C₁‐Symmetric Monosubstituted Chiral Diene Ligands in Asymmetric Rhodium‐Catalyzed 1,4‐Addition Reactions

Abstract

Asymmetric catalysis provides outstanding tools to introduce chiral information to a substrate by using only catalytic amounts of a chiral transition-metal complex.[1] The success of these efficient asymmetric processes relies on the development of chiral ligands that form a complex with the metal; until very recently phosphorus-, nitrogen-, and oxygen-containing chiral ligands were the only ones available. Recently, the groups of Hayashi and Carreira independently reported the use of chiral dienes in asymmetric catalysis: [2] high levels of enantioselectivity were achieved in both the iridiumcatalyzed kinetic resolution of allyl carbonates [3] and the rhodium-catalyzed 1,4-additions of organoboron reagents to Michael acceptors. [4,5]

Rhodium‐ and Palladium‐Catalyzed Asymmetric Conjugate Additions

“…Since the first application of chiral (S,S)-2,5-dibenzylbicyclo[2.2.1]heptadiene ((S,S)-L27b) in the addition of phenylboronic acid to cyclohex-2-enone by Hayashi and coworkers [93], a variety of bicyclic diene scaffolds [94][95][96][97][98][99][100][101][102][103][104] has been successfully applied (Scheme 1.15). Independently, Carriera and coworkers reported the application of a chiral diene for Ir-catalyzed allylic substitution [105].…”

“…A systematic exploration of different bicyclic scaffolds for chiral diene, revealed that the 2,5-disubstituted bicyclo [ onto β-silyl α,β-unsaturated ketones [104]. Using the scaffold developed by Carreria (L30), it was found that just the mono-substitution of the bicyclo[2.2.2]octadiene framework with an aryl moiety (L29) was necessary to achieve high enantioselectivities [44,103]. In this first systematic investigation of the steric effects of mono-substituted chiral dienes, the ortho positions on the aromatic moiety (i.e., 2,6-Me 2 C 6 H 3 ) were found to be important to achieve highest selectivities.…”

Synthesis and Suzuki–Miyaura Cross‐Coupling of Enantioenriched Secondary Potassium β‐Trifluoroboratoamides: Catalytic, Asymmetric Conjugate Addition of Bisboronic Acid and Tetrakis(dimethylamino)diboron to α,β‐Unsaturated Carbonyl Compounds

“…[26] Perhaps the most common method for the generation of β -arylated amides is a transition metal-catalyzed conjugate addition of an arylmetallic species to an α , β -unsaturated amide (route b). [27] A rhodium-catalyzed addition of arylboronic acids to lactams provides the desired β -arylated products in yields and enantiomeric excess up to 99%. [27b] However, the rhodium-catalyzed addition of phenylboronic acid to an acyclic amide provided the desired product in only 40% yield with an enantiomeric ratio of 90:10.…”

Rh-catalyzed asymmetric 1,4-addition reactions to α,β-unsaturated carbonyl and related compounds: an update

“…128,129 However, the applications of bis-sulfoxide ligands in stereoselective synthesis have been largely overlooked. [130][131][132][133][134][135][136][137] In 2008, Dorta et al have disclosed that chiral bis-sulfoxides can be employed as ligands in stereoselective late-transition metal catalysis. Pre-catalyst [{(P,R,R)-p-tol-BINASO}RhCl] 2 L24 acts as a reactive showing excellent stereoselectivities in the 1,4-addition of different arylboronic acids 2 to cyclic, electron-poor compounds 1a-c,g,w.…”