| Autor: |
von Grotthuss E; Institut für Anorganische und Analytische Chemie , Goethe-Universität Frankfurt , Max-von-Laue-Straße 7 , Frankfurt am Main D-60438 , Germany., Prey SE; Institut für Anorganische und Analytische Chemie , Goethe-Universität Frankfurt , Max-von-Laue-Straße 7 , Frankfurt am Main D-60438 , Germany., Bolte M; Institut für Anorganische und Analytische Chemie , Goethe-Universität Frankfurt , Max-von-Laue-Straße 7 , Frankfurt am Main D-60438 , Germany., Lerner HW; Institut für Anorganische und Analytische Chemie , Goethe-Universität Frankfurt , Max-von-Laue-Straße 7 , Frankfurt am Main D-60438 , Germany., Wagner M; Institut für Anorganische und Analytische Chemie , Goethe-Universität Frankfurt , Max-von-Laue-Straße 7 , Frankfurt am Main D-60438 , Germany. |
| Jazyk: |
angličtina |
| Zdroj: |
Journal of the American Chemical Society [J Am Chem Soc] 2019 Apr 10; Vol. 141 (14), pp. 6082-6091. Date of Electronic Publication: 2019 Mar 28. |
| DOI: |
10.1021/jacs.9b01998 |
| Abstrakt: |
Doubly reduced 9,10-dihydro-9,10-diboraanthracenes (DBAs) are introduced as catalysts for hydrogenation as well as hydride-transfer reactions. The required alkali metal salts M 2 [DBA] are readily accessible from the respective neutral DBAs and Li metal, Na metal, or KC 8 . In the first step, the ambiphilic M 2 [DBA] activate H 2 in a concerted, metal-like fashion. The rates of H 2 activation strongly depend on the B-bonded substituents and the counter cations. Smaller substituents (e.g., H, Me) are superior to bulkier groups (e.g., Et, pTol), and a Mes substituent is even prohibitively large. Li + ions, which form persistent contact ion pairs with [DBA] 2- , slow the H 2 -addition rate to a higher extent than more weakly coordinating Na + /K + ions. For the hydrogenation of unsaturated compounds, we identified Li 2 [4] (Me substituents at boron) as the best performing catalyst; its substrate scope encompasses Ph(H)C═N tBu, Ph 2 C═CH 2 , and anthracene. The conversion of E-Cl to E-H bonds (E = C, Si, Ge, P) was best achieved by using Na 2 [4]. The latter protocol provides facile access also to Me 2 Si(H)Cl, a most important silicone building block. Whereas the H 2 -transfer reaction regenerates the dianion [4] 2- and is thus immediately catalytic, the H - -transfer process releases the neutral 4, which has to be recharged by Na metal before it can enter the cycle again. To avoid Wurtz-type coupling of the substrate, the reduction of 4 must be performed in the absence of the element halide, which demands an alternating process management (similar to the industrial anthraquinone process). |
| Databáze: |
MEDLINE |
| Externí odkaz: |
|
