Addition of Silicon−Silicon σ-Bonds to Arynes or Bisarynes Catalyzed by a Palladium Complex

Synthesis, characterisation and electronic properties of naphthalene bridged disilanes

Synthesis of naphthalene bridged disilanes 2_R (R = Me, Ph) was performed via catalytic dehydrocoupling. Using RhCl(PPh₃)₃ as a catalyst, an intramolecular Si-Si bond was readily formed from the corresponding disilyl precursors 1_R (R = Me, Ph). For catalytic reactions using (C₆F₅)₃B(OH₂), bridged siloxanes (3_Ph and 3_Me) were observed. Attempts to install the 1,8-naphthalene bridge directly onto a disilane resulted in an unusual product (4), containing two silicon centres bridged through one naphthyl group, and another naphthyl group attached to a single Si centre. In order for this product to form, both a Si to Si hydrogen shift rearrangement as well as Si-Si bond cleavage occurred. The effects of phenyl and methyl substitutions on the structure and electronic properties of the synthesised compounds was investigated by single crystal X-ray diffraction, as well as IR and multinuclear NMR spectroscopic analysis. In addition, theoretical UV-Vis absorption maxima were evaluated using density functional theory (TD-SCF) on a B3LYP/6-31(++)G** level of theory and compared with experimental UV-Vis spectroscopic data.

Dimethyl 4,4′-(dimethylsilanediyl)dibenzoate

The complete molecule of the title compound, C18H20O4Si, is generated by crystallographic twofold symmetry, with the Si atom lying on the rotation axis. The molecule adopts a V-shape: the dihedral angle between the benzene ring and it attached methyl formate unit is 9.3 (2)°, and the dihedral angle between the benzene rings is 68.8 (1)°. In the crystal, weak C—H...O hydrogen bonds link the molecules into [101] chains.

Copper Catalysis for Synthesizing Main-Group Organometallics Containing B, Sn or Si

A copper complex has proven to be a potent catalyst for forming a C-B bond via diborylation of arynes and alkynes, affording vic-diborylarenes and vic-diborylalkenes with high efficiency. A boryl-substituted organocopper species, which is intermediately generated in the diborylation, has been found to be captured by a tin or a carbon electrophile, leading to three-component borylstannylation or carboboration, in which C-B and C-Sn (or C) bonds are constructed simultaneously. Furthermore, reducing the Lewis acidity of the boron center with 1,8-diaminonaphthalene decisively alters the regiochemical behavior of the borylcopper species, enabling the installation of a boryl moiety to occur at an internal carbon of terminal alkynes in borylstannylation and protoboration. Copper catalysis for C-Sn and C-Si bond-forming processes via distannylation, hydrostannylation and silylstannylation, as well as silver catalysis for a C-B bond-forming reaction, is also described.

Reaction of arynes with sulfoxides

A S-O bond insertion reaction of sulfoxides with arynes is reported. This reaction represents a rare instance of semipolar single bond insertion in aryne chemistry. The study of mechanism indicates that a sulfur ylide triggered by aryne is the key intermediate, which further transfers its methylene group to carbonyl compounds to give epoxides and thioethers through a sequential process.

Palladium-catalyzed annulation of arynes by o-halobenzamides: synthesis of phenanthridinones

The palladium-catalyzed annulation of arynes by substituted o-halobenzamides produces N-substituted phenanthridinones in good yields. This methodology provides this important heterocyclic ring system in a single step by simultaneous C-C and C-N bond formation, under relatively mild reaction conditions, and tolerates a variety of functional groups.

Copper-catalysed bromoalkynylation of arynes

Arynes were found to be inserted into a C(sp)-Br sigma-bond of bromoalkynes in the presence of a copper catalyst, giving (alkynyl)bromoarenes in a straightforward manner.

Synthesis of 9-fluorenylidenes and 9,10-phenanthrenes through palladium-catalyzed aryne annulation by o-halostyrenes and o-halo allylic benzenes

A number of functionally substituted 9-fluorenylidenes and 9,10-phenanthrenes have been synthesized from substituted o-halostyrenes and o-halo allylic benzenes respectively in good yields by the palladium-catalyzed annulation of arynes. The methodology tolerates a variety of functional groups, including cyano, ester, aldehyde, and ketone groups, occurs under relatively mild reaction conditions, and involves the generation of two new carbon-carbon bonds, thus providing these important carbocyclic ring systems in a single synthetic step.

Synthesis of transition metal isocyanide compounds from carbonyl complexes via reaction with Li[Me3SiNR]

The reaction between a transition metal carbonyl compound, L(n)MCO, and Li[Me(3)SiNR] yields the corresponding isocyanide derivative, L(n)MCNR, thereby providing a new route to transition metal isocyanide compounds that does not require the use of free isocyanides as reagents.

Palladium-catalyzed synthesis of 9-fluorenylidenes through aryne annulation

The palladium-catalyzed annulation of arynes by substituted o-halostyrenes produces substituted 9-fluorenylidenes in good yields. This methodology provides this important carbocyclic ring system in a single step, which involves the generation of two new carbon-carbon bonds, occurs under relatively mild reaction conditions, and tolerates a variety of functional groups, including cyano, ester, aldehyde, and ketone groups.

Design and synthesis of isocyanide ligands for catalysis: application to Rh-catalyzed hydrosilylation of ketones

New isocyanide ligands with meta-terphenyl backbones were synthesized. 2,6-Bis[3,5-bis(trimethylsilyl)phenyl]-4-methylphenyl isocyanide exhibited the highest rate acceleration in rhodium-catalyzed hydrosilylation among other isocyanide and phosphine ligands tested in this study. 1H NMR spectroscopic studies on the coordination behavior of the new ligands to [Rh(cod)2]BF4 indicated that 2,6-bis[3,5-bis(trimethylsilyl)phenyl]-4-methylphenyl isocyanide exclusively forms the biscoordinated rhodium-isocyanide complex, whereas less sterically demanding isocyanide ligands predominantly form tetracoordinated rhodium-isocyanide complexes. FTIR and 13C NMR spectroscopic studies on the hydrosilylation reaction mixture with the rhodium-isocyanide catalyst showed that the major catalytic species responsible for the hydrosilylation activity is the Rh complex coordinated with the isocyanide ligand. DFT calculations of model compounds revealed the higher affinity of isocyanides for rhodium relative to phosphines. The combined effect of high ligand affinity for the rhodium atom and the bulkiness of the ligand, which facilitates the formation of a catalytically active, monoisocyanide-rhodium species, is proposed to account for the catalytic efficiency of the rhodium-bulky isocyanide system in hydrosilylation.

Insertion of arynes into carbon–halogen σ-bonds: regioselective acylation of aromatic rings

Arynes were found to insert into carbon-halogen sigma-bonds of various acid halides, enabling acyl and halogen moieties to be introduced simultaneously into adjacent positions of aromatic rings.

Palladium-Catalyzed Distannylation of ortho-Quinodimethanes

An exo-diene moiety of various ortho-quinodimethanes, regardless of its transient character, was inserted into a Sn-Sn sigma-bond of hexabutyldistannane in the presence of a palladium catalyst, giving alpha,alpha'-bis(tributylstannyl)-o-xylenes straightforwardly.

Palladium-catalysed dimerisation–distannylation of arynes: synthesis and reaction of 2,2′-distannylbiaryls

Two molar amounts of arynes were found to insert into a Sn-Sn bond of a distannane in the presence of a sub-stoichiometric amount of a palladium-phosphite complex, affording straightforwardly 2,2'-distannylbiaryls.

Aminosilylation of arynes with aminosilanes: synthesis of 2-silylaniline derivatives

The nitrogen-silicon sigma-bond of aminosilanes added across the triple bond of arynes to give varied 2-silylaniline derivatives straightforwardly.

Facile insertion reaction of arynes into carbon–carbon σ-bonds

The carbon-carbon sigma-bond of various beta-dicarbonyl compounds was found to add to the triple bond of arynes under extremely mild conditions, leading to direct introduction of different carbon functional groups into the aromatic skeletons.