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Sulfur reagents in organic - Metzner P.

Metzner P., Thuiller A. Sulfur reagents in organic - Academic press, 1994. - 200 p.
Download (direct link): sulfarreagents1994.djvu
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From [390] with permission.
This synthesis involves three different steps without isolating the intermediate products.
(1) To a solution of p-hydroxysulfone (4) (lmmol) in THF (10 ml) at -78C was added dropwise n-BuLi (2.2 eq) in hexane. After 2h at -10C the yellow solution was cooled at 78C and sodium iodoacetate (1.2 eq) was added. After 1 h at -10C the reaction mixture was allowed to react at
room temperature for 15h. After quenching with saturated ammonium chloride (2 ml), extraction and separation of the organic layer, the aqueous phase was acidified by 10% HC1 and extracted with ether (3 X 5 ml). The organic layers were dried and evaporated, giving a crude p-sulfonyl-8-hydroxyacid, which was used in the next step without further purification.
(2) This crude product was dissolved in benzene (50 ml) and a catalytic amount of p-toluenesulfonic acid was added. After refluxing for 3h in a Soxhlet filled with molecular sieves, the mixture was treated with a 5% aqueous solution of NaHCO- (10 ml). After extraction with benzene, the organic layers were dried over sodium sulfate and concentrated to 50 ml.
(3) Triethylamine (4 eq) was added to the solution, which was stirred at room temperature for 15 h. The mixture was washed with 10% HC1 (10ml), dried and evaporated. The overall yield of (la) for the three steps after purification by chromatography (eluent: ether/cyclohexane 50:50) was around 50%, m.p. 59-61C. Isomer (S)-(la) [a]D = +90 (c 2 in dioxane). Isomer (.R)-(la) [a]D = -92 (c 2 in dioxane).
From [390] with permission.
A remarkably high diastereoselective excess was obtained in the addition of the anion of (5)-()-methyl 1-naphthyl sulfoxide to n-alkyl phenyl ketones. The sulfoxide was prepared in optically pure form by oxidation of the complex of methyl 1-naphthyl sulfide and (i-cyclodextrin with peracetic acid followed by crystallization. Desulfurization of the adducts provided enantiomerically pure tertiary alcohols [393].
enantiopure (S)-alcohol R n-alkyl
Analogously, (/?)-(-)-chloromethyl p-tolyl sulfoxide has been prepared with 97% e.e. and used for the enantioselective synthesis of epoxides
A recoverable cyclic sulfinamide has been proposed as a source of chiral sulfoxides for asymmetric synthesis [395].
The stabilized carbanion a to a sulfonyl group has been used mainly for carbon-carbon bond-forming purposes by reactions with electrophiles [109, 110, 386]. Their importance is based on the efficiency of their preparation, of their use particularly for alkylation procedures and on the elaboration of reliable methods for sulfonyl group elimination. One example is shown here, with a synthesis of a//-mms-squalene [396] close to the Biellman synthesis (see Section
H Me

4.2.9 Use of sulfones
i) n-Buti
li) Li/EtNH2
For the reductive desulfonylation step, necessary when the formation of a single bond is wanted, a number of electron transfer agents are available [397]. A mild and convenient method makes use of magnesium in ethanol
in the presence of a catalytic amount of mercuric chloride; alkyl and vinyl phenyl sulfones yield the corresponding alkanes and alkenes [398].
3 eq Mg, cat HgCl2
R-SO,Ph --------------------------
EtOH, rt, 2 b
R = alkyl, vinyl
Desulfonylation of alkyl or vinyl phenyl sulfones
A mixture of the substrate (2.0 mmol), Mg (146 mg, 6.0 mmol, powder 50 mesh) and a few crystals of HgCl2 in dry EtOH (10ml) was stirred for 2h at room temperature. The reaction mixture was poured into cold 0.5 N HC1 and extracted with pentane or ether. The organic layer was washed with saturated aqueous NaHCOj solution, dried (MgS04), filtered and concentrated in vacuo to give a crude product, which was purified by flash column chromatography (Si02).
From [398] with permission.
In some instances the relatively easy homolytic cleavage of the C-S02 bond could be used for an efficient synthesis of polycyclic hydrocarbons, particularly cydophanes and benzocyclobutene via pyrolysis of sulfones at temperatures of 300-900C (see [203] for references on these reactions). An example [399] is:
The usefulness of this pyrolytic method is emphasized by the synthesis of w-[3410][7]metacyclophane [400].
Other synthetic approaches via sulfones make use of the Michael addition and cycloaddition to vinyl sulfones (see [401] and [402] for reviews on vinyl sulfones as dienophiles and Michael acceptors). The
following example is detailed in Organic Syntheses [403]:

i) xylene 125C
' SOaPh
The preparations of the starting sulfones are also given [404]. See [405] for the synthesis of 2-(phenyIsulfonyl)-l,3-cyclohexadiene and related dienes.
A remarkable stereospecific dehydrative alkylation of p-disulfones was reported by Falck et al. [406] under Mitsunobu conditions (triethyl phosphine, diethyl azodicarboxylate). The synthesis of a pheromone component of the lesser tea tortrix emphasizes some of the possibilities offered by coupling this reaction with further uses of the sulfone functionality. In the present case, monodesulfonylation with lithium naphthalenide (-78C, 5 min), in situ alkylation (-78 to 23C, 1 h), and Li-naphthalene cleavage of the second sulfonyl group (-78C, 5 min) yielded in a one-pot procedure a THP ether which was converted into the sought after pheromone through direct acetylation.
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