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Sulfur reagents in organic - Metzner P.

Metzner P., Thuiller A. Sulfur reagents in organic - Academic press, 1994. - 200 p.
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Oxidation of diphenyl disulfide with chloramine
Diphenyl disulfide (2.18g) and anhydrous chloramine T (4.56g) were stirred in dry acetone (50 ml) on ice for 3h. The solvent was removed under reduced pressure, and the residue taken up in dichloromethane (50 ml) and filtered through Celite. Ether (100 ml) was added and the solution
concentrated to give (1) as a pale-yellow crystalline product (5.01 g, 91%), m.p. 125-130C (decomposition).
From [215] with permission.
2- (Phenylthio )cyclooctanone
A stirred suspension of the adduct (1) (0.668 g, 1.2 mmol) in dichloromethane (10ml) was treated with l-(trimethylsilyloxy)cyclooctene (0.198g, l.Ommol). After completion of the reaction (20 min) the solution was concentrated in vacuo and the residue was partitioned between ether (50 ml) and water (15 ml). The organic phase was dried (MgS04) and concentrated in vacuo. The resulting solids were applied to a short column of silica gel (hexanes/ethyl acetate 7:3) to give 2-(phenylthio)cyclooctanone (0.20 g, 92%) as an oil.
From [214] with permission.
The oxidation step can be avoided if sulfinylation of the carbonyl compound can be conveniently realized. Methyl 2-pyridinesulfinate (2) has been prepared and used for sulfinylation-dehydrosulfinylation of ketones (Table 3.1) and esters [216].
Methyl 2-pyridinesulfinate
NBS (35.4g, 0.20 mol) was added in one portion to 2-mercaptopyridine (11.1 g, 0.10 mol) dissolved in 1:1 MeOH/CH2Cl2 (500 ml) at 0C. After
+ MeOH + 2 NBS---------

Dehydrogenation of ketones with methyl 2-pyridinesuIfinate
Yield (%)
* Yield after reacylation of a small amount of secondary alcohol with l-BuCOCl/Et,N.
being stirred for 15 min, the mixture was poured into saturated aqueous NaHCO, solution (300ml). The phases were separated and the aqueous layer was extracted with CH2C12 (6 X 200ml). The combined organic layers were washed with saturated aqueous NaCl, dried over MgS04, and
concentrated in vacuo to an orange oil. The oil was distilled through a 10 cm Vigreux column, b.p. 90-95C/0.06 torr, affording the sulfinate (2) (8.7 g, 55% ) as a clear oil.
From [216] with permission.
Sulfinylation of ketones and elimination
To a suspension of KH (3 eq, 35% dispersion in oil, washed with pentane under nitrogen) in THF at room temperature was added the ketone (1 eq) in sufficient THF to result in a 0.2 solution. Methyl 2-pyridinesulfinate (2) (1.1-1.5 eq) was introduced dropwise via a syringe, causing the solution to foam and turn red-orange. After a 1-5 min period, the reaction was poured into a sulfate buffer (pH 2). The aqueous phase was then adjusted to pH 6-7 with solid NaHC03 and extracted into ethyl acetate. The combined organic layers were washed with saturated aqueous NaCl solution, dried over MgS04, and concentrated in vacuo to a yellow oil which was thermolysed without further purification. A 0.1 solution of the 2-pyridylsulfinyl ketone and powdered cupric sulfate (2 eq) was heated to 110C for a period of 30 min to 2 h. The mixture was filtered, concentrated and submitted directly to chromatography on silica gel or distilled. Yields: 27-97%.
From [216] with permission.
A variety of sulfur reagents have been used for the dehydrohalogenation of vic-dihaloalkanes to alkenes. Aqueous sodium trithiocarbonate in the presence of a phase transfer catalyst was reported to give high yields under very mild conditions f217]. A radical mechanism involving a one-electron transfer was proposed as the first step in this reductive elimination.
Dehydrohalogenation ofmeso-l,2-dibromo-l,2-diphenylethane
To a solution of me.w-l,2-dibromo-l,2-diphenylethane (2mmol) in benzene (5 ml) was added a 30% aqueous Na2CSj solution (6mmol) and trioctylmethylammonium chloride (0.08 mmol). The mixture was stirred
3.1.2 Alkenes from 1,2-dihalo compounds
for lOmin at room temperature. After the completion of the reaction, the organic layer was washed with water and then dried over sodium sulfate. The residue obtained by evaporation of the solvent was passed through a short silica gel column, using dichloromethane as the eluent to give trans-stilbene (100% yield).
From [217] with permission.
The Corey-Winter olefin synthesis is based on the stereospecific loss of carbon dioxide or carbon disulfide from the carbenes formed by treatment with trivalent organophosphorus compounds of thionocarbonates or trithiocarbonates [218-220].
Vic-diols can thus be easily converted to alkenes through their reaction with N, N '-thiocarbonyldimidazule. The reported synthesis of trans-cyclooctene is illustrative of the method [219]. It should be noted that continuous elimination of rrans-cyclooctene by a stream of argon was necessary to avoid isomerization to the cis isomer. The conversion of cis-cyclooctene to frans-cyclooctene through a trithiocarbonate is described in the same paper.
3.1.3 Alkenes from 1,2-diols
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