Dimsyl sodium

The formation of the above anions ("enolate type) depend on equilibria between the carbon compounds, the base, and the solvent. To ensure a substantial concentration of the anionic synthons in solution the pA" of both the conjugated acid of the base and of the solvent must be higher than the pAT -value of the carbon compound. Alkali hydroxides in water (p/T, 16), alkoxides in the corresponding alcohols (pAT, 20), sodium amide in liquid ammonia (pATj 35), dimsyl sodium in dimethyl sulfoxide (pAT, = 35), sodium hydride, lithium amides, or lithium alkyls in ether or hydrocarbon solvents (pAT, > 40) are common combinations used in synthesis. Sometimes the bases (e.g. methoxides, amides, lithium alkyls) react as nucleophiles, in other words they do not abstract a proton, but their anion undergoes addition and substitution reactions with the carbon compound. If such is the case, sterically hindered bases are employed. A few examples are given below (H.O. House, 1972 I. Kuwajima, 1976). 

Care is required ia miming these reactions because the decomposition of the intermediate sulfoxide and of dimsyl sodium during the heating in the strongly alkaline system is exothermic and also produces a precipitate which can interfere with heat removal. Explosions have occurred (51). 

Trimethylsulfoxonium iodide (11) is of interest because treatment with sodium hydride or dimsyl sodium produces dimethyl sulfoxonium methylide [5367-24-8] (12) (eq. 22), which is an excellent reagent for introducing a methylene group into a variety of stmctures (53) ... 

Reaction of ethyl picolinate (12) with dimsyl sodium (from dimethylsulfoxide and sodium hydride)... 

A preparation of dimsyl sodium from sodium and DMSO, on 14 litre scale, overheated, then exploded causing two fatalities. It has not proved possible to duplicate the runaway. 

A solution of NaGaCH in DMSO may be prepared by reacting acetylene with dimsyl sodium (prepared from NaH and DMSO) in DMSO [39], other acetylenes can in principle be metallated in a similar way. The kinetic stability of NaC CCHjR in DMSO is limited, however. At somewhat elevated temperatures a slow isomerization to CHjCsCR occurs, whereby DMSO acts as the proton source [37]. 

Ring cleavage of a-alkenoyl cyclic ketene dithioacetals by dimsyl sodium generates a thiolate anion and induces an intramolecular Michael cyclization which produces 2,3-dihydrothiopyran-4-ones n good yields (Scheme 218) <2000SL1804, 2007S2115>. 

In the reaction of the benzylisoquinoline 72 with dimsyl sodium, it has been suggested that a proerythrinadienone intermediate results from nucleophilic attack on a benzyne formed in the lower ring. This postulated intermediate was thought then to rearrange to an iminium salt which is trapped by the dimsyl sodium to give 73a, which on reduction and desulfuration would finally lead to dibenzazonine 74 (60) (Scheme 19). Later work, however, proved that the product of the dimsyl sodium treatment is instead the dibenz[6,/]azonine (73b), which is formed by N-attack on the intermediate benzyne followed by cleavage of the C-N+ bond (67). 

To our knowledge, no isomerizations of 3-piperideines (111) to the enamines (112) have been observed in alkaline media,98,111 except for a preliminary communication on the so-called deconjugation of l-methyl-4-(2-indolylcarbonyl)-3-piperideine (114) to the enamine (115) by the action of dimsyl sodium. 112... 

Alkyl thiol anions displace halogens from halocodides to give corresponding alkylthiocodides. 192 Dihydrocodeinone (78) has been reported 200 to react with sodium dimethyloxosulfonium methylide (dimsyl sodium), giving the 6-oxirane (91), which opened under reducing conditions to the methyl carbinol, 92, an analgesic similar in potency to codeine. 

It has been reported [23] that the anion generated from 2-(N-alkylamino)-ethanol with dimsyl sodium in DMSO reacted with 4-chloronitrobenzene to afford ether 32. Rearrangement of 32 into 33 took place after water was added. Accordingly, 32 rearranged in high yield when NaOH in aq. DMSO at 60 °C was used (Scheme 13). 

In strong bases such as the one provided by sodium hydride and dimethyl sulfoxide (DMSO)—namely, dimsyl sodium—one should expect the formation of carbanions at sites of acidic protons. Ketones are attractive as potential sources of carbanions. However, ketone I features two blocked a carbons, without protons. Conversely, the tosyl group is ill suited for carbanion stabilization. The last functionality one may appeal to is the phenyl sulfone substituent at the end of the jec-pentyl chain. Recent investigations have revealed their potential as carbanion precursors, adding an important feature to their considerable usefulness in organic synthesis That is, sulfones can be removed under such mild conditions that carbonyl groups are not affected, and unconstrained a-sulfonyl carbanions have the unusual quality of retaining the asymmetry of their precursors in a wide variety of experimental conditions. ... 

Ishwarane (371) has been isolated from the petals of Cymbopetalum penduli-forum (Dunal) Baill. Last year, Kelly et al. reported the synthesis of isoish-warane (372) which they have now extendedto the synthesis of ishwarane itself. The enone (373) was converted in five steps into the ketol (374). Treatment of the tosylate of (374) with dimsyl sodium afforded the cyclized ketone (375) which gave ishwarane on Wolff-Kishner reduction. The complete details of the elegant synthesis of hinesol (376) by Marshall and Bradyhave now been published. 

A lot of progress in this area is due to the work of Trost, who introduced diphenylsulphonium cyclopropylide and phenylthiocyclopropyl lithium as extremely versatile C3-building blocks. The first reagent is easily available from the corresponding sulphonium salt by deprotonation with suitable bases (either under irreversible conditions with dimsyl sodium, or, preferably, in a reversible manner by employing potassium hydroxide in DMSO). The ylide adds to a,) -unsaturated carbonyl compounds forming... 

More investigations have been performed with cyclopropyl ketones. The isomerization of the cis-cyclopropyl ketone 209 to its trans isomer 210 was only achieved by means of the rather basic dimsyl sodium in dimethyl sulfoxide at 60°C . Similarly, esters of cyclopropane carboxylic acids have been isomerized ... 

An elegant route to 11-deoxyprostaglandins uses a 1,5 attack of an enolate on such an activated cyclopropane. The ring-opening of activated cyclopropanes by intramolecul-arly situated nucleophiles has also been achieved An interesting case of intramolecular 1,7 attack on an activated vinylcyclopropane was observed upon treatment with dimsyl sodium-Me2SO at 90°C (equation 18) . 

Immonium salts can also be used in the benzyne reaction. Treatment of salt (32) with dimsyl sodium in DMSO gave a 25% yield of dehydrodomesticine which was reduced to domesticine. Similarly, salt (33) furnished 1-hydroxy-2,10-dimethoxydehydroaporphine which was readily reduced to the corresponding aporphine. ... 

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