Unveiling the Takai Olefination Reagent via Tris(tert-butoxy)siloxy Variants
| Autor: | Reiner Anwander, Daniel Werner |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Tris
Takai olefination 010405 organic chemistry Tert-butoxy General Chemistry 010402 general chemistry 01 natural sciences Biochemistry Medicinal chemistry Catalysis 0104 chemical sciences Benzaldehyde chemistry.chemical_compound Colloid and Surface Chemistry chemistry Nucleophile Reagent Moiety Selectivity |
| Zdroj: | Journal of the American Chemical Society. 140:14334-14341 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | The elusive Takai olefination reagent, namely, the iodo-methylidene Cr(III) complex [Cr2Cl4(CHI)(thf)4], has been isolated by careful handling of the reaction between CrCl2 and CHI3 in THF at −35 °C. Alternatively, treatment of [Cr(OSi(OtBu)3)2] with CHI3 gave the mixed-valent dihalido-methanide complex [CrII/III2I2(OSi(OtBu)3)2(CHI2)], featuring a Cr(III)–CHI2 moiety. In the presence of TMEDA nucleophilic attack at CHI2 occurred generating the zwitterionic species [CrIII(OSi(OtBu)3)2(tmeda-CHI)][I]. Complexes [Cr2Cl4(CHI)(thf)4] and [CrII/III2I2(OSi(OtBu)3)2(CHI2)] were screened for their ability to induce monohalido olefination of benzaldehyde. Remarkably, both complexes promote olefination, with [Cr2Cl4(CHI)(thf)4] accomplishing the same E selectivity as Takai’s original mixture. Complex [CrII/III2I2(OSi(OtBu)3)2(CHI2)], however, appeared to give preferentially Z isomer, corroborating the monoiodo-methylidene species Cr(III)–CHI–Cr(III) as the active olefination component of the original in situ genera... |
| Databáze: | OpenAIRE |
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