Gold‐Catalyzed Intermolecular Anti‐Markovnikov Hydroamination of Alkylidenecyclopropanes

The cationic gold phosphine complex [{PCy₂(o‐biphenyl)}Au(NCMe)]⁺SbF₆^? (Cy=cyclohexyl) catalyzes the intermolecular, anti‐Markovnikov hydroamination reaction of monosubstituted and cis‐ and trans‐disubstituted alkylidenecyclopropanes (ACPs) with imidazolidin‐2‐ones and other nucleophiles. This reaction forms 1‐cyclopropyl alkylamine derivatives in high yield and with high regio‐ and diastereoselectivity. NMR spectroscopic analysis of gold π‐ACP complexes and control experiments point to the sp hybridization of the ACP internal alkene carbon atom as controlling the regiochemistry of the ACP hydroamination reaction.     

Stoichiometric and Catalytic Inter‐ and Intramolecular Hydroamination of Terminal Alkynes by Frustrated Lewis Pairs

Frustrated Lewis pairs (FLPs) based on sterically encumbered anilines and the Lewis acid B(C₆F₅)₃ were found to react with terminal alkynes effecting intermolecular hydroamination affording iminium alkynylborate species of the form [RPhN?C(R′)Me][R′CCB(C₆F₅)₃]. In these cases, the reagent ratio of borane, aniline, and alkyne is 1:1:2. These reactions could also be performed in an intramolecular fashion by using anilines with alkynyl substituents effecting cyclization reactions. The use of 10 mol % B(C₆F₅)₃ under a H₂ atmosphere provides a one‐pot synthesis of the pyrrolidine 12 , the piperidines 13 – 15 , the azepane 16 , the isoindoline 17 , and the benzoxazine 18 .     

Asymmetric hydroamination of aminoallenes catalyzed by titanium and tantalum complexes of chiral sulfonamide alcohol ligands

A series of bidentate sulfonamide alcohol ligands with varying steric and electronic properties was synthesized. The titanium and tantalum complexes of these ligands, prepared in situ from either Ti(NMe₂)₄ or Ta(NMe₂)₅, were used as catalysts for the asymmetric hydroamination of 6-methyl-hepta-4,5-dienylamine, giving exclusively the α-vinylpyrrolidine product. The titanium derived catalysts gave products with low stereoselectivity, up to 11%ee favoring (+)-2-(2-methyl-propenyl)-pyrrolidine, while the tantalum derived catalysts gave products with higher and opposite stereoselectivity, up to 34%ee favoring (−)-2-(2-methyl-propenyl)-pyrrolidine.     

Asymmetric brønsted Acid catalysis enabling hydroaminations of dienes and allenes

Acid treatment: Toste et?al. recently unveiled a new pathway for asymmetric Br?nsted acid catalysis of reactions involving dienes or allenes, and achieved highly efficient intramolecular hydroamination and hydroarylation reactions. The P?S bond proved necessary for reactivity, and dithiophosphoric acids emerged as efficient catalysts. The association/displacement sequence led to chiral pyrrolidines and isoxazolidines in excellent yields and ee?values.     

Catalytic Organometallic Reactions of Ammonia

Until recently, ammonia had rarely succumbed to catalytic transformations with homogeneous catalysts, and the development of such reactions that are selective for the formation of single products under mild conditions has encountered numerous challenges. However, recently developed catalysts have allowed several classes of reactions to create products with nitrogen‐containing functional groups from ammonia. These reactions include hydroaminomethylation, reductive amination, alkylation, allylic substitution, hydroamination, and cross‐coupling. This Minireview describes examples of these processes and the factors that control catalyst activity and selectivity.     

Gold(I)/Chiral Brønsted Acid Catalyzed Enantioselective Hydroamination–Hydroarylation of Alkynes: The Effect of a Remote Hydroxyl Group on the Reactivity and Enantioselectivity

The catalytic enantioselective hydroamination–hydroarylation of alkynes under the catalysis of (R₃P)AuMe/(S)‐3,3′‐bis(2,4,6‐triisopropylphenyl)‐1,1′‐binaphthyl‐2,2′‐diyl hydrogenphosphate ((S)‐TRIP) is reported. The alkyne was reacted with a range of pyrrole‐based aromatic amines to give pyrrole‐embedded aza‐heterocyclic scaffolds bearing a quaternary carbon center. The presence of a hydroxyl group in the alkyne tether turned out to be very crucial for obtaining products in high yields and enantioselectivities. The mechanism of enantioinduction was established by carefully performing experimental and computational studies.     

Amine‐bis(phenolate) Iron(III)‐Catalyzed Formal Hydroamination of Olefins

A practical synthesis of highly functionalized amines by the formal hydroamination reaction of alkenes with nitroarenes catalyzed by an air stable amine‐bis(phenolate) iron(III) complex is reported. The reaction uses an easily handled silane, low catalyst loadings, and mild reaction conditions. A wide range of substrates are transformed with synthetically useful yields (21 examples).