Dioxane complexes

Sulfonation of the aromatic ring of l, 2, 2 -trifluorostyrene below 0 C does not give satisfactory yields with chlorosulfonic acid or a sulfur trioxide-dioxane complex Tar forms on heating In contrast, under similar conditions ipso substitution IS facile at the position of a trialkylsilyl or -stannyl group Thus, 4-trimethyl-silyl-T 2, 2 D-trifluorostyrene affords the corresponding trimethylsilyl sulfonate [20] (equation 9)... 

Treatment of 2,7-di-/ert-butylthiepin (1) either directly with bromine at — 78 °C, or with pyridinium bromide perbromide at room temperature, gives the thiophene compound 2. In contrast, bromination with bromine-1,4-dioxane complex or pyridinium bromide perbromide in the presence of acetic acid leads to the thiopyran derivative 3.87 To account for these results a homothiopyrylium ion has been proposed as a common intermediate, formed by electrophilic bromination at C4 in the first step. 

Equation (aj) also allows the synthesis of unsymmetrieally substituted borazines, e.g., (EtBMe2B2NjMe3)Cr(CO)3 or (PhBMe2B2N3Me3)Cr(CO)3 . The reactions take place in dioxane at 30-40°C with reduced pressure to pump off eliminated nitrile. The dioxane complexes (C4Hg02)2M2(C0)5 are intermediates. If liquid borazines are used additional solvent becomes unnecessary. 

Some common oxygen-containing solvents give isolatable Hg(I) complexes. For example, both diglyme and 1,4-dioxane form Hg2(solvent)2(N03)2 complexes. The diglyme complex forms when Hg2(N03)2 2 HjO is dissolved in diglyme containing a little CH(OEt)3 to remove HjO. The dioxane complex forms in MeOH. 

If the product is isolated in a nitrogen dry box, the filtrate is evaporated without heat until a small amount of solvent remains. The precipitate is collected cold and rinsed with cold ethyl ether. The 1 1 pentafluorophenylcopper dioxane complex is obtained with no significant loss of yield and is nearly white. 

Pentafluorophenylcopper exists as a tetramer. It forms complexes with a variety of reagents and solvents as well as ate complexes a representative list is given in Table I. For many syntheses the crude reaction mixtures of cuprous halide with either pentafluorophenylmagnesium bromide, or pentafluorophenyllithi-um, or the pentafluorophenylcopper-dioxane complex react as well as the solvent-free tetramer. 

The preeipitated chlorophyll-dioxane complex is thereafter reeovered by means of eentiifugation. The complex is dissolved in acetone to free the native chlorophylls, and the resultant solution is then decreased to a small volume under reduced pressure to provide a eoncentrated sample for chromatography. 

The first member of the new class of stable radicals, (t-Bu2MeSi)3Si 43, was synthesized by the one-electron oxidation of the silylsodium derivative (t-Bu2MeSi)3SiNa with dichlorogermylene-dioxane complex GeCl2 diox in Et20 (Scheme 2.35). ... 

Isolated as a dioxane complex, it ignites in air. See related ALKYLMETALS... 

GeCl2 can be inserted into carbon-halogen bonds upon release from its dioxane complex... 

A l,l,2,2-tetrachloro-l,2-digermacyclobutene, 113, has been obtained282 by the reaction of the dioxane complex of GeCl2 with 3,3,6,6-tetramethyl-l-thiacyclohept-4-yne ... 

Diol complexes, 9 211 d ion complexes, heavier, structure changes prior to ligand exchange, 34 258-259 Diopside, 4 61 crystal structure of, 4 51 p-Dioxane complexes, osmium, 37 312... 

Similarly, using either sulfuric acid, the SOs/dioxane complex, or a solution of SO3 in chloroform/dioxane, 4,6-diphenyl-l,2-oxathiin 2,2-dioxide was obtained from phenyl acetylene <1999RJ0415>, 3,6-disubstituted-l,2-oxathiane 2,2-dioxides were obtained from allylphenol <2002RJ01210>, and 3,4-dihydro-6-phenyl-l,2-oxathiin-4-one 2,2-oxide was obtained from Ph-CO-CH2-COMe <1991CIL253>. 

The chemistry of compounds with gold-germanium bonds has developed considerably since Schmidbaur and coworkers reported the first derivatives obtained by the insertion reaction of GeCl2 (as its dioxane complex) into a gold-halogen bond [75]. Both neutral and ionic compounds have been reported and a larger structural diversity in comparison with the silicon analogs has been established (Table 4.4). 

When the above procedures fail to give a clean product then dissolve the NaBH CN (lOg) in tetrahydrofuran (80ml) and add N MeOH/HCl until the pH is 9. Pour the solution with stirring into dioxane (250ml). The solution is filtered, and heated to reflux. A further volume of dioxane (150ml) is added slowly with swirling. The solution is cooled slowly to room temp then chilled in ice and the crystalline dioxane complex is collected, dried in a vacuum for 4h at 25°, the 4h at 80° to yield the amorphous dioxane-free powder is 6.7g with purity >98% [JACS 93 2897 797/]. The purity can be checked by iodometric titration [AC 91 4329 1969]. 

Pentafluorophenylcoppcr, 5, 504-505, m.p. 200°(dec.). Detailed directions for preparation of the reagent, which exists as the tetramer, and of the dioxane complex, have been published (equation I). The report includes use for the preparation of (pentafluorophenyl)benzene (79% yield) and l-(pentafluorophenyl)-adamantane (9.3% yield).1... 

An apparent Ga1 coordination compound, Ga(diox)2Cl, containing the 1,4-dioxane ligand was studied crystallographically some years ago.1 This system is due for reinvestigation now that the related dioxane complex of Ga2CL, has been shown not to contain Ga(diox)2, as previously supposed, but to be a molecular complex of Ga11 (Section 25.1.13.1). 

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