Thiazolyl-phosphine hydrochloride salts: effective auxiliary ligands for ruthenium-catalyzed nitrile hydration reactions and related amide bond forming processes in water

Metal-catalyzed nitrile hydration reactions: The specific contribution of ruthenium

“…On the other hand, the utility of complex 26 in promoting the formation of primary amides in water by catalytic rearrangement of aldoximes and direct coupling of aldehydes with hydroxylamine was also demonstrated [39]. and 25-26, the requirement of rather elaborated phosphine ligands makes them unappealing face to practical applications.…”

Exploring Rhodium(I) Complexes [RhCl(COD)(PR3)] (COD = 1,5-Cyclooctadiene) as Catalysts for Nitrile Hydration Reactions in Water: The Aminophosphines Make the Difference

“…Given their greater substrate scope and easier handling, methods based on homogeneous or heterogeneous metal-catalysts -3 -represent more attractive and powerful alternatives. 5 In this context, remarkable results have been obtained in recent years using homogeneous ruthenium catalysts containing as auxiliary ligands pyridyl-phosphines, 6 aminoaryl-phosphines, 7 thiazolyl-phosphines, 8 1,3,5-triaza-7-phosphaadamantane (PTA) and related cage-like aminophosphines, 9 tris(dimethylamino)phosphine 10 or phosphinites (R 2 POH). 11,12 The excellent activities were in most cases attributed to the activating effect that the heteroatoms present in the structures of these P-donor ligands exert on the water molecules by H-bonding or deprotonation.…”

Ruthenium-Catalyzed Amide-Bond Formation

“…the NH 2 OH·HCl salt associated with NaHCO 3 , commercially available hydroxylamine solution (50 wt% in H 2 O) could also be employed, improving notably the atom economy of the overall process since only water was generated as byproduct. More recently, the highly watersoluble complex 9 (Figure 3), which contains a thiazolyl-phosphine hydrochloride salt as ligand, was also found active in the synthesis of primary amides from aldoximes and aldehydes using water as solvent [45]. On the other hand, the preparation of secondary amides from aldoximes has been recently achieved through the one-pot sequential rearrangement/N-alkylation process depicted in Scheme 18 [93].…”

“…It is also worthy of note that, after selective crystallization of the final amides, recycling of the aqueous phase containing complexes 4 (2 times) [40] and 5 (6 times) [42] was possible. The arene-ruthenium(II) complex 9, bearing the water-soluble and potentially H-bond acceptor ligand tris(5-(2-aminothiazolyl))-phosphine trihydrochloride (Figure 3), featured also a high activity (TOF up to 66 h -1 ), productivity (TON up to 9800), substrate scope and functional group tolerance, combined with an effective recycling (up to five consecutive runs) [45]. Selective conversion of nitriles to amides, in water under neutral conditions, was also described employing complexes [RuCl 2 ( 6 -arene){P(NMe 2 ) 3 }] (arene = C 6 H 6 , p-cymene, 1,3,5-C 6 H 3 Me 3 , C 6 Me 6 ) as catalysts.…”