Iridium-N,P-Ligand-Catalyzed Enantioselective Hydrogenation of Diphenylvinylphosphine Oxides and Vinylphosphonates

Abstract

Diphenylvinylphosphine oxides and di- and trisubstituted vinylphosphonates have been employed as substrates in iridium-catalyzed asymmetric hydrogenations. Complete conversions and excellent enantioselectivities (up to and above 99% ee) were observed for a range of substrates with both aromatic and aliphatic groups at the prochiral carbon. We have also hydrogenated electron-deficient carboxyethylvinylphosphonates with excellent stereoselectivity (up to and above 99% ee). The hydrogenated products of both classes of substrates are synthetically useful intermediates.

Development of iridium-catalyzed asymmetric hydrogenation: New catalysts, new substrate scope

“…30 3--d. Phosphonates Chiral phosphites are often produced by the resolution of racemic mixtures; 31 however iridium offers a reliable catalytic method to produce them with excellent stereoselectivities. 32 Chiral phosphites and phosphonic acid derivatives are primarily used by the pharmaceutical industry: as drugs for metabolic diseases or neurological disorders amongst others. 33 Also, the potential of phosphorus as a metal chelator allows these phosphites to be used in the field of carboxyalkylphosphonates as precursors.…”

Asymmetric Hydrogenation

“…Therefore, not only unfuctionalized alkenes but also alkenes with functional groups connected to their C=C double bonds have been hydrogenated with high to excellent enantioselectivity. Figure 6 shows examples of the [61], furan rings [62], -dehydroamino acid derivatives [63], ,β-unsaturated ketones [64],,β-unsaturated carboxylic acid esters [61], -alkoxy ,β-unsaturated acids [65], vinylphosphine oxides [66], enol phosphinates [67], vinyl boronates [68], and enamines [69,70]. Notably, substituted furans, vinyl boronates, and even enamines are hydrogenated with full conversion in high to excellent enantioselectivity.…”

Recent Advances in Iridium-Catalyzed Asymmetric Hydrogenation: New Catalysts, Substrates and Applications in Total Synthesis

“…[11] Besides P, Nligands, C,N-ligands having a coordinating N-heterocyclic carbene unit also gave promising results. [12] All these new ligands enhanced the substrate scope to various types of C=C bonds, allowing asymmetric hydrogenations of vinyl fluorides, [13] vinyl ethers, [14] enol phosphinates, [15] vinyl diphenylphosphine oxides, [16] vinyl boronates, [17] chromenes, [18] furanes, [19] indoles, [20] enamines, [21] protected and unprotected allylic alcohols, [22] and unsaturated carbonyl compounds. [22b,22c,23] …”