Sulfones, vinyl selectivity

Okada et al. [93] have reported water transport numbers based on a measurement of the potential developed when a differential pressure is applied across a membrane contacting dilute electrolytes. For a crosslinked, sulfonated vinyl copolymer, cation-selective membrane designated CR61 AZL 386, they report a water transference number of 2.3 for the protonic form of the immersed membrane. 

Perhydroindans (46) and (47) could be obtained in 73% yield from the carbonate (48) with only minor amounts of elimination product. The use of BSA and the triisopropyl phosphite-palladium acetate catalytic system provides further improvement. The low cisitrans selectivity in the formation of the first ring, and rapid subsequent cyclization account for the fact that the ratio of (46) to (47) is only 2 1 (Scheme 2.14). Even the presence of a bulky trialkylsiloxyl substituent adjacent to the vinyl sulfone moiety has only a minor influence on the cisitrans selectivity [24]. 

Cycloadditions of the 1,3-dipolar nitrile oxides and diazoalkenes to acyclic vinyl sulfones are in general highly selective, the particular regioisomer formed depending on the substituents of both reactants213,214. Nitrones, on the other hand, tend to yield mixtures of the two possible isomers (see equation 78). 

Unfortunately, it quickly became apparent that a shortfall in this proposal was an inability to prepare the desired vinyl halide 25 in a straightforward and selective manner [19]. In contrast, we reasoned that the selective formation of an enol sulfonate, such as the enol triflate 26a, could be controlled by judicious tuning of enolization conditions starting from the corresponding ketone, and that such an enol sulfonate would possibly be a substrate for a palladium-mediated coupling (Scheme 9.17). In this way a common intermediate from the previously defined synthesis, that is, the racemic ketone rac-13 or its cyano equivalent rac-5 could be used to generate the required enamide. 

Selenosulfonylation of olefins in the presence of boron trifluoride etherate produces chiefly or exclusively M products arising from a stereospecific anti addition, from which vinyl sulfones can be obtained by stereospecific oxidation-elimination with m-chloroper-benzoic acid134. When the reaction is carried out on conjugated dienes, with the exception of isoprene, M 1,2-addition products are generally formed selectively from which, through the above-reported oxidation-elimination procedure, 2-(phenylsulfonyl)-l,3-dienes may be prepared (equation 123)135. Interestingly, the selenosulfonylation of butadiene gives quantitatively the 1,4-adduct at room temperature, but selectively 1,2-adducts at 0°C. Furthermore, while the addition to cyclic 1,3-dienes, such as cyclohexadiene and cycloheptadiene, is completely anti stereospecific, the addition to 2,4-hexadienes is nonstereospecific and affords mixtures of erythro and threo isomers. For both (E,E)- and ( ,Z)-2,4-hexadienes, the threo isomer prevails if the reaction is carried out at room temperature. 

The stereochemical outcome for addition of r-l,3-dioxolan-4-yl and oxiranyl radicals to phenyl vinyl sulfone has been probed. The results indicated that the symanti selectivity could be altered by changing the group next to the radical in the diox-olanyl case but not in the oxiranyl case (bulky groups had a large xyn-directing effect) (Scheme 39). Several alkenyl-lactones and -lactams have been subjected to hydrosilylation conditions using carbohydrate-derived thiols as homochiral polarity reversal catalysts (yields 25-96% ee 5-95%) " ... 

With aldehyde donors, the reactions are generally syn selective. A range of acceptors can be used, including a,p-unsaturated nitro compounds [72, 270, 274-281], a,p-unsaturated ketones [71, 282-285], vinyl phosphonates [286] and vinyl sulfones [287] etc. (Scheme 27). So far, no general anti selective... 

The structure of the benzoate derivative 166 was established by X-ray analysis, confirming the selective oxidation of the sulfur atom at the 6-position of thieno[2,3- ]thiophene-2-sulfonamides. The activated double bond of the cyclic vinyl sulfone moiety readily underwent nucleophilic addition, which was exemplified by reaction of 165 with 4-methoxybenzylthiol in the presence of base to provide a mixture of 167 and 168 <1999JHC249>. 

Table 6.13 Selected examples of the epoxidation of vinyl sulfones.

Materials. Epoxy novolac, DEN-431, obtained from Dow Chemical Co. was selected as the epoxy component. A 3,3 -diazidodiphenyl sulfone synthesized in our laboratory (5) was used as the azide compound. Poly(/7-vinyl phenol) obtained from Maruzen Oil Co. was used as the phenolic resin matrix. The coating solvent was cyclohexanone. The developer used in this study was 0.1 N tetramethylammonium hydroxide aqueous solution. 

Styrene and Vinyl Monomer, Polymer, and Copolymer Sulfonates. The incorporation of sulfonates into polymeric material can occur either after polymerization or at the monomer stage. The sulfonic acid group is strongly acidic and can therefore be used to functionalize the polymer backbone to the desired degree. The ability of sulfonic acids to exchange counterions has made these polymers prominent in industrial water treatment applications, separators in electrochemical cells, and selective membranes of many types. 

Y. Benmakroha, I. Christie, M. Desai and P. Vadgama, Poly(vinyl chloride), polysulfone and sulfonated polyether-ether sulfone composite membranes for glucose and hydrogen peroxide perm-selectivity in amperometric biosensors, Analyst, 121 (1996) 521-526. 

Supercritical carbon dioxide with a minute co-solvent addition is an effective medium for the 1,3-dipolar cycloaddition of azomethine ylides with DMAD to produce substituted pyrroles.67 The 1,3-dipolar cycloaddition of nitrile ylides [e.g. benzonitrile (4-nitrobenzylide) and 4-nitrobenzonitrile(benzylide)] with acrylamides provided a synthesis of 3,4-dihydro-2//-pyrroles with moderate to good yields.68 The Pt(II)-or Au(III)-catalysed 3 + 2-cycloaddition of the transition metal-containing azomethine ylide (63) with electron-rich alkenes provided a carbene complex (64), which yields tricyclic indoles (65) having a substituent at 3-position (Scheme 17).69 The 1,3-dipolar cycloadditions of azomethine ylides with aryl vinyl sulfones are catalysed by Cu(MeCN)4C104-Taniaphos with nearly complete exo- selectivity and enantioselec-tivities up to 85% ee.10 The 3 + 2-cycloaddition of benzol/>]thiophene 1,1-dioxide... 

Since the cis- and trans-vinyl radicals can equilibrate at this stage and the trcms-radical is the more stable of the two, both diastereomeric acetoxy sulfones would still lead selectively to the same product. 

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