Pd-Catalyzed Conjunctive Cross-Coupling between Grignard-Derived Boron “Ate” Complexes and C(sp²) Halides or Triflates: NaOTf as a Grignard Activator and Halide Scavenger

Abstract

Catalytic enantioselective conjunctive cross-couplings that employ Grignard reagents are shown to furnish an array of non-racemic chiral organoboronic esters in an efficient and highly selective fashion. The utility of sodium triflate in facilitating this reaction is two-fold: it enables "ate" complex formation and overcomes catalytic inhibition by halide ions.

Palladium Catalyzed Asymmetric Three-Component Coupling of Boronic Esters, Indoles, and Allylic Acetates

“…13 Of more relevance to work described here, Morken and co-workers recently described an enantioselective coupling of vinyl boronic esters, alkyl/aryl lithium reagents and aryl triflates. 14 In this coupling, an ArPd(II) intermediate coordinates to the olefin moiety of a vinyl boronate species and thereby promotes facially selective 1,2-migration (Scheme 1c). …”

Intermolekulare Bildung zweier C‐C‐Bindungen an Olefinen mittels Bor‐basierter Staffelstrategien

“…Die Methode eignet sich ideal für Diarylierungen, Alkylarylierungen und Alkylvinylierungen von Olefinen, bei denen C(sp 2 )‐C(sp 3 )‐ oder C(sp 3 )‐C(sp 3 )‐Bindungen am Bor‐substituierten und C(sp 2 )‐C(sp 3 )‐Bindungen am benachbarten Kohlenstoffatom gebildet werden. Inzwischen wurde die Methode stark erweitert, und es wurde auch von Arylvinylierungen sowie Allylarylierungen berichtet.…”

Vinylidenation of Organoboronic Esters Enabled by a Pd‐Catalyzed Metallate Shift

“…With these modifications,3 -phenylpropyl (10)a nd n-octyl (11)m igrating groups were tolerated, as was asilyl ether (12). Ther eaction was also effective with cyclic substrates,including cyclopentyl (13), cyclohexyl (14), and N-Boc-protected piperidine (15) migrating groups.Migrating groups bearing potentially sensitive functional groups such as am onosubstituted olefin (16), amide (17), ester (18), or acetal (19)were also well-tolerated in this reaction. While examples in Table 2s uggest that the reaction is effective with Grignard-derived "ate" complexes, it should be noted that alkyllithium derived "ate" complexes often offer superior reactivity such that catalyst loading can be reduced to 1mol %Pd, with many substrates still achieving complete conversion in one hour (10)(11)(12).…”