Boraformylation and Silaformylation of Allenes

The boraformylation of allenes with B₂(pin)₂ and a formate ester as boron and formyl source, respectively, proceeds in the presence of a copper catalyst. The reaction selectively affords the corresponding β‐boryl β,γ‐unsaturated aldehydes in good to high yields. Furthermore, the silaformylation of allenes was achieved with a formate ester and PhMe₂Si−B(pin) as the silicon source.     

Experimental and Computational Exploration of para‐Selective Silylation with a Hydrogen‐Bonded Template

The regioselective conversion of C−H bonds into C−Si bonds is extremely important owing to the natural abundance and non‐toxicity of silicon. Classical silylation reactions often suffer from poor functional group compatibility, low atom economy, and insufficient regioselectivity. Herein, we disclose a template‐assisted method for the regioselective para silylation of toluene derivatives. A new template was designed, and the origin of selectivity was analyzed experimentally and computationally. An interesting substrate–solvent hydrogen‐bonding interaction was observed. Kinetic, spectroscopic, and computational studies shed light on the reaction mechanism. The synthetic significance of this strategy was highlighted by the generation of a precursor of a potential lipophilic bioisostere of γ‐aminobutyric acid (GABA), various late‐stage diversifications, and by mimicking enzymatic transformations.     

Rhodium(II)‐Catalyzed Dehydrogenative Silylation of Biaryl‐Type Monophosphines with Hydrosilanes

A rhodium‐catalyzed system is introduced for in situ modification of biaryl‐type monophosphines with hydrosilanes through a P^III‐chelation‐assisted dehydrogenative silylation reaction. A series of ligands containing silyl groups with different steric and electronic properties were obtained with excellent regioselectivities. This method offers many advantages, including the use of commercially available phosphines, no requirement for an external ligand or oxidant, a broader substrate scope, high efficiency, and access to a single regioisomer. Based on the outstanding properties of the parent scaffolds, the silyl‐substituted phosphines serve as excellent ligands in Pd‐catalyzed asymmetric Suzuki coupling reactions.     

Iron‐Catalyzed anti‐Selective Carbosilylation of Internal Alkynes

Reported is the anti ‐selective carbosilylation of internal alkynes with silylborane and alkyl halides using a FeBr₂/DPPE catalyst system. The iron catalyst allows simultaneous introduction of a carbon electrophile and a silicon nucleophile to simple internal alkynes, including diaryl‐, dialkyl‐, and aryl/alkyl‐substituted alkynes, in a highly stereoselective manner. Alkyl halides are applicable as the electrophiles, thereby enabling the synthesis of a variety of tetrasubstituted alkenylsilanes. In addition, syn ‐selective carbosilylation was achieved through stereoswitching, by using a silylborane having oxygen functionality on the silyl group. This novel iron‐catalyzed carbosilylation is a useful tool for expedient synthesis of stereodefined multisubstituted olefins, a fundamental structural motif in organic chemistry.