Aryne cycloaddition reactions of benzodioxasilines as aryne precursors generated by catalytic reductive ortho-C-H silylation of phenols with traceless acetal directing groups

Recent Progress in Transition Metal-Catalyzed Hydrosilanes-Mediated C-H Silylation

Organosilicon compounds are widely used in materials science, medicinal chemistry and synthetic chemistry. Recently, significant progress has been achieved in transition metal-catalyzed dehydrogenative C-H silylation. Particularly, recently developed monohydrosilane and dihydrosilane mediated C-H silylation have emerged as powerful tools in constructing C-Si bonds. Besides, dihydrosilane-mediated enantioselective asymmetric C-H silylation has successfully achieved the construction of central and helical silicon chirality. In addition, chiral organosilicon compounds have exhibited excellent photoelectric material properties and broad application prospects. Furthermore, organosilicon compounds could under a series of functional group transformations to enrich the diversity of silicon chemistry. This review will present a comprehensive picture of the development of transition metal-catalyzed hydrosilanes-mediated intramolecular C(sp 2 )-H and C(sp 3 )-H silylation organized by their reaction types and mechanisms. In addition, dihydrosilane-mediated enantioselective asymmetric C-H silylation to construct central and helical silicon chirality will also be highlighted in the review.

Cyclic Diaryl λ3-Bromanes: A Rapid Access to Molecular Complexity via Cycloaddition Reactions

Biaryls have widespread applications in organic synthesis. However, sequentially polysubstituted biaryls are underdeveloped due to their challenging preparation. Herein, we report the synthesis of dissymetric 2,3,2',3',4-substituted biaryls via pericyclic reactions of cyclic diaryl λ³-bromanes. The functional groups tolerance and atom economy allow access to molecular complexity in a single reaction step. Continuous flow protocol has been designed for the scale-up of the reaction, while postfunctionalizations have been developed taking advantage of the residual Br-atom.

A simple Hückel model-driven strategy to overcome electronic barriers to retro-Brook silylation relevant to aryne and bisaryne precursor synthesis

ortho-Silylaryl triflate precursors (oSATs) have been responsible for many recent advances in aryne chemistry and are most commonly accessed from the corresponding 2-bromophenol. A retro-Brook O- to C-silyl transfer is a key step in this synthesis but not all aromatic species are amenable to the transformation, with no functionalized bisbenzyne oSATs reported. Simple Hückel models are presented which show that the calculated aromaticity at the brominated position is an accurate predictor of successful retro-Brook reaction, validated synthetically by a new success and a predicted failure. From this, the synthesis of a novel difunctionalized bisaryne precursor has been tested, requiring different approaches to install the two C-silyl groups. The first successful use of a disubstituted o-silylaryl sulfonate bisbenzyne precursor in Diels-Alder reactions is then shown.

Rapid Synthesis of Alkenylated BINOL Derivatives via Rh(III)-Catalyzed C-H Bond Activation

Modification of BINOL units has been well examined via Rh-catalyzed C-H activation and functionalization reactions by using ester carbonyls as directing groups and alkenes as coupling partners. The one-pot strategy was an efficient protocol for the rapid synthesis of BINOL derivatives with retention of optical purity.

Ruthenium-Catalyzed Site-Selective Intramolecular Silylation of Primary C-H Bonds for Synthesis of Sila-Heterocycles

Incorporating the silicon element into bioactive organic molecules has received increasing attention in medicinal chemistry. Moreover, organosilanes are valuable synthetic intermediates for fine chemicals and materials. Transition metal-catalyzed C-H silylation has become an important strategy for C-Si bond formations. However, despite the great advances in aromatic C(sp²)-H bond silylations, catalytic methods for aliphatic C(sp³)-H bond silylations are relatively rare. Here we report a pincer ruthenium catalyst for intramolecular silylations of various primary C(sp³)-H bonds adjacent to heteroatoms (O, N, Si, Ge), including the first intramolecular silylations of C-H bonds α to O, N, and Ge. This method provides a general, synthetically efficient approach to novel classes of Si-containing five-membered [1,3]-sila-heterocycles, including oxasilolanes, azasilolanes, disila-heterocycles, and germasilolane. The trend in the reactivity of five classes of C(sp³)-H bonds toward the Ru-catalyzed silylation is elucidated. Mechanistic studies indicate that the rate-determining step is the C-H bond cleavage involving a ruthenium silyl complex as the key intermediate, while a η²-silene ruthenium hydride species is determined to be an off-cycle intermediate.