Palladium-Catalyzed Silylacylation of Allenes Using Acylsilanes

Recent developments in difunctionalization of unsaturated hydrocarbons with organosilicon reagents

Organosilicon compounds have attracted considerable attention because of their special biological activities. Direct difunctionalization of unsaturated hydrocarbons with organosilicon reagents for the efficient construction of synthetically valuable silicon-functionalized compounds are featured with a high step and atom economy, which could form carbon-silicon/carbon-carbon bonds or carbon-silicon/carbon-hetero bonds in one step. This review summarizes the recent advances on this topic based on different unsaturated hydrocarbons along with typical examples and mechanisms.

Benzocyclobutenone synthesis exploiting acylsilanes as photofunctional directing groups

The visible-light irradiation of acylsilane tethered vinyl ketones promotes an intramolecular Stetter-type reaction via siloxycarbene intermediates. To exploit this unique mode of reactivity, we herein describe the innovative use of acylsilanes as photofunctional directing groups. First, an acylsilane directed ruthenium catalysed C-H olefination reaction was developed to generate benzoylsilanes bearing vinyl ketone functionality. Then, visible-light irradiation initiated the 1,4-conjugate addition of transient siloxycarbene intermediates with pendent vinyl ketones to afford unique benzocyclobutenone scaffolds primed for further synthetic elaboration.

The role of silicon in drug discovery: a review

This review aims to highlight the role of silicon in drug discovery. Silicon and carbon are often regarded as being similar with silicon located directly beneath carbon in the same group in the periodic table. That being noted, in many instances a clear dichotomy also exists between silicon and carbon, and these differences often lead to vastly different physiochemical and biological properties. As a result, the utility of silicon in drug discovery has attracted significant attention and has grown rapidly over the past decade. This review showcases some recent advances in synthetic organosilicon chemistry and examples of the ways in which silicon has been employed in the drug-discovery field.

Palladium-Catalyzed Addition of Trifluoroacetylsilanes to Alkenes and Allenes via the Cleavage of C-Si Bonds

The palladium-catalyzed addition of trifluoroacetylsilanes to alkenes and allenes via the cleavage of the C-Si bonds is reported. When alkenes are used, cyclopropanation occurs to afford cyclopropane derivatives bearing CF3 and siloxy groups with a high degree of stereoselectivity. When allenes are used, silylacylation occurs to form alkenylsilane derivatives bearing a trifluoroacetyl group at the allylic position with complete regioselectivity. Both reactions allow for highly atom-economical access to densely functionalized fluorinated organosilane derivatives using simple building blocks.

Acylsilanes in Transition-Metal-Catalyzed and Photochemical Reactions: Clarifying Product Formation

Acylsilanes are able to react as nucleophilic carbene precursors, electrophiles, and directing groups in C-H functionalization. To date, some of the products reportedly formed during transition-metal-catalyzed and photochemical reactions involving acylsilanes have been incorrectly assigned. To provide clarity, we herein address these structural misassignments and detail the revised structures. New insights into the reactivity of acylsilanes were also afforded via the discovery that light-induced siloxy carbenes participate in intramolecular 1,2-carbonyl addition to proximal esters.

Pd-Catalyzed Regioselective Cyclopropanation of 2-Substituted 1,3-Dienes

A Pd-catalyzed 3,4-regioselective cyclopropanation of 2-substituted 1,3-dienes by decomposition of diazo esters is reported. The vinylcyclopropanes generated are isolated in practical chemical yields with high levels of regioselectivity but low diastereoselectivity. The system operates under mild reaction conditions, is scalable, and tolerates various sensitive functional groups. A series of original postcatalytic derivatizations is presented to highlight the synthetic potential of the catalytic method.

Bimetallic tandem catalysis-enabled enantioselective cycloisomerization/carbonyl-ene reaction for construction of 5-oxazoylmethyl α-silyl alcohol

A bimetallic tandem catalysis-enabled enantioselective cycloisomerization/carbonyl-ene reaction was developed. The reaction proceeded well with a broad range of N-propargylamides and acylsilanes, affording the target chiral 5-oxazoylmethyl α-silyl alcohols in up to 95% yield and 99% ee under mild conditions. Importantly, this facile protocol was available for the late-stage modification of several bioactive molecules. Based on the mechanistic study and control experiments, a possible catalytic cycle and transition state are proposed to elucidate the reaction process and enantioinduction.

Palladium-catalyzed addition of acylsilanes across alkynes via the activation of a C-Si bond

Palladium-catalyzed addition of a C-Si bond in acylsilanes across the triple bonds in an alkyne bearing a carbonyl group at one terminal is reported. The reaction proceeds with excellent regioselectivity, in which a silyl group is incorporated into the carbon α to the carbonyl group, allowing for straightforward access to a variety of functionalized alkenylsilane derivatives. Catalytic synthesis of indanones by annulation between acylsilanes and alkynes with an identical catalytic system is also reported.

Light-Promoted Arylsilylation of Alkenes with Hydrosilanes

Herein, we report light-promoted photo/hydrogen atom transfer dual catalysis for arylsilylation of alkenes via the radical-radical cross-coupling with diverse hydrosilanes, which provides a simple and efficient method to prepare various organosilicon compounds with a wide range of substrate scope and good functional group tolerance under transition-metal- and chemical-oxidant-free conditions. Furthermore, the arylsilylation of alkenes can also proceed via the possible electron donor-acceptor complex under exogenous photocatalyst-free conditions.

Cobalt-catalysed acyl silane directed ortho C–H functionalisation of benzoyl silanes

Acyl silanes can be engaged as weakly coordinating directing groups in cobalt catalysed C–H functionalisation reactions to prepare benzoyl silanes that are highly amenable to subsequent synthetic manipulations yet inaccessible via existing methods.