of substituted phenazine-5,10-dioxides 236 by a dehydrative condensation between benzofuroxan 234 and dihydroxybenzene derivatives 235 catalyzed by molecular sieves at room temperature <00H2151>. 

Table 6. Association constants and free energies of complexation for complexes of 16 with dihydroxybenzene derivatives in CDCI3 at 298 2K...

Hirose, M., Yamaguchi, S., Fukushima, S., Hasegawa, R., Takahashi, S. Ito, N. (1989) Promotion by dihydroxybenzene derivative of V-methyl-V -nitro-A-nitrosoguanidine-induced F344 rat forestomach and glandular stomach carcinogenesis. Cancer Res., 49, 5143-5147... 

Dihydroxybenzene derivatives readily form complexes of the type [Pd(02CeH3R)(PPh3)2].178,179 The increased acidity of aromatic alcohols compared with aliphatic alcohols combined with the chelate effect makes these compounds much more stable than alkoxide complexes. Their stability is such that they can be subjected to further reactions involving the side chain group R to generate compounds suitable for use as indicators for immunoassay.178... 

Figure 5. Possible mechanism of antioxidant activity of dihydroxybenzene derivative.

Another example of the effectiveness of the reaction O -coronaP] arene[3]tetrazines 54, a new class of macrocyclic compounds, were synthesized efficiently in a one-pot reaction via nucleophilic aromatic substitution of 3,6-dichlorotetrazine 53 with 1,4-dihydroxybenzene derivatives 55 in warm acetonitrile (14AGE13548). 

Ma, Y. et al., Poly(binaphthyl-20-crown-6) as receptor based molecular selective po-tentiometric electrodes for catecholamines and other 1,2-dihydroxybenzene derivatives,... 

The antioxidant activity of phenol is also increased by the presence of additional hydroxyl group in the ortho or para positions. An example of such an antioxidant is TBHQ. The effectiveness of 1,2-dihydroxybenzene derivatives is attributed to a phenoxyl radical stabilised by an intramolecular hydrogen bond (11-8). The activity of 2-methoxyphenol is lower, because the generated radical cannot be stabihsed by a hydrogen bond. The antioxidant activity of 1,2-and 1,4-dihydroxybenzene is partly caused by the fact that the semi-quinone radical can be further oxidised to the corresponding o-quinone orp-quinone, respectively, by reaction with another lipid radical (Figure 11.7) or may disproportionate to the corresponding quinone and hydroquinone. 

These compounds occur mainly in natural substances (alkaloids). Chemically, they are formals of o-dihydroxybenzene derivatives, and as such they are split more easily than phenol ethers, but less easily than other cyclic acetals. 

Both hormones are pyrocatechol (o-dihydroxybenzene) derivatives, which are easily oxidized. This fact explains the histochemical reaction of the chromaffin tissue. The hormonal content of the adrenal medulla is relatively high (several mg per gm of gland). The two active substances of the adrenal medulla, epinephrine and norepinephrine, are both derivatives of phenyl ethylamine, which possesses strong pharmacologic effects. 

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