1,3-Thioxanes

Thioxanes (60) give similar ring-opening reactions but the subsequent reaction to lose oxygen is not observed.1,3-Dithiolanes such as the cis and trans forms of (61) can be isomerized by Lewis acids but fail to undergo reduction with H2AICI this may be a consequence of solubility problems. 

Borane—dimethyl sulfide complex (BMS) (2) is free of these inconveniences. The complex is a pure 1 1 adduct, ca 10 Af in BH, stable indefinitely at room temperature and soluble in ethers, dichioromethane, benzene, and other solvents (56,57). Its disadvantage is the unpleasant smell of dimethyl sulfide, which is volatile and water insoluble. Borane—1,4-thioxane complex (3), which is also a pure 1 1 adduct, ca 8 Af in BH, shows solubiUty characteristics similar to BMS (58). 1,4-Thioxane [15980-15-1] is slightly soluble in water and can be separated from the hydroboration products by extraction into water. 

The structures of the cis- and frans-isomers of Pt(l,4-thioxane)2Cl2 have been determined. The Pt—S distance (2.298 A) is longer in the frans-isomer than in the cis-form (2.273 A) showing the frans-influence of thioxane to be greater than that of chloride [119],... 

The 4 1 complex has square planar coordination of platinum (Pt-S 2.317— 2.321 A) similar bond lengths are found in the corresponding complex with 1,4-thioxane [120]. Complexes with thiourea are important in Kurnakov s test (section 3.8.2) Pdtu4Cl2 has square planar coordination (Pd—S 2.33 A). 

Figure 9 Adducts of dimethylzinc with (a) trimethyltriazine (b) 1,4-dioxan (c) 1,4-thioxan.

Also dipropyl sulfoxide [LnBra (161)], diphenyl sulfoxide [Lnl3 (155)], tetramethylene sulfoxide [LnCl3 (162), LnBrs (163), Lnls (164)], and thioxane oxide [LnCl3 (166), LnBrs (163), Lnl3 (266)]. 

Hexafluorophosphate derivatives, such as [M(Me2SO)n][PF6]3 (M = La, Lu, Y), have been synthesized (365), and infrared data show O-bonding of the sulfoxide with ionic hexafluorophosphate groups. Analytical data are incomplete for this series, as decomposition, postulated to be to lanthanide fluorides, occurs. The (CH2)4SO complexes [M( CH2 4SO)t.5][PF6]3 are reported (145), which are 3 1 electrolytes with uncoordinated anions, implying a possible semibridged structure, as previously mentioned. Complexes of other cyclic sulfoxides, including thioxane oxide (146) and trans-1,4-dithiane-1,4-dioxide (147) derivatives of hexafluorophosphate salts have also been prepared. 

In addition to these systematic studies of lanthanide sulfoxide complexes, with variation in both sulfoxide and anion, other more isolated reports are available. Lanthanide isothiocyanate complexes of the cyclic sulfoxides thioxane oxide (490) and tetramethylene sulfoxide (493) have been synthesized and complexes of the unusual potentially chelating ligand 2-(ethylsulfinyl)pyridine-V-oxide (63) described. Detailed studies of the solvation of lanthanide-shift reagents by Me2SO have also appeared (178,179). 

Finally, mention should be made of the striking conformational preference of trans 2,3- and tram 2,5-dioxanes, dithianes, and thioxanes. Each of these compounds exists in a chair conformation with two diaxial halogens334- 341 ... 

Fig. 11.6 Conversion of one enantiomer to the other by CPL. The molecule 12-(9 H-thioxan-thene-9 -ylidene)-l 2H-benzo[a]xanthene exists in one of two chiral forms that can be intercon-...

Chlorprothixene Chlorprothixene, 2-chloro-9[(l-dimethylamino)-3-propyliden]thioxan-thene (6.2.7), has been proposed to synthesize starting from 2-chlorothixantone (6.2.3). The initial 2-chlorothixantone (6.2.3) is prepared from 2-mercaptobenzoic acid, the reaction of... 

Oxidation of 1,4-thioxane by BTSP and f-butyl(trimethylsilyl) peroxide in CHCI3 at 25 °C is compared to those of the same substrate by the more common oxidants, f-butyl hydroperoxide and di-f-butyl peroxide, in the same solvent. The two silyl peroxides give similar oxidations rates, which are over 50 times higher than that measured for f-BuOOH, while f-Bu202 is almost unreactive under the conditions adopted. Oxidation... 

TABLE 14. Oxidation rates of thioxane and Af,Af-dimethyl- ci-anisidine by silyl peroxides as compared to analogous carbon peroxide... 

Thiophene, dioxirane oxidation, 1156 Thiourea, dialkyl peroxide synthesis, 706 1,4-Thioxane, oxidation, 805-6 Thiyl radicals, triplet oxygen domino reactions, 221-3, 224, 225, 226 THPO (1,2,3,4-tetrahydronaphthyl hydroperoxide), 331-2 Thromboxanes, from arachidonic hydroperoxides, 612... 

Trimerization of aldehydes affords trialkyl-1,3,5-thioxanes 11. Compounds of this type were obtained from acetaldehyde, propionaldehyde (29,33), isobutyraldehyde (47), and isovaleralde-hyde (35). The two isomers normally formed can be separated by GC. 

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