| Autor: |
Krautwald S; Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States., Bezdek MJ; Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States., Chirik PJ; Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States. |
| Jazyk: |
angličtina |
| Zdroj: |
Journal of the American Chemical Society [J Am Chem Soc] 2017 Mar 15; Vol. 139 (10), pp. 3868-3875. Date of Electronic Publication: 2017 Mar 01. |
| DOI: |
10.1021/jacs.7b00445 |
| Abstrakt: |
A cobalt-catalyzed method for the 1,1-diboration of terminal alkynes with bis(pinacolato)diboron (B 2 Pin 2 ) is described. The reaction proceeds efficiently at 23 °C with excellent 1,1-selectivity and broad functional group tolerance. With the unsymmetrical diboron reagent PinB-BDan (Dan = naphthalene-1,8-diaminato), stereoselective 1,1-diboration provided products with two boron substituents that exhibit differential reactivity. One example prepared by diboration of 1-octyne was crystallized, and its stereochemistry established by X-ray crystallography. The utility and versatility of the 1,1-diborylalkene products was demonstrated in a number of synthetic applications, including a concise synthesis of the epilepsy medication tiagabine. In addition, a synthesis of 1,1,1-triborylalkanes was accomplished through cobalt-catalyzed hydroboration of 1,1-diborylalkenes with HBPin. Deuterium-labeling and stoichiometric experiments support a mechanism involving selective insertion of an alkynylboronate to a Co-B bond of a cobalt boryl complex to form a vinylcobalt intermediate. The latter was isolated and characterized by NMR spectroscopy and X-ray crystallography. A competition experiment established that the reaction involves formation of free alkynylboronate and the two boryl substituents are not necessarily derived from the same diboron source. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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