1,3 Dithiane, 2-phenyl

Dithiane, 2-phenyl-bond angles, 3, 949 conformation, 3, 949 structure, 3, 949 sulfoxide... 

The pA of 1,3-dithiane is 36.5 (Cs" ion pair in THF). The value for 2-phenyl-1,3-dithiane is 30.5. There are several factors which can contribute to the anion-stabilizing effect of sulfur substituents. Bond dipole effects contribute but carmot be the dominant factor because oxygen substituents do not have a comparable stabilizing effect. Polarizability of sulfur can also stabilize the carbanion. Delocalization can be described as involving 3d orbitals on sulfur or hyperconjugation with the a orbital of the C—S bond. MO calculations favor the latter interpretation. An experimental study of the rates of deprotonation of phenylthionitromethane indicates that sulfur polarizability is a major factor. Whatever the structural basis is, there is no question that thio substituents enhance... 

Stirring is continued for 2 hours at room temperature, and then methanol is added until a clear solution is obtained (ca. 10 ml. of methanol is required, and some heat is generated). When the solution has cooled, it is washed successively with 200 ml. of aqueous 2N potassium carbonate and 200 ml. of water. The aqueous phases are combined, washed with three 100-ml. portions of chloroform, and discarded. The organic phases are then combined, dried over sodium sulfate, and decolorized with activated carbon. Concentration of the chloroform solution thus obtained provides three crops of pale yellow crystals, which are washed with 30% hexane in chloroform and dried for 2 hours at 80°/0.1 mm. The total yield of 3-(2-phenyl-l,3-dithian-2-yl)indole is 22.3-25.4 g. (72-81%), m.p. 167-169° (Note 7). This material requires no further purification for use in Parts D or E. 

L//-Indole, 3<2-phenyl-l, 3-dithian-2-yl), 10 Indoles, 34 Indoles, 3-acyl-, 8 Indoles, 3 -alkyl, 8 Isocyanate, chlorosulfonyl [Sulfuryl chlonde isocyanate], 41 Isocyanate,2-propyl- [Propane, 2-iso-cyanato-], 96... 

ABSTRACT Zeolite Y modified with chiral sulfoxides has been foimd catal rtically to dehydrate racemic butan-2-ol enantioselectively depending on the chiral modifier used. Zeolite Y modified with R-l,3-dithiane-1-oxide shows a higher selectivity towards conversion of S-butan-2-ol and the zeolite modified with S-2-phenyl-3-dithiane-1-oxide reacts preferentially with R-butan-2-ol. Zeolite Y modified with dithiane oxide demonstrates a significantly higher catalsdic activity when compared to the unmodified zeolite. Computational simulations are described and a model for the catalytic site is discussed. 

Zeohte Y modified with R-l,3-dithiane-1-oxide/ S-2-phenyl-l,3-dithianeoxide Total conversion of R- and S-butan-2-ol Relative ratio of preferential enantiomeric reaction of R- and S-butan-2-ol... 

Fig. 3 Calculated low energy conformation of the protonated dithiane oxide cation (R=phenyl) in zeolite Y (Si/Al = 1). The views and presentational details are as for figure 2.

Bohman and Allenmark resolved a series of sulphoxide derivatives of unsaturated malonic acids of the general structure 228. The classical method of resolution via formation of diastereoisomeric salts with cinchonine and quinine has also been used by Kapovits and coworkers " to resolve sulphoxides 229, 230, 231 and 232 which are precursors of chiral sulphuranes. Miko/ajczyk and his coworkers achieved optical resolution of sulphoxide 233 by utilizing the phosphonic acid moiety for salt formation with quinine. The racemic sulphinylacetic acid 234, which has a second centre of chirality on the a-carbon atom, was resolved into pure diastereoisomers by Holmberg. Racemic 2-hydroxy- and 4-hydroxyphenyl alkyl sulphoxides were separated via the diastereoisomeric 2- or 4-(tetra-0-acetyl-D-glucopyranosyloxy)phenyl alkyl sulphoxides 235. The optically active sulphoxides were recovered from the isolated diastereoisomers 235 by deacetylation with base and cleavage of the acetal. Racemic 1,3-dithian-l-oxide 236... 

Some cyclic thioacetals have an A-SE2 hydrolysis mechanism,206 as do some 2-aryl-2-methyl-l,3-dithianes, except for the 4-NO2 derivative, which looks more A2-like.207 In 10 vol% dioxane/aqueous HC104 mixtures, reactive 2-aryl-2-phenyl-l,3-dithianes are believed to have an A-SE2 hydrolysis mechanism, whereas the least reactive ones have an A2 mechanism.130 Isothiocyanates are believed to hydrolyze by a mechanism that involves simultaneous proton transfer to nitrogen and attack of water at carbon in a cyclic transition... 

Figure 25. Schematic illustrating the continuous flow synthesis of 2-phenyl-l,3-dithiane [41],...

Exclusive C-2 lithiation was also observed in the case of the 1-ben-zenesulfonyl-3-(l,3-dithian-2-yl) derivative, but when an excess of/j-BuLi was employed, in an attempt to promote deprotonation in the dithiane ring, ortho-lithiation of the phenyl substituent was observed forming instead (Scheme 18) (9IT79I1). 

The synthesis of 2-substituted-l, 3-dithiane-l -sulfimides using T-( -tolylsulfonyl)imino(phenyl)iodinane (TsN=IPh) and a catalytic amount of Cu(OTf)2-box was reported to proceed with good yields (57-70%) and diastereoselectivity (trans xis 96 4-100 0). However, the ee was low (32 0%) (Equation 42) <1998J(P1)2373>. 

Like many other 1,3-dipoles (e.g., nitrile ylides, imines, and oxides) (7), thiocarbonyl ylides undergo head-to-head dimerization to give sterically crowded 1,4-dithianes. The first reported example involves the formation of 2,2,3,3-tetraphenyl-l,4-dithiane (18) from thiobenzophenone (5)-methylide (16) (17,28) (cf. Scheme 5.3). Other (5)-methylides are known to form analogous 1,4-dithianes (e.g., thiofluorenone (5)-methylide yields 172) (17). The (5)-methylides of 4,4-dimethyl-2-phenyl-l,3-thiazole-5(4//)-thione (105) and methyl dithiobenzoate (60,104) dimerize to give compounds 173 and 174, respectively. 

Li-CH-(S ) 1 C0-N(CH3)2 Ar 0 1 II 02N CH2-CH-CH-C-NfCH3)2 s- s 3- (2,5-Dimethoxy-4-methyl-phenyl)-2-( 1,3-dithian-2-yl) -4-nitro-butansdure-dimethyl-amid 88 137-138... 

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