Synthesis of Enantioenriched α,α-Difluoro-β-arylbutanoic Esters by Pd-Catalyzed Asymmetric Hydrogenation

Palladium-catalyzed asymmetric hydrogenation of lactones under base-free conditions

Asymmetric hydrogenation of esters through homogeneous catalysis is a significantly important transformation in organic synthesis. The systems developed so far mainly focused on chiral iridium and ruthenium catalysts, which required a base to facilitate the activity. Herein, we present a palladium-catalyzed asymmetric hydrogenation of lactones under base-free conditions through dynamic kinetic resolution and kinetic resolution. The reaction exhibits high enantioselectivity and excellent functional group tolerance. Remarkably, the hydrogenation proceeds smoothly at the gram scale, and the products can be transformed into several chiral potential building blocks without loss of optical purity. This work provides a new strategy for asymmetric hydrogenation of esters under base-free conditions.

Squaramide/Li+-Catalyzed Direct SN1-Type Reaction of Vinyl Triflates with Difluoroenoxysilanes through Vinyl Cations

Difluoromethylene-skipped enones have been readily obtained from arylvinyltriflates and aryldifluoroenoxysilanes. While these useful compounds are difficult to synthesize by the classical aldol/dehydration approach, the use of a squaramide/Li⁺ catalyst allows their direct formation via a vinyl carbocation paired with a weakly coordinating perfluorinated alkoxyaluminate. This strategy makes possible a reaction between a typically weak electrophile and a weak nucleophile. Control experiments and DFT computations shed light on the mechanism of this transformation.

Radical Esterification of Unactivated Alkenes Using Formate as Carbonyl Source

In recent years, methyl formate has received considerable attention as an ideal and green C1 building block to synthesize carboxylic esters. However, examples of a one-step route to esters with one-carbon elongation using methyl formate as a source of methoxycarbonyl radical are still rare. Herein, we present peroxide-induced radical carbonylation of N-(2-methylallyl)benzamides with methyl formate as the precursor of methoxycarbonyl radical and RuCl₃ as catalyst, affording a series of biologically valuable 4-[(methoxycarbonyl)methyl]-3,4-dihydroisoquinolinones with good tolerance and insensitivity to moisture in one pot under simple and mild conditions.

Catalytic enantioselective synthesis of fluoromethylated stereocenters by asymmetric hydrogenation

Fluoromethyl groups possess specific steric and electronic properties and serve as a bioisostere of alcohol, thiol, nitro, and other functional groups, which are important in an assortment of molecular recognition processes. Herein we report a catalytic method for the asymmetric synthesis of a variety of enantioenriched products bearing fluoromethylated stereocenters with excellent yields and enantioselectivities. Various N,P-ligands were designed and applied in the hydrogenation of fluoromethylated olefins and vinyl fluorides.

Herein, a catalytic asymmetric hydrogenation to synthesize various products bearing fluoromethylated stereocenters has been developed.

Hydrogenation of fluorinated molecules: an overview

The review aims at providing an overview on the developments made in hydrogenation reactions of molecules having various fluorinated groups (F, CF3, CF2H, CF2Rf). Indeed, the hydrogenation of fluorine-containing molecules is a straightforward and atom-economical way to access challenging (chiral) fluorinated scaffolds. This promising field is still in its infancy and milestones are expected in the coming years. To illustrate that, the review will highlight the major contributions made in that field and will be organized by fluorinated groups.