Syntheses of Thiophenes with Group I Substituents

Gronowitz, Salo; Hörnfeldt, Anna‐Britta

doi:10.1016/b978-012303953-8/50001-1

Cited by 6 publications

(6 citation statements)

References 782 publications

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“…30 2-Bromo-5-(chloromethyl)thiophene (used in the synthesis of diethyl {(2bromo-5-thienyl)methyl}phosphonate) 28 has previously been prepared by chloromethylation of 2-bromothiophene, 31 but in the present work was synthesized by reaction of thionyl chloride with 2-bromo-5-(hydroxymethyl)thiophene. 32 2,5-Dibromoselenophene was obtained as the major product from the direct bromination of selenophene with bromine, 33 but it could not be chromatographically separated from the 2,4-dibromoselenophene and 2,3,4,5-tetrabromoselenophene coproducts, so the mixture was used in the preparation of 14. The nbutyllithium (nominally 1.6 M in hexanes) was titrated with diphenylacetic acid in THF prior to use to determine its exact concentration.…”

Section: Methodsmentioning

confidence: 99%

Mixed-Metal Cluster Chemistry. 23. Synthesis and Crystallographic and Electrochemical Studies of Alkyne-Coordinated Group 6−Iridium Clusters Linked by Heterocyclic Groups

Notaras¹,

Lucas²,

Humphrey³

et al. 2003

Organometallics

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Reaction between the tetrahedral cluster compound Mo 2 Ir 2 (CO) 10 (η 5 -C 5 H 4 Me) 2 (1) and 2-iodo-5-(oct-1′-ynyl)thiophene afforded the pseudooctahedral cluster Mo 2 Ir 2 {µ 4 -η 2 -Me-(CH 2 ) 5 C 2 -5-C 4 H 2 S-2-I}(CO) 8 (η 5 -C 5 H 4 Me) 2 ( 17) by formal insertion of the alkyne CtC group into the Mo-Mo bond. Similar reactions of 1 or W 2 Ir 2 (CO) 10 (η 5 -C 5 H 4 Me) 2 (2) with heterocyclic di-or triynes afforded the related mono-, di-, or tricluster compounds [M 2 Ir 2 (CO) 8 (ηCompounds 27 and 29 correspond to the 1,2-dicluster adducts of the linear triyne Me(CH 2 ) 5 CtC-5-C 4 H 2 S-2-CtC-2-C 4 H 2 S-5-CtC(CH 2 ) 5 Me. No 1,3-dicluster isomer was isolated from direct reaction, but the molybdenum-containing 1,3-dicluster isomer was prepared by exploiting organic reaction chemistry on precoordinated functionalized alkyne ligands. Thus, Sonogashira coupling of 17 with trimethylsilylacetylene and subsequent desilylation gave Mo 2 Ir 2 {µ 4 -η 2 -Me(CH 2 ) 5 C 2 -5-C 4 H 2 S-2-CtCR}(CO) 8 (η 5 -C 5 H 4 Me) 2 [R ) SiMe 3 (18), H ( 19)]. Sonogashira coupling of 17 and 19 gave the 1,3-isomer [Mo 2 Ir 2 (CO) 8 (η 5 -C 5 H 4 -Me) 2 ] 2 {µ 8 -η 4 -Me(CH 2 ) 5 C 2 -2-C 4 H 2 S-5-CtC-2-C 4 H 2 S-5-C 2 (CH 2 ) 5 Me} (32), as well as the homocoupling product [Mo 2 Ir 2 (CO) 8 (η 5 -C 5 H 4 Me) 2 ] 2 {µ 8 -η 4 -Me(CH 2 ) 5 C 2 -2-C 4 H 2 S-5-CtCCtC-2-C 4 H 2 S-5-C 2 (CH 2 ) 5 Me} (33). The identities of 21, 29, and 31 were confirmed by single-crystal X-ray diffraction studies. Cyclic voltammetric scans for these complexes all show a reversible/ quasi-reversible oxidation followed by an irreversible oxidation process. Dicluster compounds linked by one heterocycle, and tricluster compounds, show two reduction processes, whereas dicluster compounds with longer bridges reveal only one reduction process.

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Section: Methodsmentioning

confidence: 99%

Mixed-Metal Cluster Chemistry. 23. Synthesis and Crystallographic and Electrochemical Studies of Alkyne-Coordinated Group 6−Iridium Clusters Linked by Heterocyclic Groups

Notaras¹,

Lucas²,

Humphrey³

et al. 2003

Organometallics

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“…To probe the mechanism of the oxidative rearrangement, we prepared 2-deutero 3-furfural ( 1- d 1 ) using the directed lithiation of Comins and co-workers (Scheme ) . The resulting organolithium was then quenched with D 2 O. , The deuterated product contained 80% deuterium incorporation, as determined by integration of the 1 H NMR spectrum.…”

Section: Resultsmentioning

confidence: 99%

Addition/Oxidative Rearrangement of 3-Furfurals and 3-Furyl Imines: New Approaches to Substituted Furans and Pyrroles

2008

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Furans and pyrroles are important synthons in chemical synthesis and are commonly found in natural products, pharmaceutical agents, and materials. Introduced herein are three methods to prepare 2-substituted 3-furfurals starting from 3-furfural, 3-bromofuran, and 3-vinylfurans. Addition of a variety of organolithium, Grignard, and organozinc reagents (M-R) to 3-furfural provides 3-furyl alcohols in high yields. Treatment of these intermediates with NBS initiates a novel oxidative rearrangement that results in the installation of the R group in the 2 position of the 2-substituted 3-furfurals. Likewise, metalation of 3-bromofuran with n-BuLi and addition to benzaldehyde provides a furyl alcohol that is converted to 2-phenyl 3-furfural upon oxidative rearrangement. Enantioenriched disubstituted furans can be prepared starting with the Sharpless asymmetric dihydroxylation of 3-vinylfurans. The resulting enantioenriched diols undergo the oxidative rearrangement to furnish enantioenriched 2-substituted 3-furfurals with excellent transfer of asymmetry. This later method has been applied to the enantioselective preparation of an intermediate in Honda's synthesis of the natural product (-)-canadensolide. Mechanistic studies involving deuterium-labeled furyl alcohol suggest that the oxidative rearrangement proceeds through an unsaturated 1,4-dialdehyde intermediate. The alcohol then cyclizes onto an aldehyde, resulting in the elimination of water and rearomatization. On the basis of this proposed mechanism, we found that 3-furyl imines undergo the addition of organometallic reagents to provide furyl sulfonamides. Under the oxidative rearrangement conditions, 2-substituted 3-formyl pyrroles are formed, providing a novel route to these heterocycles. In contrast to the metalation of heterocycles, which often lead to mixtures of regioisomeric products, these new oxidative rearrangements of furyl alcohols and furyl sulfonamides generate only one regioisomer in each case.

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“…Despite the long-standing use of this technique, a reliable and robust chemical shift standard is still an unmet need, as seen in a systematic error between separately reported 77 Se chemical shifts in the literature. [12] In the 77 Se NMR literature, chemical shift data are referenced to a relatively large number of compounds(seleninyl chloride, [13] dimethyl selenide, [14,15] selenophene, [16][17][18][19] diphenyl diselenide, [20][21][22][23][24] 4,4 0dimethyldiphenyl diselenide, [25] selenium oxide, [26] sodium selenite, [27] selenous acid). [13,[28][29][30][31] In addition, indication of the measurement parameters (concentration, ionic strength, temperature) is rather the exception than the case.…”

Section: Introductionmentioning

confidence: 99%

Selenate—An internal chemical shift standard for aqueous ⁷⁷Se NMR spectroscopy

Pálla

Herbath

Mazák

et al. 2021

Magnetic Reson in Chemistry

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The 77 Se NMR spectra of selenate were studied under various circumstances, such as concentration, pH, temperature, ionic strength, and D 2 O:H 2 O ratio, in order to examine its potential as a water-soluble internal chemical shift standard. The performance of selenate as a chemical shift reference and that of other attempted ones from the literature (dimethyl selenide, tetramethylsilane/TMS, and 3-(trimethylsilyl)propane-1-sulfonate/DSS) was also explored. The uncertainty in the resulting chemical shift relative to the effective spectral width is comparable to that of DSS. Compared to the currently prevalent water-soluble external chemical shift reference, selenic acid solution, the properties of internal selenate are much more favorable in terms of ease of use. We have also demonstrated that selenate can be used in reducing media, which is inevitable for the analysis of selenol compounds. Thus, it can be stated that sodium selenate is a robust internal chemical shift reference in aqueous media for 77 Se NMR measurements; the chemical shift of this reference in a solution containing 5 V/V% D 2 O at 25 C and 0.15 molÁdm À3 ionic strength is 1048.65 ppm relative to 60 V/V% dimethyl selenide in CDCl 3 and 1046.40 ppm relative to the 1 H signal of 0.03 V/V% TMS in CDCl 3 .In summary, a water-soluble, selenium-containing internal chemical shift reference compound was introduced for 77 Se NMR measurements for the first time in the literature, and with the aforementioned results all previous 77 Se measurements can be converted to a unified scale defined by the International Union of Pure and Applied Chemistry.

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Syntheses of Thiophenes with Group I Substituents

Cited by 6 publications

References 782 publications

Mixed-Metal Cluster Chemistry. 23. Synthesis and Crystallographic and Electrochemical Studies of Alkyne-Coordinated Group 6−Iridium Clusters Linked by Heterocyclic Groups

Mixed-Metal Cluster Chemistry. 23. Synthesis and Crystallographic and Electrochemical Studies of Alkyne-Coordinated Group 6−Iridium Clusters Linked by Heterocyclic Groups

Addition/Oxidative Rearrangement of 3-Furfurals and 3-Furyl Imines: New Approaches to Substituted Furans and Pyrroles

Selenate—An internal chemical shift standard for aqueous ⁷⁷Se NMR spectroscopy

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Syntheses of Thiophenes with Group I Substituents

Cited by 6 publications

References 782 publications

Mixed-Metal Cluster Chemistry. 23. Synthesis and Crystallographic and Electrochemical Studies of Alkyne-Coordinated Group 6−Iridium Clusters Linked by Heterocyclic Groups

Mixed-Metal Cluster Chemistry. 23. Synthesis and Crystallographic and Electrochemical Studies of Alkyne-Coordinated Group 6−Iridium Clusters Linked by Heterocyclic Groups

Addition/Oxidative Rearrangement of 3-Furfurals and 3-Furyl Imines: New Approaches to Substituted Furans and Pyrroles

Selenate—An internal chemical shift standard for aqueous 77Se NMR spectroscopy

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Selenate—An internal chemical shift standard for aqueous ⁷⁷Se NMR spectroscopy