Contemporaneous Dual Catalysis: Chemoselective Cross-Coupling of Catalytic Vanadium–Allenoate and π-Allylpalladium Intermediates

Abstract

This paper presents a detailed investigation of a dual catalytic system that combines a vanadium-catalyzed Meyer-Schuster rearrangement and a palladium-catalyzed allylic alkylation. The implementation of this novel reaction relies on matching the formation rates of vanadium-allenoate and π-allylpalladium intermediates with their bimolecular coupling rate in order to minimize the undesired protonation or O-alkylation of the catalytically generated intermediates. Chemoselectivity in this dual catalytic process was successfully achieved by adjusting ligand structure and catalyst loading ratios of the vanadium and palladium catalysts. A great range of coupling partners for both the propargyl alcohol and allyl carbonate components are readily accommodated in this new transformation, which in turn provides a novel avenue to a variety of α-allylated α,β-unsaturated ketones, esters, and amides in moderate to excellent isolated yields.

Synergistic catalysis: A powerful synthetic strategy for new reaction development

“…In 2011, however, Trost and Luan developed a unique synergistic approach to the synthesis of α-allyl-α,β-unsaturated ketones. 12 In previous studies, it was demonstrated that oxyvanadium catalysts 21 induces a 1,3-transposition of propargylic alcohols via nucleophilic vanadium-allenoate complex 22 (Eq 1). 13 The authors hypothesized that this catalytic nucleophile should also participate in a Tsuji-Trost allylation and couple with electrophilic π-allyl palladium complexes, forming α-allyl-α,β-unsaturated ketones.…”

“…Synergistic catalysis also has the potential to couple many types of irreversibly-formed, fleeting intermediates, as exemplified with Trost and Luan’s palladium-and vanadium-catalyzed synthesis of α-allylated-α,β-unsaturated ketones (Section 2.1, Scheme 8). 12 Both reactive intermediates are formed irreversibly, but still find each other and react to form the desired product before either engage in side reactions. As the concept of synergistic catalysis expands, the number of new and novel transformations this strategy provides will continue to grow.…”

Bimetallic catalysis for C–C and C–X coupling reactions

“… 61 As they found that this aromatic activation was essential for the initial vanadium-catalysed rearrangement, later than year they expanded the scope to include aliphatic propargylic alcohols with an activating alkoxy group on the alkyne fragment. 62 …”

On the Importance of Considering Multinuclear Metal Sites in Homogeneous Catalysis Modeling

“…Another example concerns the Pd-catalyzed Tsuji-Trost allylic substitutions and its combination with the V-catalyzed Meyer-Schuster rearrangement (Scheme 3) [21,22]. This coupling between propargylic alcohols and allylic carbonates promoted cooperatively by palladium and vanadium Fig.…”