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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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Benzaldehyde 55
Benzophenone 78
4-Phenylbutan-2-one 72
3-Mcthylbutan-2-one 47
Cyclohexanone 55
t-Butylcyclohexanone 71
1 -(2,4-Dichlorophenyl)pentan-l-one 86
aThe product consisted of an 1:1 mixture of diastereoisomers.
a-thiomethylcne ketones [452] in a pivotal step towards the synthesis of
3,4-substituted furans [453].
i) dimethylsulfonium methylide: from trimethylsulfonium methylsulfate [452] or from fluoborate [453]. il) rt, 24 h. ) HgS04, El^O 1453] or 2 N aq. HC1 [452].
The reaction of a-oxoketene dithioacetals with dimethylsulfonium methylide led to another general route to furans and butenolides [454]. according to the accompanying scheme.
The methylthio group in (4) can be substituted by Grignard reagents, removed by Raney nickel, or hydrolysed into a carbonyl group to yield a variety of furans and butenolides in fair to good yields.
The methodology was applied to the syntheses of perillene and rose furan, and as an example the synthesis of 3-phenylfuran (R1 = Ph, R2 = H) is given.
Synthesis of bis(methylthio)dihydrofurans
To trimethylsulfonium tetrafluoborate (2.4mmol, 400mg) in THF (13 ml) was added n-butyllithium in hexane (2.4 mmol) at -10C under an argon atmosphere, and the mixture was stirred for 15 min at this temperature to produce the ylide. To the solution cooled to -70C was added a THF solution (7 ml) of (1) (2.0mmol), which was stirred for 10 min at this temperature and then for lh at room temperature. The reaction was quenched with water (0.5 ml) and the THF was evaporated below 30C. After addition of brine (40 ml) and extraction with ether or dichloromethane, the organic layer was dried (MgS04) and concentrated. The dihydrofurans thus obtained were stored in a refrigerator below -10C. (3) (R1 = Ph, R2 = H) was isolated in a 92% yield.
From [454] with permission.
Conversion of bis(methylthio)dihydrofurans to (methylthio)furans
To a methanol solution (5 ml) of (3) (1 mmol) was added 2 hydrochloric acid (0.2 ml) and the solution was stirred for 1 h at room temperature. The
solution was neutralized with aqueous sodium carbonate and extracted with ether. The combined ethereal solution was washed with brine, dried (MgS04) and concentrated. (4) (R1 = Ph, R2 = H) was purified by Florisil chromatography, colourless crystals (91%), m.p. 32-34C, b.p. 60C/0.02 torr.
From [454] with permission.
To an acetone solution (6 ml) of the preceding (methylthio)furan (190 mg,
1 mmol) was added Raney nickel W-7 (prepared from 1 g of Raney Ni alloy) in ethanol (12 ml) and the solution was stirred for 30 min at room temperature. After filtration and washing (ethanol) of the Raney Ni, the filtrate was concentrated in vacuo. To the residue was added brine (20 ml) and the solution was extracted with ether. The combined ethereal solution was dried (MgS04), concentrated, and subjected to chromatography on Florisil (elution with pentane) to give 3-phenylfuran (42%), colourless crystals, m.p. 51-57C.
From [454] with permission.
Dimethylsulfoxonium methylide (DMSY, also referred to as Coreys reagent) is a convenient methylene transfer reagent. It appears to be the most used sulfur ylide and a Tetrahedron Report [455] covers most of its chemistry (345 references). In contrast to dimethylsulfonium methylide, which must be used as soon as it is formed, DMSY is much more stable and can be stored for several days at room temperature. It is the reagent of choice in many instances. However, with a,P-unsaturated ketones the two reagents react in different ways, as shown for cyclohexenone.
Kinetic control and thermodynamic control account, respectively, for epoxide formation and cyclopropanation [204]. Various Michael acceptors have been converted to cyclopropane derivatives with sulfur ylides. Some of the reagents used to transfer CHCOR [456], CHCOOR [457], CHMe
[458], CMe2 [458, 459] and cyclopropylidcne [458, 460-463] groups are listed below:
Me Me
iSI&h phl^
Particularly interesting applications of isopropylidenediphenylsulfuran [459, 464] have been reported. Improvements in its preparation and use led [465] to a claimed industrially viable stereoselective synthesis of Deltamethrin, the most potent commercially available insecticide, as well as to other stereoselective syntheses of cyclopropane derivatives [466].
N-(p-Tolyl sulfonyl)sulfonimidoyl-stabilized carbanions act in a similar way to nucleophilic alkylidene transfer reagents with electrophilic double bonds (C=0, C=N activated C=C) [467]. The example given here is illustrative.
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