Catalytic conjunctive cross-coupling enabled by metal-induced metallate rearrangement

Abstract

Transition metal catalysis plays a central role in contemporary organic synthesis. Considering the tremendously broad array of transition-metal-catalyzed transformations, it is remarkable that the underlying elementary reaction steps are relatively few in number. Here we describe an alternative to the organometallic transmetallation step that is common in many metal-catalyzed reactions such as Suzuki-Miyaura coupling. Specifically, we demonstrate that vinyl boronic ester ate complexes, prepared by combining organoboronates and organolithium reagents, engage in Pd-induced metallate rearrangement wherein 1,2-migration of an alkyl or aryl group from boron to the vinyl α-carbon occurs concomitantly with C-Pd σ-bond formation. This elementary reaction enables a powerful cross-coupling reaction in which a chiral palladium catalyst merges three simple starting materials – an organolithium, an organoboronic ester, and an organotriflate – into chiral organoboronic esters with high enantioselectivity.

A general alkyl-alkyl cross-coupling enabled by redox-active esters and alkylzinc reagents

“…This convenient approach to diversely functionalized peptides provides a tool for the construction of therapeutic peptide leads, stapled peptides (28,29) and for applications in bioconjugation. (30)…”

Asymmetrische Synthese sekundärer und tertiärer Boronsäureester

“…[198] Morken nutzte eine elektrophile Arylpalladium(II)-Spezies zur Auslçsung der 1,2-Metallat-Verschiebung,w obei nicht-racemische,c hirale Liganden am Palladium die Tr ansformation insgesamt enantioselektiv machen (Schema 55). [198] Morken nutzte eine elektrophile Arylpalladium(II)-Spezies zur Auslçsung der 1,2-Metallat-Verschiebung,w obei nicht-racemische,c hirale Liganden am Palladium die Tr ansformation insgesamt enantioselektiv machen (Schema 55).…”

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

“…15 This reaction has been expanded to include the use of Grignard reagents and C(sp 2 ) halide electrophiles, 16 alkenyl migrating groups, 17 and has extended to nickel catalysts with both aryl 18 and alkyl electrophiles. 19 Perhaps unsurprisingly, direct extension to allyl electrophiles has proved a challenge, likely because η 3 coordination of the allyl group occupies a coordination site necessary for binding and activation of the ‘ate’ complex.…”