Oxathiane

When a mixture of p-anisaldehyde and dimethyl sulfone was treated with excess potassium t-butoxide in DMF at 60-65 °C, bis-unsaturated sulfone 277 was obtained. In the reaction at 50 °C using a small amount of base, the main product was a heterocyclic compound, i.e., 2,4-di-p-methoxyphenyl-1,4-oxathiane 4,4-dioxide 278 . 

AgL(hfac)] (L = SMe2, SEt2, SPr2, SBu2, 1,4-oxathiane).811 The use of aerosol vaporization methods has allowed efficient CVD from complexes [Ag(hfac)(SR2)].819... 

MRH values for 20 combinations with oxidisable materials are given. 1,4-Oxathiane... 

Benzyltriethylammonium tetrathiomolybdate, [BnNEt3]2MoS4, is a useful sulfur transfer reagent which has now been shown to effect a one-pot, three-step sequence of S-transfer— reduction—Michael addition. The intramolecular version successfully produces 1,4-oxathianes from the bromoenone 108 (Scheme 65). In like manner, the bicyclo[3.3.1]nonane skeleton incorporating a thiopyran ring can be constructed . 

Oxathianes Dehydration of 2,2 -bis(hydroxyethyl) sulfides with (C6H5),P(OC2H5)2 provides a stereoselective route to 1,4-oxathianes in moderate (isolated) yields. 

S)-Ethyl-6-methyl-1,4-oxathian-2-one 2,4,6-trinitrobenzenesulfonate S J. Chem. Soc., Chem. Commun. 1975,629... 

Saturated rings like 1,4-dioxane 16, frequently used as a solvent, 1,4-dithiane 17, and 1,4-oxathiane 18 were first prepared at the turn of the twentieth century. 

One of the main research interests in this area is to find new oxidizing agents having the highest chemoselectivity to obtain the sulfoxide derivatives without overoxidation to sulfones. 1,4-Oxathiane 18 was often used as a model sulfur-containing compound to afford 82 (Table 2) and 17 similarly gave 83. m-2,6-Dimethyl-l,4-dithiane was oxidized to the... 

Moreover, the sulfur atom of 1,4-oxathianes can be alkylated. Thus, reaction of 3-aryl-l,4-oxathianes 84 with (trimethylsilyl)methyl trifluoromethanesulfonate gave a mixture of cis- and /ra t-isomers of 3-aryl-4-(trimethylsilyl)-methyl-l,4-oxathianium triflates 85 (Equation 12) <1997J(P1)715>. 

Chiral bis-lithium amide bases have been used for enantiotopic deprotonation of the sulfonium salt of 1,4-oxathiane 86. The anion undergoes an enantioselective thia-Sommelet rearrangement to afford the 3-substituted-1,4-oxathiane 87. Only bis-lithium amide bases were effective, giving products with high diastereoselectivity and with low to moderate enantioselectivity (Equation 13) <2003TL8203>. 

The desulfurization of 1,4-oxathiane with sodium in refluxing hydrocarbon solvent, which allows the formation of diethyl ether in very good yield (>95%), can be reported here <1998TL2671>. Furthermore, 6-hydroxy-1,4-benzodithiin undergoes a reductive cleavage with lithium in liquid ammonia, provided the 3,4-dimercaptophenol <2004BML3753>. 

In a similar way, 1,4-oxathian-2-one and l,4-dioxan-2-one were obtained from the condensation of thioglycolic acid and glycolic acid, respectively <1979J(P1)1893, 1998T11445>, and from palladium-catalyzed <1999JOC6750> or oxoammonium salt <2004JOC5116> oxidations of 2,2 -thiodiethanol or diethylene glycol. Asymmetric syntheses... 

Taking advantage of a tandem sulfoxide elimination-sulfenic acid addition approach to cyclic sulfoxides <1977J(P1)1574>, the synthesis of a number of novel 1,4-oxathiane oxides 229 and 230 based on the intramolecular addition of sulfenic acids to alkenes or alkynes tethered through an ether linkage has been reported (Equation 38) <20050BC404>. 

Synthesis of 2,3-dihydro-l,4-dithiin 11 was accomplished from l,3-dithiol-2-one 247 in the presence of dibro-moethane and potassium hydroxide <1998JOG3952>, while reaction of 2,3-dichloro-l,4-dioxane with powdered Zn in hexamethylphosphoramide (HMPA) was used for the synthesis of 1,4-dioxene 10 <1998JPP10067773>. To obtain substituted 1,4-oxathianes, the hydrogenation of the corresponding partially saturated compounds has been employed <2001J(P1)2604>. 

Furthermore, 1,3-oxathiolanes 255 are efficiently converted, via sulfur ylide intermediates, to 1,4-oxathianes 256 and 257 by ring expansion with a silylated diazoacetate in the presence of copper catalyst (Scheme 27) <2002GC346, 2005T43>. 

Six-membered non-aromatic heterocycles containing more than one heteroatom Morpholines, 1,4-dioxanes, 1,4-oxathianes Six-membered aromatic heterocycles containing one heteroatom Pyridine... 

The sulfoxide that has been studied was obtained by the oxidation of a sulfide, namely, (2S,6K)-6-(hydroxymethyl)-2-methoxy-1,4-oxathiane,47 synthesized from methyl 6-O-trityl-a-D-glucopyrano-... 

Oxathiane has only been fluorinated84 over potassium tetrafluorocobaltate(III) (vide infra). and this gives products very similar in structure to those formed in the dioxane/cobalt(Hl) fluoride fluorination. 

Hydroboration. This complex of borane is more reactive than borane-dimethyl sulfide (4, 124, 191 5, 47) and has the added advantage that after hydroboration, 1,4-oxathiane can be removed easily as the water-soluble sulfoxide. 

Routes to benzo-fused derivatives of 1,4-dioxanes, 1,4-oxathianes and 1,4-dithianes make use of anions or dianions of the appropriate 1,2-disubstituted benzene. An alternative approach to the synthesis of 1,4-benzodioxanes involves Diels-Alder addition reactions of alkenes across the quinone function of 1,2-benzoquinones, e.g. (352) — (353). 

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