The metal-free B(C6F5)3 catalyzed dehydrocoupling of hydrosilanes with anilines, carbazoles and indoles is reported. For anilines and carbazoles the reaction proceeds by the liberation of H2 as the sole Si-N coupling byproduct. Indoles react with diphenyl(methyl) hydrosilane to give N-silyl indolines with high diastereoselectivity (d.r. 10 : 1) in excellent yields. A mechanism for this Si-N coupling/hydrogenation sequence is proposed.

The first frustrated Lewis pair-catalyzed cycloisomerization of a series of 1,5-enynes was developed. The reaction proceeds via the π-activation of the alkyne and subsequent 5-endo-dig cyclization with the adjacent alkene. The presence of PPh3 was of utmost importance on the one hand to prevent side reactions (for example, 1,1-carboboration) and on the other hand for the efficient protodeborylation to achieve the catalytic turnover. The mechanism is explained on the basis of quantum-chemical calculations, which are in full agreement with the experimental observations.

The frustrated Lewis pair (FLP)-catalyzed hydrogenation and deuteration of N-benzylidene-tert-butylamine (2) was kinetically investigated by using the three boranes B(C6F5)3 (1), B(2,4,6-F3-C6H2)3 (4), and B(2,6-F2-C6H3)3 (5) and the free activation energies for the H2 activation by FLP were determined. Reactions catalyzed by the weaker Lewis acids 4 and 5 displayed autoinductive catalysis arising from a higher free activation energy (2 kcal mol(-1)) for the H2 activation by the imine compared to the amine. Surprisingly, the imine reduction using D2 proceeded with higher rates. This phenomenon is unprecedented for FLP and resulted from a primary inverse equilibrium isotope effect.

The frustrated Lewis pair (FLP) mediated hydrosilylation of pentafulvenes is described yielding allyl silanes with high regioselectivity in excellent yields. While phenyl substituted allyl silanes undergo B(C6F5)3-mediated rearrangement to vinyl silanes, dimethyl derivatives experience FLP-catalyzed hydrogenation followed by an unprecedented protodesilylation. This observation allowed the metal-free hydrogenation of 6,6-dimethylfulvene to iso-propyl cyclopentene according to a FLP-catalyzed triple domino reaction consisting of hydrosilylation, hydrogenation and protodesilylation. The mechanisms were investigated by deuteration experiments.

No abstract

Die erste durch ein frustriertes Lewis-Paar katalysierte Cycloisomerisierung einer Reihe von 1,5-Eninen wurde entwickelt. Die Reaktion verläuft über die p-Aktivierung des Alkins mit anschließender 5-endo-dig-Cyclisierung.D ie Gegenwart von PPh 3 als Lewis-Base war von besonderer Bedeutung, um einerseits Nebenreaktionen zu unterdrücken (z. B. 1,1-Carboborierung) und um andererseits die Protodeborylierung für die katalytischeR eaktion zu erreichen. Der Mechanismus wurde durch quantenmechanischeR echnungen untersucht und ist im Einklang mit strukturchemischen und kinetischen Daten.

Dynamisch‐kovalente Chemie untersucht molekulare Austauschprozesse und führt zu zwei‐ oder dreidimensionalen Netzwerken kovalent‐organischer Materialien.

In den letzten fünf Jahren hat sich die Photoredoxkatalyse von einer Laborkuriosität zu einer verlässlichen Synthesemethode gemausert.