Synthese funktioneller Silyltriflate auf der Basis von Allylsilanen

Enantioselective and Regiodivergent Synthesis of Propargyl- and Allenylsilanes through Catalytic Propargylic C-H Deprotonation

We report a highly enantioselective intermolecular C-H bond silylation catalyzed by a phosphoramidite-ligated iridium catalyst. Under reagent-controlled protocols, propargylsilanes resulting from C(sp3)-H functionalization, as well the regioisomeric and synthetically versatile allenylsilanes, could be obtained with excellent levels of enantioselectivity and good to excellent control of propargyl/allenyl selectivity. In the case of unsymmetrical dialkyl acetylenes, good to excellent selectivity for functionalization at the less-hindered site was also observed. A variety of electrophilic silyl sources (R3SiOTf and R3SiNTf2), either commercial or in situ-generated, were used as the silylation reagents, and a broad range of simple and functionalized alkynes, including aryl alkyl acetylenes, dialkyl acetylenes, 1,3-enynes, and drug derivatives were successfully employed as substrates. Detailed mechanistic experiments and DFT calculations suggest that an η3-propargyl/allenyl Ir intermediate is generated upon π-complexation-assisted deprotonation and undergoes outer-sphere attack by the electrophilic silylating reagent to give propargylic silanes, with the latter step identified as the enantiodetermining step.

The First Coordination Polymers Based on 1,3-Diphosphaferrocenes and 1,1',2,3',4-Pentaphosphaferrocenes

Phosphaferrocenes in combination with coinage metal salts proved to be excellent building blocks in supramolecular chemistry for the buildup of oligomeric and polymeric assemblies. The synthesis of a series of novel phosphaferrocenes containing the 1,3‐P₂C₃iPr₃ and/or the 1,2,4‐P₃C₂iPr₂ ligand is described herein. The self‐assembly processes of the 1,3‐diphospha‐, 1,2,4‐triphospha‐, and 1,1′,2,3′,4‐pentaphosphaferrocenes with Cu^I halides led to the formation of 1D or 2D polymers. With [Cp*Fe(η⁵‐P₂C₃iPr₃)] (Cp* = η⁵‐C₅Me₅), infinite chains are formed, whereas with [(η⁵‐P₃C₂iPr₂)Fe(η⁵‐P₂C₃iPr₃)] 1D ladderlike structures are obtained. These are the first polymers containing such a di‐ and pentaphosphaferrocene, respectively. On the other hand, the use of [Cp*Fe(η⁵‐P₃C₂iPr₂)] leads to the construction of 2D networks with intact sandwich complexes, which is uncommon for this class of complexes.

The First Example of Nickel-Catalyzed Silyl-Heck Reactions: Direct Activation of Silyl Triflates Without Iodide Additives

For the first time, nickel-catalyzed silyl-Heck reactions are reported. Using simple phosphine-supported nickel catalysts, direct activation of silyl triflates has been achieved. These results contrast earlier palladium-catalyzed systems, which require iodide additives to activate silyl-triflates. These nickel-based catalysts exhibit good functional group tolerance in the preparation of vinyl silanes, and unlike earlier systems, allows for the incorporation of trialkylsilanes larger than Me₃Si.

Strained organosilacyclic compounds: synthesis of anti-Bredt olefins and trans-dioxasilacyclooctenes

Insertions of silylenes into the allylic carbon-oxygen bond of vinyl epoxides was shown to generate 1,2-silaoxetanes. These intermediates undergo highly diastereoselective additions to aldehydes to form anti-Bredt olefins and trans-dioxasilacyclooctenes. Additions of electrophiles could be performed selectively on the outside face of these strained trans-cycloalkenes to provide valuable functionalized compounds.

Application of Directed Orthometalation toward the Synthesis of Aryl Siloxanes

A selection of ortho-substituted aryl siloxanes have been prepared by directed orthometalation protocols. These siloxanes can be prepared in high yields and purity by use of a diverse selection of ortho-directing groups and electrophilic siloxane derivatives. The siloxanes are employed in palladium-catalyzed cross-coupling reactions with aryl bromides to generate unsymmetrical ortho-substituted biaryls in good to excellent yields.