1,4-Benzodioxin

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... 

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>. 

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. 

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 . 

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>. 

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>. 

Linear annulated dioxins synthesis were reported by analogy with that of the 1,4-benzodioxin series <2002T1533> or in a modification of the Ullmann ether synthesis <2004T8899>. 

As already mentioned in CHEC-II(1996), 1,4-benzodioxins are often obtained from the corresponding dihydro compounds <1996CHEC-II(6)447>. Thus, elimination reactions of monoiodo and monobromo <2001HC0135> or dibromo benzodioxanes <2000EJM663> allow the formation of various 2-substituted-l,4-benzodioxins in good yields. 6-Methyl-l,4-benzoxathiin was prepared from the saturated derivatives by reaction with SOCI2, then quinoline <2003BML2083>. 

Dihydro-5//-1,4-benzodioxepin (408) and halogenated derivatives (407) and (409) are obtained from 1,4-benzodioxin (406) by dihalogencarbene addition, thermolysis, and reduction (83AG(E)64). 

The identical vicinal coupling constants for 1,4-benzodioxin and 2,3-dihydro-l,4-dioxin, 3.73 Hz, have been cited as evidence to confirm the absence of aromatic character in the former (67AJC1773), and by the same reasoning (22) should also be non-aromatic (70ZC296). The corollary of this argument, however, is that the dissimilar 3/ values for 1,4-dithiin, 6.97 Hz, and its dihydro analogue, 10.02 Hz, indicate substantial aromatic character in the former. However, it has been pointed out that this simple type of comparison fails to allow... 

Pentafluorophenoxy)ethanol (24) reacts with potassium hydroxide to give 5,6,7,8-tetra-fluoro-2,3-dihydro-1,4-benzodioxin (25).134,135... 

Benzodioxines. The reaction of benzo-l,4-dioxanes with NBS catalyzed by dibenzoyl peroxide results in 2,3-dibromo derivatives, which undergo denomination to benzo-l,4-dioxines when treated with sodium iodide in acetone (equation I).1... 

Substituted 1,4-benzodioxins yield the 7-aryl compound exclusively under Friedel-Crafts conditions, but the 2,3-dihydro derivatives give a mixture of the 6- and 7- isomers in which the latter predominates (95T2619). The reaction of the tetraoxabicyclo-[4.4.0]decanes with allyltrimethylsilane provides good yields of... 

RN 2165-19-7 MF C10H,3N3O2 MW 207.23 ON ((2,3-dihydro-1, 4-benzodioxin-2-yl)methyl]guanidine... 

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