Sequential Ruthenium Catalysis for Olefin Isomerization and Oxidation: Application to the Synthesis of Unusual Amino Acids

Abstract

How can you use a ruthenium isomerization catalyst twice? A ruthenium-catalyzed sequence for the formal two-carbon scission of allyl groups to carboxylic acids has been developed. The reaction includes an initial isomerization step using commercially available ruthenium catalysts followed by in situ transformation of the complex to a metal-oxo species, which is capable of catalyzing subsequent oxidation reactions. The method enables enantioselective syntheses of challenging α-tri- and tetrasubstituted α-amino acids including an expedient total synthesis of the antiepileptic drug levetiracetam.

Chemistry of Bridged Lactams: Recent Developments

“…In 2017, Stoltz and co-workers reported the synthesis of a bridged hydantoin by asymmetric α-allylation, Ru-catalyzed olefin isomerization, oxidative cleavage, Curtius rearrangement and N -cyclization onto the isocyanate (Figure 12) [30]. The cyclization is performed by the same mechanism as reported previously by Brouillette [31]; however, the method avoids the use of toxic lead acetate.…”

Transition metal-catalyzed alkene isomerization as an enabling technology in tandem, sequential and domino processes

“…6). 26 Their strategy relies on the formation of thermodynamically more stable internal olefins followed by oxidative cleavage of the repositioned unsaturation. Using Nishida's protocol (vide infra), the initial Ru-alkylidene complex Ru2 is converted in situ into a [Ru-H] isomerization catalyst Ru3.…”

“…By exploiting the propensity of enol ethers to undergo intramolecular rearrangements when brought in close proximity of another reactive unsaturation, Tanaka and co-workers identified a cationic bisphosphine-rhodium complex ([(ddpf)Rh(cod)]BF 4 ) for the isomerization/propargyl Claisen rearrangement of allyl propargyl ethers (26) to allenes (27) (Fig. 11).…”

Metal Organic Frameworks as Heterogeneous Catalysts in Olefin Epoxidation and Carbon Dioxide Cycloaddition

“…C=C bond epoxidation is an attractive reaction for industrial process to obtain raw materials for epoxy resin, polymers, and pharmaceutical intermediates. Although homogenous catalysts in the epoxidation of alkene have been largely studied in the past few decades, the separation from the reaction mixture and its subsequent reusability remain open challenges [26,27]. CO 2 is the primary greenhouse gas in the atmosphere, and it is the cause of environmental and energy-related problems in the world.…”

“…C=C bond epoxidation is an attractive reaction for industrial process to obtain raw materials for epoxy resin, polymers, and pharmaceutical intermediates. Although homogenous catalysts in the epoxidation of alkene have been largely studied in the past few decades, the separation from the reaction mixture and its subsequent reusability remain open challenges [26,27]. A significant number of MOFs has been recently reported to catalyse the CO 2 cycloaddition reaction to epoxides to give cyclic organic carbonates (OCs) and several papers describe the potential and effectiveness of MOFs in this important process, so it is necessary to identify better strategies to build new advanced materials as MOFs or MOF-based species to grow selectivity, capacity, and conversion of this catalytic reaction.…”