Benzo dioxins

Figure 2. Photoreduction of 2,3,7,8-tetrachlorodi-benzo- -dioxin (I) (2 mg/liter in methanol) as compared with that of the 2,3,7-trichloro-homolog (II) (20), 1971 by AAAS...

Photooxygenations of 1,4-dioxins and their benzo- and naphtho derivatives as well as the ozonolyses of 1,4-benzo-dioxins and the cycloaddition of dithiins and 1,4-benzodithiins have been reported <1996CHEC-II(6)447>. In more recent reports, 2-chloro-l,4-benzodithiin-l,l,4,4-tetraoxide 67 was employed as a very reactive dienophile <19970393, 2005JOC5221> and was suggested as a mild alternative to the use of benzyne in [4-1-2] cycloaddition reactions (Scheme 7) <1996T14247>. 

Gas chromatography-mass spectrometry has been used to determine 2,3,7,8-tetrachloro-p-benzo dioxin in soil [226]. 

The first report on the peroxidase transformation of dioxins was published by Hammel et al. in 1986 [116]. They transformed dibenzo[p]dioxin and 2-chlorodi-benzo / dioxin with lignin peroxidase from P. chrysosporium. Later on, with the aim to elucidate the pathway for the fungal degradation of 2.7-dichlorodi ben7.0-p-dioxin. the oxidation products generated by lignin peroxidase and manganese peroxidase... 

SYNS DECAHYDRO-4a,7,9-TRIHYDROXY-2-METHYL-6,8-BIS(METHYLAmNO)-4H-PYRANO(2.3-b)(l,4)BENZO-DIOXIN-4-ONE DIHYDROCHLORIDE, (2R-(2-a,4a-P,5a-... 

Azzaoui, K., Lafosse, M., Lazar, S., Thiery, V. and Morinallory, L. (1995a). Separation of Benzo-dioxinic Isomers in LC. A Molecular Modeling Approach for the Choice of the Stationary Phase. J. Liquid Chromat., 18, 3021-3034. 

Abbreviations used in text AA, arachidonic acid AhR, aryl hydrocarbon receptor Amt, AhR nuclear translocator BR, bilirubin BV, biliverdin CYP1A1, cytochrome P4501A1 DRE, dioxin responsive element FICZ, 6-formylindolo(3,2b)carbazole HAH, halogenated aromatic hydrocarbon I3C, indole 3-carbinol ICZ, indolo-(3,2,-b)-carbazole PAH, polycyclic aromatic hydrocarbon RAR, retinoic acid receptor TCDD, 2,3,7,8-tetrachlorodi benzo-/>-dioxin Trp, tryptophan UGT 01, UDP-glucuronosy 1 transferase 01... 

Alternatively, a recent study by Dulin and coworkers ( ) found no photoproducts for 2,3,7,8-TCDD in either water or hexane, despite a careful analysis of the reaction solution for 2,3,7-trichlorodi-benzo- -dioxin. They suggested that cleavage of one Ar-0 bond is an alternative photochemical pathway which may predominate during 2,3,... 

The oxidation of 1,4-benzodioxins has been well investigated. Thus, oxidation of the 1,4-benzo-dioxin (42) by w-chloroperbenzonic acid afforded the 1,2-benzoquinone (43) in moderate yields. On the other hand, when (42) was oxidized by a -butyl hydroperoxide-vanadium catalyst system, followed by treatment with potassium carbonate, 1,2-benzoquinone (43) was obtained in good yield, because of the suppression of the formation of nucleophilic by-products <87JHC785>. 

As above (Section 6.09.5.2.1), the oxygenated ring of benzodioxin is relatively unstable towards electrophilic agents. However, reaction of ethyl 1,4-benzodioxin-2-carboxylate (39) and 1,4-benzo-dioxin-2-carbonitrile (47) with acyl chlorides in the presence of aluminum chloride in an inert solvent affords regiospecifically the corresponding acylated products (48) and (49), in excellent yields <95T2619>. 

Hydroxymethyl-1,4-benzodioxin (137) obtained in 80% yield by reduction of ethyl 1,4-benzo-dioxin-2-carboxylate (39) with lithium aluminum hydride in refluxing ether <91TL5525> reacted with zinc azide bis-pyridine complex under Mitsunobu conditions (triphenylphosphine, diisopropyl azodicarboxylate) to yield exclusively compound (138) in 75% yield. Otherwise, (137) was first reacted with zinc iodide under the same conditions until complete transformation of the starting material into the mixture of regioisomers (139) and (140) excess of dry piperidine was then added to the crude reaction medium to yield the alkenic analogue (141) of Piperoxan <89TL1637>. 

The lethal doses of the various very toxic compounds can vary over a wide range the LD50 value of the well-known Seveso poison 2,3,7,8-tetrachloro-di-benzo-dioxin (TCDD) indicates higher toxicity than potassium cyanide by a factor of 10 000, but it is less toxic than botulinus toxin by nearly the same factor. 

Less is known about 2,3-dihydro-5 -l,4-benzodioxepins. The parent member of this class of compounds (69) and its halogenated derivatives (68) and (70) could be obtained from 1,4-benzo-dioxin (66) by dihalogencarbene addition, thermolysis, and reduction (Scheme 6) <83AG(E)64>. 

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