Iridium-Catalyzed Asymmetric Allylic Amination Reactions with N-Aryl Phosphoramidite Ligands

Molybdenum-Catalyzed Regio- and Enantioselective Amination of Allylic Carbonates: Total Synthesis of (S)-Clopidogrel

The first molybdenum-catalyzed highly regio- and enantioselective allylic amination of both aryl- and alkyl-substituted branched allylic carbonates has been developed. A wide variety of amines, including drugs and complex bioactive molecules, underwent successful amination with excellent reaction outcomes (up to 96% yield, >99% ee, and >20:1 b/l). The reaction could be scaled up and has been applied to the total synthesis of chiral drug molecule (S)-clopidogrel (Plavix).

Iridium-Catalyzed Intramolecular Asymmetric Allylic Etherification of Pyrimidinemethanols: Enantioselective Construction of Multifunctionalized Pyrimidine-Fused Oxazepines

An iridium-catalyzed intramolecular asymmetric allylic etherification of pyrimidinemethanols is described. In the presence of chiral-bridged biphenyl phosphoramidite ligand L3 and triethylborane, this process provided a class of novel pyrimidine-fused oxazepanes in up to 99% yield with 99.5% enantiomeric excess. The work addresses the challenge of insufficient nucleophilicity of aliphatic alcohols for allyl substitution and indicates the vital value of chiral-bridged biphenyl phosphoramidites. Various multifunctionalized transformations of the products further demonstrate the robust synthetic utility of this methodology.

Iridium-catalyzed intramolecular asymmetric allylic etherification of salicylic acid derivatives with chiral-bridged biphenyl phosphoramidite ligands

Iridium-catalyzed intramolecular asymmetric allylic etherification of salicylic acid derivatives was successfully realized for the first time.

Catalytic asymmetric synthesis of quaternary trifluoromethyl α- to ε-amino acid derivatives via umpolung allylation/2-aza-Cope rearrangement

In this study, we developed an efficient Ir-catalyzed cascade umpolung allylation/2-aza-Cope rearrangement of tertiary α-trifluoromethyl α-amino acid derivatives for the preparation of a variety of quaternary α-trifluoromethyl α-amino acids in high yields with excellent enantioselectivities. The umpolung reactivity empowered by the activation of the key isatin-ketoimine moiety obviates the intractable enantioselectivity control in Pd-catalyzed asymmetric linear α-allylation. In combination with quasi parallel kinetic resolution or kinetic resolution, the generality of this method is further demonstrated by the first preparation of enantioenriched quaternary trifluoromethyl β-, γ-, δ- and ε-amino acid derivatives.

Regio- and Enantioselective Iridium-Catalyzed N-Allylation of Indoles and Related Azoles with Racemic Branched Alkyl-Substituted Allylic Acetates

Cyclometallated π-allyliridium C,O-benzoates modified with (S)-tol-BINAP, which are stable to air, water, and SiO₂ , catalyze highly enantioselective N-allylations of indoles and related azoles. This reaction complements previously reported metal-catalyzed indole allylations in that complete levels of N versus C3 and branched versus linear regioselectivity are observed.

Enantioselective Syntheses of Tricyclic Benzimidazoles via Intramolecular Allylic Aminations with Chiral-Bridged Biphenyl Phosphoramidite Ligands

The first iridium-catalyzed enantioselective intramolecular allylic aminations of benzimidazole-tethered allylic carbonates were developed, providing three classes of tricyclic benzimidazoles bearing a tertiary carbon stereogenic center in high yields and excellent enantioselectivities (up to 99% yield, 99% ee). Wide substrate scope, excellent catalytic efficiency and mild conditions rendered this protocol particularly superior and practical. Impressively, the chiral bridge with a tunable structure was shown to provide a very good adjustment space for the chiral environment. The excellent catalytic performance of the ligands manifested their advantages over the bisphenol-based and BINOL-derived counterparts in these transformations. It also highlighted the potential application value of the chiral-bridged ligands.

Iridium-Catalyzed Asymmetric Allylic Substitution Reactions

In this review, we summarize the origin and advancements of iridium-catalyzed asymmetric allylic substitution reactions during the past two decades. Since the first report in 1997, Ir-catalyzed asymmetric allylic substitution reactions have attracted intense attention due to their exceptionally high regio- and enantioselectivities. Ir-catalyzed asymmetric allylic substitution reactions have been significantly developed in recent years in many respects, including ligand development, mechanistic understanding, substrate scope, and application in the synthesis of complex functional molecules. In this review, an explicit outline of ligands, mechanism, scope of nucleophiles, and applications is presented.

Regio- and Enantioselective Iridium-Catalyzed Amination of Racemic Branched Alkyl-Substituted Allylic Acetates with Primary and Secondary Aromatic and Heteroaromatic Amines

The air- and water-stable π-allyliridium C,O-benzoate modified by ( S)-tol-BINAP, ( S)-Ir-II, catalyzes highly regio- and enantioselective Tsuji-Trost-type aminations of racemic branched alkyl-substituted allylic acetates using primary or secondary (hetero)aromatic amines. Specifically, in the presence of ( S)-Ir-II (5 mol%) in DME solvent at 60-70 °C, α-methyl allyl acetate 1a (100 mol%) reacts with primary (hetero)aromatic amines 2a-2l (200 mol%) or secondary (hetero)aromatic amines 3a-3l (200 mol%) to form the branched products of allylic amination 4a-4l and 5a-5l, respectively, as single regioisomers in good to excellent yield with uniformly high levels of enantioselectivity. As illustrated by the conversion of heteroaromatic amine 3m to adducts 6a-6g, excellent levels of regio- and enantioselectivity are retained across diverse branched allylic acetates bearing normal alkyl or secondary alkyl substituents. For reactants 3n-3p, which incorporate both primary and secondary aryl amine moieties, regio- and enantioselective amination occurs with complete site-selectivity to furnish adducts 7a-7c. Mechanistic studies involving amination of the enantiomerically enriched, deuterium-labeled acetate 1h corroborate C-N bond formation via outer-sphere addition.

Rhodium-catalyzed asymmetric hydroboration of γ,δ-unsaturated amide derivatives: δ-borylated amides

γ,δ-Unsaturated amides in which the alkene moiety bears an aryl or heteroaryl substituent undergo regioselective rhodium-catalyzed δ-borylation by pinacolborane to afford chiral secondary benzylic boronic esters. The results contrast the γ-borylation of γ,δ-unsaturated amides in which the disubstituted alkene moiety bears only alkyl substituents; the reversal in regiochemistry is coupled with a reversal in the sense of π-facial selectivity.

Amphiphilic π-Allyliridium C,O-Benzoates Enable Regio- and Enantioselective Amination of Branched Allylic Acetates Bearing Linear Alkyl Groups

The first examples of amphiphilic reactivity in the context of enantioselective catalysis are described. Commercially available π-allyliridium C,O-benzoates, which are stable to air, water and SiO2 chromatography, and are well-known to catalyze allyl acetate-mediated carbonyl allylation, are now shown to catalyze highly chemo-, regio- and enantioselective substitutions of branched allylic acetates bearing linear alkyl groups with primary amines.

Total synthesis of natural productsviairidium catalysis

An overview of the highlights in total synthesis of natural products using iridium as a catalyst is given.

Iridium-Catalyzed Stereoselective Allylic Alkylation Reactions with Crotyl Chloride

The development of the first enantio-, diastereo-, and regioselective iridium-catalyzed allylic alkylation reaction of prochiral enolates to form an all-carbon quaternary stereogenic center with an aliphatic-substituted allylic electrophile is disclosed. The reaction proceeds with good to excellent selectivity with a range of substituted tetralone-derived nucleophiles furnishing products bearing a newly formed vicinal tertiary and all-carbon quaternary stereodyad. The utility of this protocol is further demonstrated via a number of synthetically diverse product transformations.