1.4- Benzodioxins

Mellis and F. Sotgiu, Rend. Semin. Fac. Sci. Univ. Cagliari, 1978, 48, 261. 

Asakawa, Y. Fukushima, E. Imamiya, and Y. Kawamatsu, Chem. Pharm. Bull., 1979, 27, 522. 

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Chemicel Neme 2-[2,3-Dihydro-3-(4-hydroxy-3-methoxyphenyll-2-(hydroxymethyll-1,4-benzodioxin-6-yl] -2,3-dihydro-3,5,7-trihydroxy-4H-1 -benzopyran-4-one... 

Intramolecular cyclization can yield fluorinated phenoxazines by a Smiles rearrangement (86IZV1855) and 2,3-dihydro-l,4-benzodioxins by a base-induced reaction [81JFC(18)483]. 

CN l-(4-amino-6,7-dimethoxy-2-quinazolinyl)-4-[(2,3-dihydro-l,4-benzodioxin-2-yl)carbonyl]piperazine hydrochloride... 

RN 2165-19-7 MF CioH.jNjO MW 207.23 CN [(2,3-dihydro-l, 4-benzodioxin-2-yl)methyl]guanidine... 

Cyclopenta[fc]dioxanes (44) are accessible from the reaction of the dioxenylmolybdenum carbene complex (43) with enynes <96JOC159>, whilst an intramolecular and stereoselective cyclisation of (Ti5-dienyl)tricarbonyliron(l+) cations affords chiral frans-2,3-disubstituted 1,4-dioxanes <96JOC1914>. 2,3-Dimethylidene-2,3-dihydro-1,4-benzodioxin is a precursor of the 3,8-dioxa-lff-cyclopropa[i]anthracene, which readily dimerises to dihydrotetraoxaheptacene (45) and the analogous heptaphene <96AJC533>. 

When chlorinated phenols are heated for analytical purposes with calcium hydroxide-potassium nitrate mixtures, chlorinated benzodioxins analogous to the extremely toxic tetrachlorodibenzodioxin may be formed. 

This intramolecular etherification approach has successfully been applied to the syntheses136 of siccanin137 and clusifoliol,136 and a formal synthesis of morphine.138 Examples of tandem inter- and intramolecular etherification reactions have also been reported which convert catechol and o-aminophenol derivatives into benzodioxins (Equation (24)),139-141 benzodioxepines,142 and morpholines.139,140... 

Chemical/Physical. TCDD was dehalogenated by a solution of poly (ethylene glycol), potassium carbonate, and sodium peroxide. After 2 h at 85 °C, >99.9% of the applied TCDD decomposed. Chemical intermediates identified include tri-, di-, and chloro[Ae]dibenzo[l,4]dioxin, di-benzodioxin, hydrogen, carbon monoxide, methane, ethylene, and acetylene (Tundo et al., 1985). TCDD will not hydrolyze to any reasonable extent (Kollig, 1993). 

MDL 73005 = 8,2 (2,3-dihydro-l,4-benzodioxin-2yl) methylamino-ethyl-8-azaspirol (4,5) decan-7,9-dione NAN 190 = l-(2-methoxyphenyl) 4-(4(2-phthalimido)entyl-piperazine)... 

The X-ray structures of two l,3-benzodioxin-4-one derivatives (28 in Scheme 17) were reported [83T3151 90AX(C)2416] the dioxane ring was present in a half-chair conformation with the alkoxy (phenoxy) substituent in an axial orientation. 

The double )5-scission pathway becomes dominant in bicyclic systems (Equations (7)-(9) and Scheme 13). Thus, cyclopentene ozonide (69) gives cyclopropane (Equation (7)) <68TL329l>. Photolysis of the ozonide derived from 1,4-benzodioxins (70) provides a method for the preparation of labile o-benzoquinones (71) (Scheme 13) <87JOC56l6>. Photolysis can also provide a route to unstable compounds and transient species such as the aziridine-2,3-dione (72) (Equation (8)), identified at 77 K using infrared spectroscopy <80JA6902>. Relatively unstable azacarbapenems (73) have been prepared by photolysis of tricyclic compounds containing a cyclobutene ozonide (Equation (9)). On silica, the 1,2,4-trithiolane (74) underwent photo-equilibration (Equation (10)) with the 1,3-dithetane (75) and sulfur. 

The formation of l,4-dihydro-2,3-benzodioxin 5 from the benzocyclobutene 141/o-quinodimethane 142 equilibrium has been utilized as a trapping experiment for the kinetic analysis of diradical reactions (Scheme 38) <2002CC1594, 1988CB1357>. 

A//abs) were employed as predictors of the antioxidant activity of vitamin E and its analogs <1997HCA1613>. A number of 4//-l,3-benzodioxin-6-ol derivatives 40 were evaluated in this way and a series of 4//-l,3-benzodioxin... 

A l,3-benzodioxin-2,4-dione containing an anhydride and a carbonate moiety was used for the preparation of biologically active compounds. It was reacted with 3-bromoaniline in such a way that the amino group attacks the anhydride moiety to give the carbamate rather than the expected amide (Equation 21) <2004JME6948>. 

Most partially saturated ring systems, 2,3-dihydro-l,4-dioxin 10 (sometimes named as 1,4-dioxene), 2,3-dihydro-1,4-dithiin 11, 2,3-dihydro-l,4-oxathiin 12, 2,3-dihydro-l,4-benzodioxin or 1,4-benzodioxane 13, 2,3-dihydro-l,4-benzodithiin 14, and 2,3-dihydro-l,4-benzoxathiin 15 are well investigated. Ring numbering for compounds 10-12 is followed as shown, independently of the presence of substituents. 

Vibrational frequencies of 1,4-benzodioxin using the density functional theory (DFT) method, as well as the conventional HF and MM3 force-field methods, were calculated to evaluate the frequency prediction capability of each computational method and get a better understanding of the vibrational spectra . 

For compound 22, X-ray analysis demonstrates that the dioxane ring adopts the chair conformation and that the imidoyl amino group prefers an axial conformation <2002T2621>. For (l,4-benzodioxin-2(3//)-yl)methyl sulfamic acid ester 21, the conformation of the dihydrodioxin ring is close to an ideal half-chair and for 1,2,4,6,7,9-hexafluoro-... 

Since the publication of CHEC-11(1996), only a few papers deal with the reactivity of 1,4-benzodioxin. For example, as shown in Equation (1), treating 4 with AT-iodosuccinimide (NIS) or AT-bromosuccinimide (NBS) followed by an appropriate nucleophile gave various 2,3-disubstituted-l,4-benzodioxanes 32 in a simple one-pot procedure <2001HC0135>. 

Subjected to a mixture of nitric acid/acetic acid, ethyl l,4-benzodioxin-2-carboxylate did not lead to the expected 6-substituted product but led to a complicated mixture from which 52% of ethyl 3-nitro-l,4-benzodioxin-2-carboxyate was isolated <1997SC431>. Under acidic conditions, addition of water at the double bond of 2-phenyl-3-formyl-l,4-benzodioxin 33 afford an hemiketal which recyclized. After dehydration, the 2-benzoyl-l,4-benzodioxin 34 was isolated in very good yield <2000CHE351>. 

The oxymercuration reaction of various 2-substituted 1,4-benzodioxin derivatives 35 in the presence of a suspension of mercuric acetate in water/THF followed by treatment in situ with sodium chloride and then with sodium borohydride as a reducing agent provided in excellent yields the expected hemiketals 36 (Scheme 2) <1997X2061 >. 

Dithiin, 1,4-benzodioxin, and its 2-substituted derivatives can be readly deprotonated and trapped with electrophiles although the reaction is more problematic with 1,4-dioxin. Oxanthrene and phenoxathiin are cleaved with lithium <1996CHEC-II(6)447>. A more recent example deals with the metallation at C-3 of the 1,4-benzodioxane 60 bearing a carboxylic acid function at C-2, with lithium diisopropylamide (EDA) and subsequent quench with iodomethane. The corresponding 3-methylated benzodioxane 61 was isolated in 70% yield (Equation 6) <2000EJM663>. 

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