Practical and scalable synthesis of bench-stable organofluorosilicate salts.

Silanes have enjoyed significant success as synthetic tools in the last few decades. In many of the reactions that use silanes, a pentacoordinate silicate is proposed as the reactive intermediate. Despite this, there is no general method to synthesize pentacoordinate fluorosilicates and use them as reagents instead of organo- or alkoxysilanes.

Formal Asymmetric Hydrobromination of Styrenes Copper-Catalyzed 1,3-Halogen Migration.

An enantioselective Cu(I)-catalyzed 1,3-halogen migration reaction accomplishes a formal hydrobromination by transferring a bromine activating group from a sp carbon to a benzylic carbon in good and with concomitant borylation of the Ar-Br bond. Computational modelling aids in understanding the reaction outcome and suggests future directions to improve the formal asymmetric hydrobromination. The benzyl bromide can be displaced with a variety of nucleophiles to produce a wide array of functionalized products.

Mechanistic studies of copper(I)-catalyzed 1,3-halogen migration.

An ongoing challenge in modern catalysis is to identify and understand new modes of reactivity promoted by earth-abundant and inexpensive first-row transition metals. Herein, we report a mechanistic study of an unusual copper(I)-catalyzed 1,3-migration of 2-bromostyrenes that reincorporates the bromine activating group into the final product with concomitant borylation of the aryl halide bond. A combination of experimental and computational studies indicated this reaction does not involve any oxidation state changes at copper; rather, migration occurs through a series of formal sigmatropic shifts.

1,3-Halogen migration as an entry to aryl coppers from an unintuitive starting material.

A copper(I) catalyzed 1,3-halogen migration/borylation migrates a bromine from an sp(2) carbon to a benzylic carbon with concomitant borylation of the aryl-bromine bond. This transformation proceeds via an aryl copper intermediate which can be accessed independently and then trapped with electrophiles. As such, copper-catalyzed 1,3-halogen migration provides unique and mild access to an aryl copper species that allows for rapid aromatic functionalization from an unconventional starting material.

Investigation of the mechanism for the preparation of 6-phenyl-2,4-dioxotetrahydropyrans by the potassium carbonate promoted condensation between acetoacetate esters and benzaldehyde.

Treatment of benzaldehyde and an acetoacetate ester with potassium carbonate in an alcohol solvent proceeds via γ-C-alkylation rather than α-C-alkylation resulting in the formation of 6-phenyl-2,4-dioxotetrahydropyran. Based upon results from deuterium exchange experiments, carbon-13 labeling experiments, (1)H NMR monitoring studies, and reactivity studies, our proposed mechanism for this reaction involves deprotonation at the α-carbon, intramolecular proton transfer to form a γ-anion, addition of the resulting γ-anion to the carbonyl carbon of benzaldehyde, and intramolecular transesterification.

Copper-catalyzed recycling of halogen activating groups via 1,3-halogen migration.

A Cu(I)-catalyzed 1,3-halogen migration reaction effectively recycles an activating group by transferring bromine or iodine from a sp(2) to a benzylic carbon with concomitant borylation of the Ar-X bond. The resulting benzyl halide can be reacted in the same vessel under a variety of conditions to form an additional carbon-heteroatom bond. Cross-over experiments using an isotopically enriched bromide source support intramolecular transfer of Br.

Beyond benzyl grignards: facile generation of benzyl carbanions from styrenes.

Benzylic functionalization is a convenient approach towards the conversion of readily available aromatic hydrocarbon feedstocks into more useful molecules. However, the formation of carbanionic benzyl species from benzyl halides or similar precursors is far from trivial. An alternative approach is the direct reaction of a styrene with a suitable coupling partner, but these reactions often involve the use of precious-metal transition-metal catalysts.