Chiral Allene-Containing Phosphines in Asymmetric Catalysis

Abstract

Traditionally, ligands used in asymmetric catalysis have contained either stereogenic atoms or hindered single bonds (atropisomerism), or both. Here we demonstrate that allenes, chiral 1,2-dienes, appended with basic functionality can serve as ligands for transition metals. We describe an allene-containing bisphosphine that, when coordinated to Rh(I), promotes the asymmetric addition of aryl boronic acids to α-keto esters with high enantioselectivity. Solution and solid-state structural analysis reveals that one olefin of the allene can coordinate to transition metals generating bi- and tri-dentate ligands.

Organophosphines in organoplatinum complexes – Structural aspects of trans -PtP 2 CCl derivatives

“…[108] one metallocyclic ring is five-(PC 2 C) and the other one is six-(PC 3 C) membered with the values of 83.6 and 89.5 , respectively. In remaining two complexes the ligands form a pair of six-membered metallocyclic rings with the mean PePteC bite angles of 88.5 (PC 3 S) [109] and 88.6 (PNC 2 C) [110]. The mean Pt-L bond distance elongated in the order: 2.02 Å (C, trans to Cl) < 2.275 Å (P, trans to P) < 2.380 Å (Cl).…”

Synthesis of Allenes Bearing Phosphine Oxide Groups and Investigation of Their Reactivity toward Gold Complexes

“…[4] The same group then furthera dapted the parent structure II to append phosphineg roups bearing CF 3 electronwithdrawing groups in place of the phosphineo xide ones.T he resulting ligand could coordinate to Rh(I), featuring coordination to the allene moiety, and provide complex III,w hich proved to be ah ighly efficient catalyst for the enantioselective arylation of aketo esters( Scheme 1). [5] Because of our long-standing interest in gold catalysis, [6] we wishedt oi nvestigate the reactivity of new allene scaffolds bearing phosphineoxide groups as coordinating units.C oordination of gold(I) to allenes has indeed been theoretically studied in ordert or ationalize some reaction pathways. [7] In addition,s ome coordination complexes have also been isolated and characterized by X-ray crystallography.…”

Silver‐Catalyzed Allenylation and Enantioselective Propargylation Reactions of Ketones

“…[19][20][21] In 2006, the Leighton group reported the highly enantioselective allylation of prochiral 2'-hydroxyphenylketones, where the phenol directing group accelerates reaction rates and differentiates the arenes. We were intrigued by the challenge presented by prochiral diaryl ketones, as few methods for the asymmetric addition to this class of ketones exist.…”