Chemistry:Trimethylsilyl isothiocyanate
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| Names | |
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| IUPAC name
isothiocyanato(trimethyl)silane[1]
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Other names
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| Identifiers | |
3D model (JSmol)
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PubChem CID
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| Properties | |
| C4H9NSSi | |
| Molar mass | 131.27 g·mol−1 |
| Density | 0.931 g·mL−1 [2] |
| Melting point | −32.8 °C (−27.0 °F; 240.3 K)[2] |
| Boiling point | 143 °C (289 °F; 416 K) |
| Reacts with water[3] | |
| Vapor pressure | 100 mmHg |
| Hazards | |
| Safety data sheet | External MSDS |
| GHS pictograms |     [4]
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| GHS Signal word | DANGER[4] |
| H226, H301, H311, H315, H319, H331, H334, H335 | |
| NFPA 704 (fire diamond) | |
| Flash point | 29 °C (84 °F; 302 K)[2] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Trimethylsilyl isothiocyanate (TMSNCS) is an organosilicon compound that contains an isothiocyanate whose nitrogen atom is covalently bonded to a trimethylsilyl group. The isothiocyanate group is an analog of the isocyanate group, but having a sulfur instead of oxygen.
Reactions
TMSNCS is useful reagent in organic chemistry. It is an ambident nucleophile, able to react with various alkyl halides, acetals, aldehydes, unsaturated compounds, aziridines, oxiranes, polycyclic aromatic hydrocarbons, and acetylated hexoses to form either thiocyanate or isothiocyanate structures.[6] As an electrophile, it can react with other nucleophiles to form thioamide types of structures, some of which can undergo subsequent reactions to form heterocycles.
Halide substitutions
As a sulfur nucleophile, TMSNCS substitutes for halides on a range of alkyl substrates, giving alkyl thiocyanates. These substitution reactions involve tetrabutylammonium fluoride used as phase-transfer catalyst and occur under particularly mild conditions.[7]
Reactions with aldehydes and acetals
As a nitrogen nucleophile, TMSNCS adds across the carbonyl group of aldehydes and substitutes isothiocyanate for one of the ether groups on acetals via acid-catalyzed processes.[8]
Mercapto-1,2,4-triazoles
A one-step method to prepare mercapto-1,2,4-tiazoles is favored on the industrial scale due to its high efficiency (88% yield) and non-constraining conditions: not requiring anhydrous solvent, inert gas temperature, or chromatographic purification. The method can be summarized as follows: after the equimolar mixture of benzohydrazide and TMSNCS reflux in the presence of EtOH for 5 hours, NaOH is added to the reaction mixture and the solution is refluxed for 4 h. Acetic acid is then used to cool and neutralize, ultimately yielding the pure white solid 3-phenyl-5-mercapto-4H-1,2,4-triazole at 88% yield.[6]
2-Amino-1,3,4-oxadiazoles
TMSNCS used for the synthesis of 2-amino-1,3,4-oxadiazoles. The TMSNCS reagent assists in the production of the thiosemicarbazide and the subsequent reaction (cyclodesulfurization of thiosemicarbazides under basic conditions in the presence of I2/KI) results in 2-amino-1,3,4-oxadiazoles in high yields (79–94%).[9] The 2-amino-1,3,4-oxadiazoles resulting from this reaction are: 2-Amino-5-phenyl-1,3,4-oxadiazole, 2-Amino-5-(p-methylphenyl)-1,3,4-oxadiazole, 2-Amino-5-(p-chlorophenyl)-1,3,4-oxadiazole, 2-Amino-5-(p-methoxyphenyl)- 1,3,4-oxadiazole, 2-Amino-5-(p-nitrophenyl) -1,3,4-oxadiazole, 2-Amino-5-(o-methylphenyl)-1,3,4-oxadiazole, 2-Amino-5-(o-chlorophenyl)-1,3,4-oxadiazole, ect.[10]
Notes
- ↑ "Trimethylsilyl isothiocyanate (Compound)". https://pubchem.ncbi.nlm.nih.gov/compound/Trimethylsilyl-isothiocyanate#section=UN-GHS-Classification. Retrieved April 9, 2020.
- ↑ 2.0 2.1 2.2 "(Trimethylsilyl)isothiocyanate". https://www.sigmaaldrich.com/catalog/product/aldrich/230766?lang=en®ion. Retrieved April 9, 2020.
- ↑ "Trimethylsilyl isothiocyanate, 94%". Thermo Fisher Scientific. https://www.alfa.com/en/catalog/L03277/. Retrieved April 9, 2020.
- ↑ 4.0 4.1 "Trimethylsilyl isothiocyanate". European Chemicals Agency (ECHA). https://echa.europa.eu/information-on-chemicals/cl-inventory-database/-/discli/details/62361. Retrieved April 9, 2020.
- ↑ "Safety Data Sheet". Thermo Fisher Scientific. https://www.alfa.com/en/msds/?language=EN&subformat=AGHS&sku=L03277. Retrieved April 10, 2020.
- ↑ 6.0 6.1 Guda, Dinneswara Reddy; Wang, Tengjiao; Cho, Hyeon Mo; Lee, Myong Euy (September 2012). "Trimethylsilyl isothiocyanate (TMSNCS): an efficient reagent for the one-pot synthesis of mercapto-1,2,4-triazoles". Tetrahedron Letters 53 (39): 5238. doi:10.1016/j.tetlet.2012.07.054. https://www.sciencedirect.com/science/article/pii/S0040403912012294.
- ↑ Renard, Pierre-Yves; Schwebel, Hervé; Vayron, Philippe; Leclerc, Eric; Dias, Sonia; Mioskowski, Charles (2001). "Optimized access to alkyl thiocyanates". Tetrahedron Lett. 42 (48): 8479–8481. doi:10.1016/S0040-4039(01)01846-9.
- ↑ Nishiyama, Kozaburo; Oba, Makoto (June 1987). "Reactions of Trimethylsilyl Isothiocyanate with Aldehydes and Acetals. Synthesis of Symmetrically and Unsymmetrically Isothiocyanato-Substituted Ethers". Bulletin of the Chemical Society of Japan 60 (6): 2289–2291. doi:10.1246/bcsj.60.2289.
- ↑ Guda, Dinneswara Reddy; Cho, Hyeon Mo; Lee, Myong Euy (2013). "Mild and convenient one-pot synthesis of 2-amino-1,3,4-oxadiazoles promoted by trimethylsilyl isothiocyanate (TMSNCS)". RSC Advances 3 (21): 7684. doi:10.1039/C3RA41044G. Bibcode: 2013RSCAd...3.7684G. https://pubs.rsc.org/en/content/articlelanding/2013/ra/c3ra41044g. Retrieved 10 April 2020.
- ↑ Guda, Dinneswara Reddy; Cho, Hyeon Mo; Lee, Myong Euy (2013). "Electronic Supplementary Information (ESI)". The Royal Society of Chemistry: S1–S8. http://www.rsc.org/suppdata/ra/c3/c3ra41044g/c3ra41044g.pdf. Retrieved 10 April 2020.
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