Alkenes sulfonation with

Desulfonylation of equally substituted allylic sulfones with NaBH4 and LiBHEt3 usually yields a mixture of regioisomeric alkenes[406,407]. However, the regioselective attack of the less substituted side of the unsymme-trically substituted allylic system with LiEtjBH has been utilized for the removal of the allylic sulfone group in synthesis of the polyprenoid 658[408],... 

A.lpha-Olefm Sulfonates. Sulfonation of alpha-olefins yields a mixture of alkene sulfonates, hydroxyalkane sulfonates, and some amount of various disulfonates. These detergents are excellent foamers with good detergency properties. They are unaffected ia hard water and thek effects are considered superior to the alkyl ether sulfates (9). 

Sulfur trioxide reactivity can also be moderated through the use of SO adducts. The reactivity of such complexes is inversely proportional to their stabihty, and consequentiy they can be selected for a wide variety of conditions. Whereas moderating SO reactivity by adducting agents is generally beneficial, the agents add cost and may contribute to odor and possible toxicity problems in derived products. CeUulosic material has been sulfated with SO.—trimethyl amine adduct in aqueous media at 0 to 5°C (16). Sulfur trioxide—triethyl phosphate has been used to sulfonate alkenes to the corresponding alkene sulfonate (17). Sulfur trioxide—pyridine adduct sulfates oleyl alcohol with no attack of the double bond (18). 

Allylic sulfones and a, /5-unsaturated sulfones are known to be in equilibrium314-319. Allylic sulfones, such as 242, isomerize to a, /5-unsaturated sulfones 243 upon treatment with a catalytic amount of potassium t-butoxide in dry THF. The a, /5-unsaturated sulfones can be converted to the corresponding olefins upon desulfonation with sodium amalgam320 or aluminium amalgam294,321. Since treatment of allylic sulfones with potassium-graphite gives 2-alkenes, alkylation of allylic sulfones and subsequent desulfonation is a useful process for the synthesis of olefins, as shown in Scheme 6. 

The ene reaction130 of ethynyl p-tolyl sulfone with alkenes has been investigated by Snider and coworkers131 using EtAlCl2 as a Lewis acid catalyst (equation 136). The reaction is very sluggish requiring 4 to 18 days at room temperature to obtain a reasonable... 

The reaction of an a-halo sulfone with a base to give an alkene is called the Ramberg-Bdcklund reaction. The reaction is quite general for a-halo sulfones with an (x hydrogen, despite the unreactive nature of a-halo sulfones in normal 8 2 reactions (p. 437). Halogen reactivity is in the order I>Br>Cl. Phase-transfer catalysis has been used. In general, mixtures of cis and trans isomers are obtained, but usually the less stable cis isomer predominates. The mechanism involves formation of an episulfone, and then elimination of SO9. There is much evidence for... 

Wilkinson s catalyst has also been utilized for the hydroboration of other alkenes. Sulfone derivatives of allyl alcohol can be hydroborated with HBcat and subsequently oxidized to give the secondary rather than primary alcohol. This reactivity proves to be independent of substituents on the sulfur atom.36 Similarly, thioalkenes undergo anti-Markovnikoff addition to afford a-thioboronate esters.37 The benefits of metal-catalyzed reactions come to the fore in the hydroboration of bromoalkenes (higher yields, shorter reaction times), although the benefits were less clear for the corresponding chloroalkenes (Table 3).38,39 Dienes can be hydroborated using both rhodium and palladium catalysts [Pd(PPh3)4] reacts readily with 1,3-dienes, but cyclic dienes are more active towards [Rh4(CO)i2].40... 

The application of collision-induced dissociation (CID(—)) to re-alkane- or linear (primary) alkyl sulfonates (PASs CraH2n+1-S03) or their isomers, the SASs with the modified formula CH3—(CH2)n— CIKSO3)—(CH2)X—CH3, and alkene sulfonates using FIA—MS—MS(—) conditions leads to only one, not quite specific, fragment ion at m/z 80,... 

The addition reactions which were discussed in Sections 4.1 and 4.2 are initiated by interaction of a proton with the alkene, which causes nucleophilic attack on the double bond. The role of the initial electrophile can be played by metal cations as well. Mercuric ion is the reactive electrophile in several synthetically valuable procedures.12 13 The most commonly used reagent is mercuric acetate, but the trifluoroacetate, trifluoromethane-sulfonate, or nitrate salts are preferable in some applications. A general mechanism depicts a mercurinium ion as an intermediate.14 Such species can be detected by physical measurements when alkenes react with mercuric ions in nonnucleophilic solvents.15 Depending on the structure of the particular alkene, the mercurinium ion may be predominantly bridged or open. The addition is completed by attack of a nucleophile at the more substituted carbon ... 

An enantioselective synthesis of (+)-estradiol has been accomplished from 1,3-dihy-drobenzo[c]thiophene 2,2-dioxide (306) by successive thermal S02-extrusion and cycloaddition (80HCA1703). Treatment of the optically active iodide (307) with two mole equivalents of the masked quinodimethane (306) in the presence of two mole equivalents of sodium hydride gave (308) as a 1 1 mixture of diastereoisomers. Thermolysis of this alkenic sulfone in 1,2,4-trichlorobenzene furnished the trans-anti-trans steroid (309) in 80% yield. Treatment of (309) with methyllithium gave the methyl ketone, which was subjected to a Baeyer-Villiger oxidation and then silyl ether-acetate cleavage to afford (-l-)-estradiol (310 Scheme 66). 

Cyclopropanation of 1 -alkenes.1 /-Butylsulfonylmethyllithium, generated in situ from this sulfone with methyllithium, serves as a methylene transfer reagent under catalysis with Ni(acac)2. Terminal alkenes and cyclic 1,2-disubstituted alkenes are cyclopropanated in 70-95% yield, but open-chain 1,2-disubstituted alkenes do not react with this reagent. Other alkyl methyl sulfones are much less effective for this purpose. 

Alkene synthesis.9 The key step in the Julia synthesis of alkenes (11, 473-475) involves reductive elimination of a P-hydroxy sulfone with sodium amalgam. A recent modification involves elimination of a p-hydroxy imidazolyl sulfone with Sml2 (equation I).1 Both syntheses are particularly useful for preparation of disubstituted alkenes and conjugated dienes and trienes. Both methods of elimination favor formation of (E)-alkenes. In a direct comparison, a higher yield was obtained with Sml2 than with Na(Hg). 

The treatment of /3-sultones with hydrochloric acid results in ring-opening products and is initiated by protonation of the ring oxygen atom. For example, Scheme 12 highlights the conversion of the /3-sultones 53 into the corresponding 2-chlorosulfonic acids 54 and the (E)- and (Z)-alkene-sulfonic acids 55 when exposed to HC1 <1999EJ091>. 

Treatment of arenesulfinate salts with Cu2+, Mn3+, or Ce4+ generates arenesulfonyl radicals, via single electron oxidation. Thus, reaction of alkene (50) with p-TsNa in the presence of Cu(OAc)2 in AcOH gives p-tolyl allyl sulfone (51) through the addition of a toluenesulfonyl radical onto alkene, oxidation of the formed carbon-centered radical with Cu2+, and then deprotonation (eq. 4.20a). This reaction requires acidic conditions for effective oxidation with Cu2+ or Mn3+ [53-58]. Eq. 4.20b is the same addition... 

Reaction with concentrated sulfuric acid. Alkenes react with cold concentrated sulfuric acid by addition. Alkyl sulfonic acids form as products and are soluble in H2S04. 

The reduction of sulfones with Sml2 can result in deoxygenation, to give the parent sulfide,59 or carbon-sulfur bond cleavage, depending on the substrate and the reaction conditions employed.60 For example, alkyl and alkenyl phenyl sulfones are reductively cleaved by Sml2 in the presence of HMPA. In the reduction of alkenyl sulfones, competing reduction of the electron-deficient alkene is not observed (Scheme 4.50).60... 

Alkyl radicals generated from the reduction of halides or sulfones with Sml2 have been successfully exploited in intramolecular additions to alkenes that result in the generation of a variety of functionalised small carbocyclic and heterocyclic ring systems. Substrates containing an oxygen atom within the... 

Olefin synthesis. Condensation of aldehyde tosylhydrazones with stabilized carbanions affords alkenes by an addition-fragmentation process. The overall sequence is formulated in equation (I). Functional groups such as sulfides, sulfones, thioacetals, hemithioacetals, and nitriles can serve as Y, the anion stabilizing group in 2 and the leaving group in 3. When Y = SO2R, the anions 1 and 2 are conveniently prepared by treatment of a mixture of the tosylhydrazone and sulfone with LDA in... 

Desulfonylation. Allylic sulfones with a terminal double bond (1) react with tri-n-butyltin hydride (azobisisobutyronitrile initiation or irradiation) to form allyl-tin derivatives (2), which on protonolysis give terminal alkenes (3). The reaction can be conducted without isolation of 2 in 80-87% overall yield. 

Sulfonic acids add to alkenes and alkynes. The reaction of an alkyne with ara-toluenesulfonic acid and treatment with silica gives the vinyl sulfonate (C=C—OS02To1) Cyclic sulfonates can be generated by the reaction of an allylic sulfonate salt (C=C—C—OSOs ) with silver nitrate in acetonitrile containing an excess of bromine and a catalytic amount of water. Sultones are formed when alkenes react with PhlO and two equivalents of Me2SiS03Cl. ... 

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