Although a sulfur atom belongs to the same group 16 as an oxygen atom in the periodic table, it has specific properties which an oxygen atom does not. For example, the features of a sulfur atom include the following: the lone pair of a divalent sulfur atom has a soft and strong nucleophilicity but it has a weak affinity for hard acids such as a proton; the carbon-sulfur bond can be easily cleaved in various reactions; and it has a variety of atomic valences, etc. Organic sulfur compounds play important roles in organic synthetic chemistry because of the variety of their features. We introduce the following three examples of the role of sulfur compounds as reaction reagents in organic synthetic chemistry:
(1) Oxidizing agents
By the Swern oxidation and the Corey-Kim oxidization using DMSO, primary and secondary alcohols can be oxidized to aldehydes and ketones, respectively. In the Corey-Kim oxidation, dodecyl methyl sulfides (D3767) can be used to prevent the offensive odor of dimethyl sulfide.1)
(2) C-C bond formation in the alpha position
When 1,3-dithiane is treated with alkyllithium, an anion is generated in the C-2 position. The alkyl halide A reacts with this to give a monoalkylated 1,3-dithiane. Furthermore, by the same treatment, alkyl halide B reacts with this to give a dialkylated 1,3-dithiane. Therefore, two units, A and B, can be combined with a methylene unit.2) In addition, the dithioketal can be also obtained by protecting the ketone with 1,3-propanediol. It means that umpolung has occurred since the carbonyl carbon was originally positively-polarized.
(3) Leaving groups
Functional sulfur groups can be removed by treatment with reducing agents. Dithioketal shown in the examples above can be changed into methylene by reacting with hydrogen in the presence of the Raney-nickel catalyst. The modified Julia olefination is also known as the reductive elimination reaction of sulfones, and it is widely used for the total synthesis of natural products as a stereoselective olefin synthesis.3) E/Z selectivity varies with the type of aryl sulfone to be employed. Aryl sulfone is synthesized from the corresponding arylthiol. If ArSH is 2-mercaptobenzothiazole, the reaction is E-selective, but in the case of 2-mercaptopyridine, it becomes Z-selective.
In this section, we introduced the sulfur compounds used mainly in organic synthesis as reagents. We provide the building blocks, such as thiophenes and thiazoles, which can be found by a structure or keyword search on our website.
Disulfides
Sulfides
Thiols
Sulfenic Acid Derivatives
Thiocarbonyl Compounds
Sulfoxides
Sulfinic Acid Derivatives
Sulfones
Sulfonic Acids
Sulfonic Acid Derivatives
Others (Sulfur Compounds for Synthesis)
Disulfides
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| B3360 | Bis(2-methyl-3-furyl) Disulfide |
| D0538 | 2,2'-Dibenzothiazolyl Disulfide |
| D1114 | 2,2'-Dipyridyl Disulfide [for Peptide Synthesis] |
| D2477 | 4,4'-Dipyridyl Disulfide |
Sulfides
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Thiols
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Sulfenic Acid Derivatives
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| B2240 | N-tert-Butylbenzenesulfenamide |
| C1043 | Chlorocarbonylsulfenyl Chloride |
| M0979 | Methoxycarbonylsulfenyl Chloride |
| T1237 | Triphenylmethanesulfenyl Chloride |
Thiocarbonyl Compounds
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Sulfoxides
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Sulfinic Acid Derivatives
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Sulfones
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Sulfonic Acids
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| B0030 | Benzenesulfonic Acid Monohydrate |
| I0758 | 2-Iodobenzenesulfonic Acid Dihydrate |
| T0267 | p-Toluenesulfonic Acid Monohydrate |
Sulfonic Acid Derivatives
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Others (Sulfur Compounds for Synthesis)
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Literature
2) D. Enders, T. Schuseler, Tetrahedron Letters, 2002, 43, 3467 [DOI].
3) D. A. Alonso, C. Najera, M. Varea, Tetrahedron Lett., 2004, 45, 573 [DOI]; Review: P. R. Blakemore, J. Chem. Perkin Trans. 1, 2002, 2563 [DOI].
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