Development of Stereocontrolled Palladium(II)‐Catalyzed Domino Heck/Suzuki β,α‐Diarylation Reactions with Chelating Vinyl Ethers and Arylboronic Acids

Abstract

A stereoselective and 1,4-benzoquinone-mediated palladium(II)-catalyzed Heck/Suzuki domino reaction involving metal coordinating cyclic methylamino vinyl ethers and a number of electronically diverse arylboronic acids has been developed and studied. Diastereomeric ratios up to 39:1 and 78 % isolated yields were obtained. The stereoselectivity of the reaction was found to be highly dependent on the nature of the arylboronic acid and the amount of water present in the reaction mixture. Thus, a domino β,α-diarylation–reduction of chelating vinyl ethers can now be accomplished and stereochemically controlled, given that optimized conditions and an appropriate chiral auxiliary are used. To the best of our knowledge, this represents the first example of a stereoselective, oxidative Heck/Suzuki domino reaction in the literature.

Selective Palladium‐Catalyzed α,β‐Homodiarylation of Vinyl Esters in Aqueous Medium

“…Subsequent coordination of BQ and polar protic solvent molecule (water in particular) reconciles the assembled results. It would explain the considerable impact of the above compounds on the course of the reaction, and the proper concept of additional molecules coordination has already been proposed based on experimental outcomes [14b,c] and DFT calculations [25] . For a standard oxidative Heck coupling, the next catalytic step would be β‐elimination.…”

“…However, the main limitation here is the indispensable presence of the coordinating auxiliary with a strictly defined structure in the olefin molecule. When moieties dissimilar to 2‐(dimethylamino)ethyl (or its chiral analogs [14b] ) were used, the reaction yield dropped significantly or a poor mixture of various coupling products was obtained [14c] . Generally, for other electron‐rich olefins, the Heck coupling is rather not straightforward.…”

Ni-Catalyzed Enantioselective Reductive Diarylation of Activated Alkenes by Domino Cyclization/Cross-Coupling

“…Transition metal catalyzed alkene diarylation reactions involving simultaneous incorporation of two aryl groups across the double bond in a single operation have received substantial attention, allowing for the effective construction of complex and useful compounds with stereocenters from easily accessible starting materials . Oxidative diarylation of alkenes by installing two identical aryl groups using a sole organometallic reagent (ArM) as the aryl source is known . Alternatively, diarylation by the introduction of an aryl nucleophile (ArM) and an aryl electrophile (ArX) across alkenes has also been well studied. − However, reductive diarylation of alkenes by addition of two aryl electrophiles (ArX) without requiring the use of preprepared organometallic reagents remains unexploited (Scheme A). − …”

Palladium‐catalyzed difluoromethylation and difluoroalkylation reactions: An overview

“…When we consider the platinum group metals, palladium is comparatively cheaper. [ 27 ] Increased stereoselectivity, [ 28 ] regioselectivity, [ 29 ] and chemoselectivity [ 30 ] of many of the palladium‐catalyzed reactions could attract the attention of most of the researchers to use palladium as a catalyst in organic transformations. Alkylation, [ 31 ] cyclization, [ 32 ] oxidation, [ 33 ] cross‐coupling, [ 34,35 ] and a series of diverse reactions are catalyzed by palladium.…”