Sulfone, seven-membered

Mullins71 have shown that the seven-membered cyclic sulfone (38) can be converted photochemically at 254 nm, as well as by thermolysis, into a mixture of 39 and 40. Interestingly, in this series, compound 40, the result of hydrogen transfer (disproportionation) in the presumed intermediate biradical, remained the major product when different solvents and different wavelengths were employed for the irradiation. 

Sulfenoetherification. The reagent in combination with trifluoromethane-sulfonic acid converts suitably unsaturated alcohols into five- to seven-membered cyclic ethers. The cyclization is considered to involve an intermediate episulfonium ion. 

Axially chiral phosphoric acid 3 was chosen as a potential catalyst due to its unique characteristics (Fig. 2). (1) The phosphorus atom and its optically active ligand form a seven-membered ring which prevents free rotation around the P-0 bond and therefore fixes the conformation of Brpnsted acid 3. This structural feature cannot be found in analogous carboxylic or sulfonic acids. (2) Phosphate 3 with the appropriate acid ity should activate potential substrates via protonation and hence increase their electrophilicity. Subsequent attack of a nucleophile and related processes could result in the formation of enantioenriched products via steren-chemical communication between the cationic protonated substrate and the chiral phosphate anion. (3) Since the phosphoryl oxygen atom of Brpnsted acid 3 provides an additional Lewis basic site, chiral BINOL phosphate 3 might act as bifunctional catalyst. 

Thiete sulfones show an irregular behavior pattern when involved in cycloaddition reactions. With 1,3-dienes, dienamines, enamines, ynamines, diazoalkenes, cyclopropadiene, and its substitution products, furan, and anthracene, the addition proceeds in the normal fashion. With certain Diels-Alder reagents such as tetraphenylcyclopentadienone (tetracycloneX however, the cyclic sulfones react anomalously. The Diels-Alder adducts undergo decomposition with SO 2 and CO extrusion to a seven-membered ring, the tetraphenylcycloheptatriene 223. Bicyclic octadienone is produced as well (Eq. 62). The mechanism of this unusual reaction is proposed by... 

Nitrones can be generated by Michael reaction of oximes with appropriate conjugated substrates.25 If a generated nitrone has a built-in dipolarophile, cyclization can ensue (Scheme 15). There are three synthetic variations on this theme.25a,b First, the oxime may contain the dipolarophile as in (56). Reaction of (56) with phenyl vinyl sulfone provided a quantitative yield of the tandem product as one stereoisomer. Alternatively, die dipolarophile can reside in the Michael substrate as in (57). Reaction of (57) with cyclohexanone oxime produced two isoxazolidines from competitive cyclization of the intermediate nitrone through six- and seven-membered carbocyclic transition states. It is also possible to carry out an intramolecular Michael addition followed by an intramolecular nitrone cyclization as in thermolysis of (58) to produce a tricyclic isoxazolidine. Very recently several examples of a tandem Diels-Alder, Michael addition, nitrone cyclization sequence have been reported.250... 

The symmetrical seven-membered sulfone, 11 (Table I), has been reported by Kim to show high in vitro potency (IC50 = 1 nM), good antiviral activity in cell culture (EC90 = 20 nJM), and excellent pharma-... 

On the action of base (Na0H-H20 or EtsN-CHCls), five- and seven-membered )3-epoxysulphones lead to 7-hydroxy-a,i3-unsaturated sulfones. In the case of a-hydroxyalkyloxiranes, base causes reversible oxirane migration (Payne rearrangement) (Eq. 114). Such an isomerization has also been observed in sugar chemistry in response to sodium methylate (e.g., Eq. 115). °... 

Ring closure to three, five, six and seven membered rings by Michael Initiated Ring Closure (MIRC) especially of sulfones, stereoselective for (3+2) cycloadditions. 

It is possible to abstract a proton from a 2-alkylated-1,3-dithiane and perform a second alkylation reaction. If the 2-alkylated-1,3-dithiane is prepared from the aldehyde with propane-1,3-dithiol, then after alkylation and hydrolysis the sequence provides a method for converting an aldehyde into a ketone. Starting with the commercially available 1,3-dithiane, an alkyl halide or sulfonate can be converted into the homologous aldehyde. Two alkyl groups can actually be introduced successively without isolation of the intermediates and this has been applied to the synthesis of three- to seven-membered cyclic ketones. 

Cycloaddition of allyl cations to conjugated dienes provides a route to seven-membered carbocycles. One of several methods can be used to generate the allyl cation, such as from an allyl halide and silver trifluoroacetate, or from an allyl alcohol by way of its trifluoroacetate or sulfonate. Cycloaddition of the allyl cation proceeds best with a cyclic diene, particularly for intermolecular reactions. Thus, cyclohexadiene and methylallyl cation gave the bicyclo[3.2.2]nonadiene 187 (3.125). Many intramolecular examples are known, such as the formation of the... 

The presence of sulfur and adjacent oxygen in the seven-membered ring, 1,2-oxathiepine, makes these compounds unstable therefore, most of the known ring systems possessing this moiety are obtained in the form of the 5-oxide (sulfonate) or 5,5-dioxide (sulfonate). 

In 2008, the Katsuki group reported a highly enantioselective oxidation of cyclic sulfides using the (salalen)Al complex 33 as the catalyst (Scheme 19.41).Oxidations of six-membered cyclic sulfides, thiochroman-4-ones, furnished the corresponding sulfoxides in high yield with excellent enantioselectivities. Five-membered cyclic sulfide and seven-membered cyclic sulfide were also good substrates for the aluminium-catalysed system. In these oxidations, over-oxidation of sulfoxides was observed, and the corresponding sulfones were obtained in 5-20%. 

In a related study, the annulation is combined with a ring expansion reaction. The reaction utilizes a -keto sulfone as the two-carbon component along with an allylic mesylate as the bifunctional reagent. The alkylation/cyclization process is outlined in eq 4. The subsequent ring expansion appears to be a general process except for cases involving fused six- and seven-membered ring systems (eq 5). 

Benzannulation of the seven-membered ring in 37 and 39 leads to 42-44, as shown in Figure 4.12. Unlike 1,2-benzannulated pleiadiene (42), which is a stable compound [44, 45], 2,3-benzannulated derivatives 43 and 44 were reported by Cava and Schlessinger in 1963 as reactive species that appeared not isolable [46] because they both contain an unstable o-quinodimethane moiety. Pyrolysis of cyclic sulfone 45 at 210 °C in the presence of AT-phenylmaleimide gave the adduct 46 in 70% yield, and resulted in the dimer 47 in 51% yield under similar conditions in the absence of a dienophile, as shown in Scheme 4.10a. These reactions suggest... 

Diphenylethane 22 is more reactive towards chlorosulfonic acid than diphenyl-methane 18, probably as a result of increased hyperconjugative electron release from the ethylene bridge bond. When diphenylethane 22 was heated with a large excess of chlorosulfonic acid (20 equivalents) at 100 °C (4 hours), the cyclized product 24 was isolated in excellent (90%) yield (Equation 8). The cyclization to the seven-membered ring sulfone 24 was more easily achieved than the analogous conversion of diphenylmethane 18 to the six-membered ring sulfone 21... 

Trifluoromethane sulfonic acid was also used as a catalyst in ring-opening copolymerization of a seven-membered cyclic carbonate and trioxane. However, the carbonate monomer was consumed faster than trioxane and the decarboxylation took place to afford corresponding polyacetal-PC type copolymers containing poly(oxytetramethylene) units. 

Sultones are the internal esters of hydroxy sulfonic acids and are the sulfur analogs of lactones. Sultones are demanded scaffolds in medicinal chemistry research. Biological studies on sultones are mainly concerned with their toxicological, skin sensitization, and antiviral activities [20]. Sultones are synthetically useful heterocycles which can react with a variety of compounds to introduce the alkylsulfonic acid function and therefore used as sulfoalkylating agents [21]. There have been several new developments for the synthesis of sultones which have also been applied in the total synthesis of natural products. In recent years, the palladium-catalyzed direct arylation of several aromatics via a C-H bond activation using aryl halides has led to successes. An intramolecular version of this reaction has allowed the synthesis of several biaryls via the formation of five- to seven-membered rings. Thus, the sultones should be synthesized by C-H activation via two pathways (Scheme 4.14). 

Several carbon-hydrogen bond substitutions are involved in the palladium-catalysed reaction of arylsulfonic acids with arenes to yield aromatic sulfones. A plausible mechanism, shown in Scheme 9, involves the initial formation of the palladacycle (99) which, after eoupling with the arene, yields the biphenyl derivative (100). Further coordination and carbon-hydrogen activation gives the seven-membered palladacycle (101) that affords the sulfone, (102), after reductive elimination. ... 

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