Sulfones cleavage

Compounds 45 exhibit, in addition to sulfone-sulfinate rearrangements " ", alkyl sulfone cleavages , intramolecular Smiles-type rearrangements and extrusion of SOj , an exceptional mode of remote group interaction which leads to the loss of... 

For a list of reagents used for sulfonate cleavages, with references, see Ref. 144, pp. 153-154. 

Synthesis of Oxindoles Using Samarium(II) Iodide for Sulfone Cleavage. a-Sulfanyl-A-aryl acetamide attached to resin via the sulfur atom 134 undergoes efficient Pummerer cyclization upon activation of sulfur group to yield oxindole derivatives 135 (Scheme 12.30). Oxidation of 135 to sulfone 136 using Oxone followed by alkylation yielded the alkylated sulfone 137, which was then cleaved from the resin in a traceless manner using samarium(ll) iodide to yield the heterocyclic product 138. 

Synthesis of Butenolides/Butyroactones Using Mg/HgClx for Sulfone Cleavage. Sheng et al. have reported the synthesis of butenolides and butyroactones using the sulfone-bound resin 140 (Scheme 12.31)." ° The procedure for the synthesis of butenolides/butyroactones involved the 5-alkylation of lithiophenylsulhnate resin 79, followed by sulfonyl anion alkylation with an epoxide to yield 45. Subsequent acylation... 

Synthesis of Isoxazolocyclobutanones and Isoxazolinacyclobutenones Using Swern Oxidation for Sulfone Cleavage. Resin-bound lithium benzenesulfinate 79 has also been applied in the synthesis of isoxazolocyclobutanones and isoxazolinacyclobutenones (Scheme 12.32)." Resin 79 was first converted to the polymer-supported 3-vinylcyclobutanol... 

Sulfinic acids from sulfones Cleavage of disulfones... 

Sulfoxides in general are first of all multifunctional linkers because of their possible over reaction to the corresponding sulfones and the resulting possibilities of sulfone cleavage. Additionally, the sulfoxide linker 502 can release primary alcohols 503, aldehydes 504 and alkene derivatives 505 without fur-... 

Attempts to prepare the diprOpylamino-5-sulfonic acid by sulfonation in oleum failed (385). With 2-piperidino-4-methylthiazole Ochiai reports cleavage of the 2-piperidino ring (391). 

Substitution Reactions on Side Chains. Because the benzyl carbon is the most reactive site on the propanoid side chain, many substitution reactions occur at this position. Typically, substitution reactions occur by attack of a nucleophilic reagent on a benzyl carbon present in the form of a carbonium ion or a methine group in a quinonemethide stmeture. In a reversal of the ether cleavage reactions described, benzyl alcohols and ethers may be transformed to alkyl or aryl ethers by acid-catalyzed etherifications or transetherifications with alcohol or phenol. The conversion of a benzyl alcohol or ether to a sulfonic acid group is among the most important side chain modification reactions because it is essential to the solubilization of lignin in the sulfite pulping process (17). 

An asymmetric synthesis of estrone begins with an asymmetric Michael addition of lithium enolate (178) to the scalemic sulfoxide (179). Direct treatment of the cmde Michael adduct with y /i7-chloroperbenzoic acid to oxidize the sulfoxide to a sulfone, followed by reductive removal of the bromine affords (180, X = a and PH R = H) in over 90% yield. Similarly to the conversion of (175) to (176), base-catalyzed epimerization of (180) produces an 85% isolated yield of (181, X = /5H R = H). C8 and C14 of (181) have the same relative and absolute stereochemistry as that of the naturally occurring steroids. Methylation of (181) provides (182). A (CH2)2CuLi-induced reductive cleavage of sulfone (182) followed by stereoselective alkylation of the resultant enolate with an allyl bromide yields (183). Ozonolysis of (183) produces (184) (wherein the aldehydric oxygen is by isopropyUdene) in 68% yield. Compound (184) is the optically active form of Ziegler s intermediate (176), and is converted to (+)-estrone in 6.3% overall yield and >95% enantiomeric excess (200). 

The cleavage products of several sulfonates are utilized on an industrial scale (Fig. 3). The fusion of aromatic sulfonates with sodium hydroxide [1310-73-2J and other caustic alkalies produces phenohc salts (see Alkylphenols Phenol). Chlorinated aromatics are produced by treatment of an aromatic sulfonate with hydrochloric acid and sodium chlorate [7775-09-9J. Nitriles (qv) (see Supplement) can be produced by reaction of a sulfonate with a cyanide salt. Arenesulfonates can be converted to amines with the use of ammonia. This transformation is also rather facile using mono- and dialkylamines. 

Fig. 3. Cleavage reactions of sulfonates where Ar is an aryl group.

Various processes have been disclosed wherein moist soHd sodium pyrosulfite [7681-57-4] is stirred in a steam-heated vessel with sodium carbonate. The exothermic reaction at 80—110°C results in the drying of the product. A lower grade of sodium sulfite is produced commercially in the United States as a by-product of the sulfonation—caustic cleavage route to resorcinol (333). 

This sulfonate is prepared by reaction with the sulfonyl chloride. Cleavage occurs with 0.05 MNaOH (acetone, H2O, 25°, 5 min, 83-93% yield). Here also cleavage is facilitated by intramolecular participation through the hydrate of the aldehyde. ... 

Because of the electron-withdrawing sulfonic acid substituent, cleavage occurs under milder conditions than needed for the Fmoc group (0.1 N NH4OH 1% Na2C03, 45 min). ... 

In contrast to phosphorus esters, sulfur esters are usually cleaved at the carbon-oxygen bond with carbon-fluorine bond formation Cleavage of esteri nf methanesulfonic acid, p-toluenesidfonic acid, and especially trifluoromethane-sulfonic acid (tnflic acid) by fluoride ion is the most widely used method for the conversion of hydroxy compounds to fluoro derivatives Potassium fluoride, triethylamine trihydrofluoride, and tetrabutylammonium fluoride are common sources of the fluoride ion For the cleavage of a variety of alkyl mesylates and tosylates with potassium fluoride, polyethylene glycol 400 is a solvent of choice, the yields are limited by solvolysis of the leaving group by the solvent, but this phenomenon is controlled by bulky substituents, either in the sulfonic acid part or in the alcohol part of the ester [42] (equation 29)... 

An example of cleavage ol the sulfur-oxygen bond in trifluoromethane-sulfonic ester has been reported Tnfluororaethyl triflate reacts with neutral or anionic nucleophiles with elimination of carbonyl difluoride and formation of trifluoromethanesulfonyl fluoride [57] (equation 32) The mechanism of this reaction involves elimination of fluoride ion, which is a chain carrier in the substitution of fluorine for the trifluoromethoxy group... 

---