Dibenzo-1,4-dioxane

C4 diene. Cr. diene, benzene, toluene, benzoquinone. phenol, naphthalene, diphenyl, diphenyl ether, dibenzofuran. diphenyl 850. 900. ketone. 4-hydroxy diphenyl. 3-hydroxy diphenyl, 4-penoxy phenol. 980 dibenzo-1,4-dioxan. 4-hydroxydiphenyl ketone. 1.4-diphenoxybenzene... 

Klecka GM, DT Gibson (1979) Metabolism of dibenzo[l,4]dioxan by a Pseudomonas species. Biochem J180 639-645. 

The behaviour of the dibenzo-18-crown-6 derivative is similar, yet the highest attainable rate is only one eighth of that observed with dicyclohexyl-18-crown-6, which points to an important difference in reactivity between crown ether-separated ion pairs. Compared to tetrabutylammonium phenoxide, the dicyclohexyl-18-crown-6/K+ phenoxide was 2.6 times less reactive. The addition of 0.05 M dicyclohexyl-18-crown-6 to dioxan resulted in the alkylation rate constant becoming the same as that observed in pure tetraglyme. 

Hirao et al. (1978a,b) have reported similar results. The rate of reaction of sodium phenoxide with 1-bromobutane was 88 times faster in dimethoxy-ethane than in dioxan. The presence of 0.135 M dibenzo-18-crown-6 [11] in dioxan completely levelled out the difference with dimethoxyethane. It is... 

The arylation of potassium phenoxide has been studied by Litvak and Shein (1976). In the absence of crown ether the rate of reaction with p-nitrobromobenzene in various solvents increases in the order dioxan < methanol < pyridine < DMSO. In the presence of either 18-crown-6 [3] or dibenzo-18-crown-6 [11], the order of the reaction rates in dioxan and methanol is reversed (Table 22). The effect of crown ether addition on the rate... 

Katritsky and co-workers ° reacted primary amines with the triflate salt of 5,6,8,9-tetrahydro-7-phenyl-dibenzo[c, /tjacridine to generate the corresponding A -substituted acri-dinium triflate salts, which on refluxing in dioxane in the presence of benzyltrimethylammo-nium nitrate, yield the corresponding nitrate esters. 

Photocycloadditions of naphthalene derivatives to alkcnes have been recently reviewed.60 Examples of such reactions are the photocycloaddition of naphthalene to 2,3-dihy-drofuran,61 of 4-methoxy-l-naphthonitrile to acrylonitrile62 and of 2-trimethylsiloxynaph-thalene to methyl acrylate.63 2-Naphthols undergo cycloaddition with ethene in the presence of aluminum trihalides only.64 Other bicyclic aromatic compounds, e.g. A-acylindoles65-67 and /V-methylphenanthrene-9,10-dicarboximide,68 have also been studied in detail. Irradiation of 5/f-dibenzo[u,i7]cyclohepten-5-one (21) and dimethyl 2-methylfumarate (22) in dioxane gives the cyclobutane adduct 23 in 73% yield.69... 

The CD spectrum of the 1,2-dibenzoate 6 in 9 1 MeOH/dioxane showed a pair of typical exciton-split Cotton effects with opposite signs centred upon the UV absorption (227 nm) of the benzoate chromophore AE235 5 -15.9 and A 221 5 +6.66. The negative longer wavelength Cotton effect clearly defines the negative chirality between the two electric transition dipoles of the benzoate chromophores... 

The reaction of iV-(2,4-dinitrophenyl)amino acids with base in aqueous dioxane has been shown to give benzimidazole iV-oxides (7). The rate-determining step is likely to be formation of an iV-alkylidene-2-nitrosoaniline intermediate (6), which is followed by rapid cyclization and decarboxylation.19 The loss of carbon dioxide from perbenzoate anions has been investigated by mass spectrometry and electronic structure calculations. The results, including isotopic labelling experiments, support a mechanism involving initial intramolecular nucleophilic attack at either the ortho- or ipso-ring positions. They also indicate that epoxides may be intermediates en route to the phenoxide products.20 There has also been a theoretical study of the formation of trichlorinated dibenzo-/ -dioxins by reaction of 2,4,5-trichlorophenolate ions with 2,4-dichlorophenol.21... 

Phase-transfer catalysis in the chemistry of 1,3-dioxanes 92MI8. Polychlorinated dibenzo-/ -dioxines 91CLY158. 

Dioxin is a common name for dibenzo-l,4-dioxane, which is 1,4-dioxane fused with two benzene rings. The name dioxin is often used incorrectly in the news media for 2,3,7,8-tetrachlorodibenzodioxin (TCDD), a toxic contaminant in the synthesis of the herbicide called 2,4,5-T or Agent Orange. Surprisingly, TCDD has been in the environment for many millions of years because it is also formed in forest fires. Most dioxins are toxic and carcinogenic (cause cancer) because they associate with DNA and cause a misreading of the genetic code. 

A further variation has been proposed by Pless with the 10,ll-dihydro-5//-dibenzo[a,rf]cy-clohepten-5-yl derivative (dibenzosuberyl. Sub, 113), in which two phenyl groups are linked via an ethylene bridge.The Sub group represents an alternative to the more commonly used trityl group, since it is more stable under acidic conditions (stable even against 5 M HCl/ dioxane), but cleaved by various hydrogenolytic or acidolytic procedures, e.g. 10% TEA/... 

The 10,ll-dihydro-5//-dibenzo[a,d]cyclohepten-5-yl (5-dibenzosuberyl) group was proposed by PlessP l as a system with broad applications in amino, hydroxy, sulfanyl, and also carboxy protection. The ester is prepared from N-protected amino acids with 5-chloro-10,ll-dihydro-5//-dibenzo[a,d]cycloheptene/TEA in dioxane (reflux, 4h). It is cleaved like tert-butyl esters by acid hydrolysis with aqueous HCl/THF (rt, 30 min) or with neat TFA it is also removed by catalytic hydrogenolysis. 

Diphenyl Tellurium Dibenzoate 3.5 g (10 mmol) of diphenyl tellurium dichloride are dissolved in 50 m/ of dioxane and 5 g (22 mmol) of silver benzoate are added to the stirred dioxane solution at 20°. The mixture is then heated under reflux for 4 h, filtered, and the filtrate evaporated. The residue is recrystaUized from benzene/hexane (1/9, v/v) yield 4.8 g (92%) m.p. 161°. 

Diode array-UVD (DA-UVD) 953 1,3,2-Dioxaborins, formation of 683 Dioxanes—see 1,3-Benzodioxanes Dioxepens—see Dibenzodioxepens Dioxins—see Dibenzo-p-dioxins Dioxiranes, as oxidants 1255, 1257, 1258 Dioxocines—see Dibenzodioxocines Dioxygen-copper complexes, as oxidants 1194, 1198... 

Dioxo-(tetrabenzo-cis-anti-cis-tricy lo[7.5.0.02 8] tetradccatetraen-(3,6,10,13))3 8,2 g (40 mMol) 5-Oxo-7H-(dibenzo-(a e]-cycloheptatricn) in 75 ml abs. 1,4-Dioxan werden 9 Stdn. mit einer Queeksilber-Hochdruck-Lampe (Hanau Q 400) belichtet. Man dampft das Losungsmittcl ab und crhiilt nach Zugabc von Aceton 5,1 g (02%) des Dimeren. 

The p-quinonemethide route, introduced in the late 1980s,starts with the reaction of a p-H-calixarene with HCHO and a dialkylamine to produce a Mannich base, followed by methylation of the Mannich base to give the quaternary salt, and treatment with two equivalents of a nucleophile to produce a p-CH2Nu-calixarene, as illustrated by the conversion of 194 to 196. The Mannich reaction appears to occur with greater facility with the fully hydroxylated calixarenes than with their partial ethers, perhaps a consequence of the greater acidity of the former. For example, 4 reacts smoothly at room temperature (24 h) to afford the tetrakis(dimethylaminomethyl)calix[4]arene, whereas its A,C-dimethyl ether fails to react under these conditions and requires 66 h reaction time in refluxing dioxane. The A,C-dibenzoate and the A,C-diallyl ether of 4 both fail to undergo the Mannich reaction even at 140°C. ... 

R)-Spirobi-1,4-dioxan (212) has been prepared from 2-chloro-ethyl 3-D-fructopyranoside.220 A study of the half-chair conformations of compounds (213 X and Y = or S or S02 R1, R2=a variety of substituents or benzo) has been made using H n.m.r. spectros-copy,221 and the conformation of dibenzo-1,4-dioxin is folded about the 0-0 axis at an angle of 16S3 according to an n.m.r. study.222 Tetrachlorodibenzodioxin is a very stable compound but electrolysis in the presence of other oxidizable compounds breaks down the molecule.22 3... 

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