“…Several 3-phenyl-4-arylthiophenes 24 were prepared by the Suzuki cross-coupling reaction 39 of 3-iodo-4phenylthiophene (21) with areneboronic acids in good yields. As such, this procedure provides a general route to unsymmetrical 3,4-diarylthiophenes.…”
Section: Resultsmentioning
confidence: 99%
“…Thiocarbonyl ylides are useful reactive intermediates for the synthesis of heterocycles containing a sulfur atom. The parent thiocarbonyl ylide, namely thioformaldehyde S -methylide ( 3 ), can be generated by two methods: , one involved the release of disiloxane from bis(trimethylsilylmethyl) sulfoxide ( 4 ) through a pathway related to the sila-Pummerer rearrangement, the other involved the 1,3-elimination of chloromethyl (trimethylsilyl)methyl sulfide ( 5 ) catalyzed by cesium fluoride in acetonitrile at room temperature (Scheme ). 2 …”
Section: Resultsmentioning
confidence: 99%
“…(a) Bis(trimethylsilylmethyl)sulfoxide (4). To a solution of acetonitrile (3 mL) containing bis[(trimethylsilyl)methyl] sulfide ( 8 ) 24a (206 mg, 1 mmol) in a 50-mL round-bottomed flask was added an aqueous solution of sodium metaperiodate (257 mg, 1.2 mmol) in water (3 mL) at −10 °C by ice−salt bath cooling. The solution was stirred at −10 to 0 °C for 12 h, and then the cold solution was filtered and extracted with cold dichloromethane (3 × 5 mL).…”
Section: Methodsmentioning
confidence: 99%
“…The spectroscopic data coincide with the previous report. 21 (b) 3,4-Bis(trimethylsilyl)-2,5-dihydrothiophene (9). In a flame dried 100-mL three-necked round-bottomed flask equipped with a water condenser and a dropping funnel was added a solution of 4 (666 mg, 3 mmol) and bis(trimethylsilyl)acetylene (13a) (340 mg, 2 mmol) in dry HMPA (2 mL) (distilled from CaH2) rapidly from a dropping funnel to dry HMPA (2 mL), and the resulting solution was warmed at 100 °C and stirred at this temperature for half an hour under nitrogen atmosphere.…”
3,4-Bis(trimethylsilyl)thiophene (1a) was synthesized by three routes: (a) 1,3-dipolar cycloaddition; (b) modification of 3,4-dibromothiophene; and (c) intermolecular thiazole-alkyne Diels-Alder reaction. 3,4-Bis(trimethylsilyl)thiophene (1a) can function as a versatile building block for the construction of unsymmetrically 3,4-disubstituted thiophenes utilizing its stepwise regiospecific mono-ipso-substitution followed by palladium-catalyzed cross-coupling reactions. In this manner, thiophenes 15, 16, 17a-j, 19a,b, 20, 22a-c, 23a,b, 24a-d, 25a-c, and 27a-j were prepared. The thiophene-3,4-diyl dimer 28 and thiophene-3,4-diyl tetramer 29 were also realized by palladium-catalyzed self-coupling reaction of organoboroxines. The stannylthiophene 31, formed by conversion of the C-Si bond to a C-Sn bond via boroxine 26c underwent both carbonylative coupling and lithiation followed by quenching with electrophiles to afford unsymmetrically 3,4-disubstituted thiophenes 33 and 36a-c as well. Moreover, 3,4-bis(trimethylsilyl)thiophene (1a) can be used as the starting material for the generation of the highly strained cyclic cumulene 3,4-didehydrothiophene (2), whose existence was substantiated by its trapping reaction with several alkenes.
“…Several 3-phenyl-4-arylthiophenes 24 were prepared by the Suzuki cross-coupling reaction 39 of 3-iodo-4phenylthiophene (21) with areneboronic acids in good yields. As such, this procedure provides a general route to unsymmetrical 3,4-diarylthiophenes.…”
Section: Resultsmentioning
confidence: 99%
“…Thiocarbonyl ylides are useful reactive intermediates for the synthesis of heterocycles containing a sulfur atom. The parent thiocarbonyl ylide, namely thioformaldehyde S -methylide ( 3 ), can be generated by two methods: , one involved the release of disiloxane from bis(trimethylsilylmethyl) sulfoxide ( 4 ) through a pathway related to the sila-Pummerer rearrangement, the other involved the 1,3-elimination of chloromethyl (trimethylsilyl)methyl sulfide ( 5 ) catalyzed by cesium fluoride in acetonitrile at room temperature (Scheme ). 2 …”
Section: Resultsmentioning
confidence: 99%
“…(a) Bis(trimethylsilylmethyl)sulfoxide (4). To a solution of acetonitrile (3 mL) containing bis[(trimethylsilyl)methyl] sulfide ( 8 ) 24a (206 mg, 1 mmol) in a 50-mL round-bottomed flask was added an aqueous solution of sodium metaperiodate (257 mg, 1.2 mmol) in water (3 mL) at −10 °C by ice−salt bath cooling. The solution was stirred at −10 to 0 °C for 12 h, and then the cold solution was filtered and extracted with cold dichloromethane (3 × 5 mL).…”
Section: Methodsmentioning
confidence: 99%
“…The spectroscopic data coincide with the previous report. 21 (b) 3,4-Bis(trimethylsilyl)-2,5-dihydrothiophene (9). In a flame dried 100-mL three-necked round-bottomed flask equipped with a water condenser and a dropping funnel was added a solution of 4 (666 mg, 3 mmol) and bis(trimethylsilyl)acetylene (13a) (340 mg, 2 mmol) in dry HMPA (2 mL) (distilled from CaH2) rapidly from a dropping funnel to dry HMPA (2 mL), and the resulting solution was warmed at 100 °C and stirred at this temperature for half an hour under nitrogen atmosphere.…”
3,4-Bis(trimethylsilyl)thiophene (1a) was synthesized by three routes: (a) 1,3-dipolar cycloaddition; (b) modification of 3,4-dibromothiophene; and (c) intermolecular thiazole-alkyne Diels-Alder reaction. 3,4-Bis(trimethylsilyl)thiophene (1a) can function as a versatile building block for the construction of unsymmetrically 3,4-disubstituted thiophenes utilizing its stepwise regiospecific mono-ipso-substitution followed by palladium-catalyzed cross-coupling reactions. In this manner, thiophenes 15, 16, 17a-j, 19a,b, 20, 22a-c, 23a,b, 24a-d, 25a-c, and 27a-j were prepared. The thiophene-3,4-diyl dimer 28 and thiophene-3,4-diyl tetramer 29 were also realized by palladium-catalyzed self-coupling reaction of organoboroxines. The stannylthiophene 31, formed by conversion of the C-Si bond to a C-Sn bond via boroxine 26c underwent both carbonylative coupling and lithiation followed by quenching with electrophiles to afford unsymmetrically 3,4-disubstituted thiophenes 33 and 36a-c as well. Moreover, 3,4-bis(trimethylsilyl)thiophene (1a) can be used as the starting material for the generation of the highly strained cyclic cumulene 3,4-didehydrothiophene (2), whose existence was substantiated by its trapping reaction with several alkenes.
“…5a,39 The thiocarbonyl ylide was readily generated in situ through a sila-Pummerer rearrangement upon heating of bis(trimethylsilylmethyl) sulfoxide. 39 Ohno, Itoh and coworkers treated a number of these thiolene derivatives with Oxone, providing the 3-sulfolenes 67. 5a The furnished 3sulfolenes were heated with fullerene (C 60 ) in refluxing 1,2dichlorobenzene to afford several substituted fullerenes 69 (Scheme 16).…”
Section: Scheme 15 Access To 2-sulfolenes Using 14-ketoxanthatesmentioning
The diverse substitution patterns available to 3-sulfolenes have long made them useful for the preparation of multi-substituted 1,3-diene equivalents. More recently, the 3-sulfolene motif itself (or its reduced sulfolane congener) is finding increasing application as a structural element in the creation of molecules for biological applications. This review describes various methods to afford 3-sulfolene building blocks and their derivatives. Selected applications in synthetic and medicinal chemistry are also discussed. 1 Introduction 2 The Preparation of Monocyclic Sulfolene Building Blocks 2.1 Sulfolenes through Electrophilic Addition 2.1.1 Sulfolenes through Nucleophilic Addition to 4-Bromo-2-sulfolene 2.2 Sulfolenes through Oxidation of a Thiol Precursor 2.3 Sulfolenes through Noble Metal Catalysis 2.4 Sulfolenes through Deprotonation Followed by Alkylation 3 Synthesis of Bicyclic Sulfolenes and Their Derivatives 3.
The Pummerer reaction involves the formation of an α‐functionalized sulfide from a sulfoxide bearing at least one α‐hydrogen atom. The reaction can also be described as an internal redox process where the SX group is reduced and the α carbon is oxidized.
The first report by Pummerer on the reaction which now bears his name appeared in 1909 and described the formation of thiophenol and glyoxylic acid on heating phenylsulfinylacetic acid with mineral acids. The products Pummerer observed resulted from hydrolysis of the initially formed α‐substituted sulfides, which are the typical products of the reaction. The term “Pummerer reaction” was later extended to the reaction of sulfoxides with acid anhydrides.
Selenium and nitrogen analogs undergo similar reactions. The former is known as the seleno–Pummerer reaction, and the latter is usually referred to as the Polonovski reaction. The sila–Pummerer reaction, which is also discussed in this chapter, is the rearrangement of sulfoxides bearing a silyl group on the α carbon.
From a mechanistic point of view there are many other reactions, sometimes given specific names, such as the Sommelet–Hauser, Stevens, and Vilsmeier rearrangements, that appear to resemble the Pummerer reaction. Reactions in which the sulfoxide group acts as an oxidant in an intermolecular redox process have characteristics similar to the typical Pummerer reaction. The α‐halogenation of sulfides, in which the sulfide sulfur may first be oxidized to a halosulfonium salt that rearranges to the final product, is formally similar to the Pummerer reaction.
For the sake of clarity and to be as exhaustive as possible, we have limited the scope of this chapter to the restrictive definition.
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