Phosphine‐ and Hydrogen‐Free: Highly Regioselective Ruthenium‐Catalyzed Hydroaminomethylation of Olefins

A highly regioselective ruthenium‐catalyzed hydroaminomethylation of olefins is reported. Using easily available trirutheniumdodecacarbonyl an efficient sequence consisting of a water‐gas shift reaction, hydroformylation of olefins, with subsequent imine or enamine formation and final reduction is realized. This novel procedure is highly practical (ligand‐free, one pot) and economic (low catalyst loading and inexpensive metal). Bulk industrial as well as functionalized olefins react with various amines to give the corresponding tertiary amines generally in high yields (up to 92 %), excellent regioselectivities (n/iso>99:1), and full chemoselectivity in favor of terminal olefins.     

Hydroaminomethylation Beyond Carbonylation: Allene–Imine Reductive Coupling by Ruthenium‐Catalyzed Transfer Hydrogenation

Ruthenium(II)‐catalyzed hydrogen transfer from 2‐propanol mediates reductive coupling of 1,1‐disubstituted allenes with formaldimines with complete branch‐regioselectivity, thus representing a new method for hydroaminomethylation beyond classical hydroformylation/reductive amination.     

Amines made easily: a highly selective hydroaminomethylation of olefins

A highly chemo- and regioselective hydroaminomethylation of simple as well as functionalized alpha-olefins using a cationic rhodium precatalyst together with Xantphos as ligand is reported. Studies of the influence of ligands and reaction conditions led to an unprecedented selective hydroaminomethylation procedure. The novel procedure constitutes an economically attractive and environmentally favorable synthesis of secondary and tertiary aliphatic amines.     

A Multicatalytic Approach to the Hydroaminomethylation of α‐Olefins

We report an approach to conducting the hydroaminomethylation of diverse α‐olefins with a wide range of alkyl, aryl, and heteroarylamines at relatively low temperatures (70–80 °C) and pressures (1.0–3.4 bar) of synthesis gas. This approach is based on simultaneously using two distinct catalysts that are mutually compatible. The hydroformylation step is catalyzed by a rhodium diphosphine complex, and the reductive amination step, which is conducted as a transfer hydrogenation with aqueous, buffered sodium formate as the reducing agent, is catalyzed by a cyclometallated iridium complex. By adjusting the ratio of CO to H₂, we conducted the reaction at one atmosphere of gas with little change in yield. A diverse array of olefins and amines, including hetreroarylamines that do not react under more conventional conditions with a single catalyst, underwent hydroaminomethylation with this new system, and the pharmaceutical ibutilide was prepared in higher yield and under milder conditions than with a single catalyst.     

Glycerol Boosted Rh-Catalyzed Hydroaminomethylation Reaction: A Mechanistic Insight

We report a Rh-catalyzed hydroaminomethylation reaction of terminal alkenes in glycerol that proceeds efficiently under mild conditions to produce the corresponding amines in relatively high selectivity towards linear amines, moderate to excellent yields by using a low catalyst loading (1 mol % [Rh], 2 mol % phosphine) and relative low pressure (H₂/CO, 1:1, total pressure 10 bar). This work sheds light on the importance of glycerol in enabling enamine reduction via hydrogen transfer. Moreover, evidence for the crucial role of Rh as chemoselective catalyst in the condensation step has been obtained for the first time in the frame of the hydroaminomethylation reaction by precluding deleterious aldol condensation reactions. The hydroaminomethylation proceeds under a molecular regime; the outcome of catalytically active species into metal-based nanoparticles renders the catalytic system inactive.     

Synthesis of polyamines via hydroaminomethylation of alkenes with urea--a new, effective and versatile route to dendrons and dendritic core molecules

Polyamines, structurally related to putrescines and spermidines, are easily obtainable via hydroaminomethylation of methylallylphthalimide with primary or secondary amines. In addition, hydroaminomethylation of monoolefins with urea as a synthetic equivalent for ammonia, in contrast to other methods (e.g. the alkylation of ammonia or ammonium salts), allows selective synthesis of symmetric tertiary amines. By combining both methods dendrons and dendrimer cores are conveniently obtained.     

Regioselective hydroaminomethylation of 1,1-diaryl-allyl-alcohols: a new access to 4,4-diarylbutylamines

Pharmacologically active 4,4-diarylbutylamines like Fluspirilene and 4-amino-1,1-diarylbutan-1-ols like Difenidol were prepared in high yields via rhodium catalysed hydroaminomethylation of 1,1-diaryl-allylalcohols. Conversion of these olefins with carbon monoxide, hydrogen and secondary amines proceeds with complete regioselectivity. This group can easily be removed under acidic and hydrogenating conditions, enabling the transformation of 4-amino-1,1-diarylbutan-1-ols to 4,4-diarylbutylamines in high yields. Thus Fluspirilene was synthesised in 88% yield in four steps starting from commercially available materials.     

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.     

Transition‐metal‐catalyzed aminations and aziridinations of C?H and CC bonds with iminoiodinanes

Catalytic insertion or addition of a metal‐imido/nitrene species, generated from reaction of a transition‐metal catalyst with iminoiodanes, to C? H and C?C bonds offers a convenient and atom economical method for the synthesis of nitrogen‐containing compounds. Following this groundbreaking discovery during the second half of the last century, the field has received an immense amount of attention with a myriad of impressive metal‐mediated methods for the synthesis of amines and aziridines having been developed. This review will cover the significant progress made in improving the efficiency, versatility and stereocontrol of this important reaction. This will include the various iminoiodanes, their in situ formation, and metal catalysts that could be employed and new ligands, both chiral and non‐chiral, which have been designed, as well as the application of this functional group transformation to natural product synthesis and the preparation of bioactive compounds of current therapeutic interest. DOI 10.1002/tcr.201100018     

A highly efficient method for the hydroaminomethylation of long-chain alkenes under aqueous, biphasic conditions

The use of salts of secondary and primary amines with different inorganic and organic acids in hydroaminomethylation enables the quantitative conversion of 1-octene with high selectivity for saturated amines. We propose that a cationic rhodium species is formed under the acidic conditions which catalyses the hydrogenation of the enamine or imine formed subsequently. Thus the use of acids and amine salts enables the hydroaminomethylation of long-chain alkenes under aqueous, biphasic conditions with quantitative conversions and short reaction times.     

Enantioselective Iron‐Catalyzed Intramolecular Cyclopropanation Reactions

An iron‐catalyzed asymmetric intramolecular cyclopropanation was realized in high yields and excellent enantioselectivity (up to 97 % ee) by using the iron complexes of chiral spiro‐bisoxazoline ligands as catalysts. The superiority of iron catalysts exhibited in this reaction demonstrated the potential abilities of this sustainable metal in asymmetric carbenoid transformation reactions.     

General Olefin Synthesis by the Palladium‐Catalyzed Heck Reaction of Amides: Sterically Controlled Chemoselective NC Activation

Metal‐catalyzed reactions of amides proceeding via metal insertion into the N? CO bond are severely underdeveloped due to resonance stabilization of the amide bond. Herein we report the first Heck reaction of amides proceeding via highly chemoselective N? CO cleavage catalyzed by Pd⁰ utilizing amide bond ground‐state destabilization. Conceptually, this transformation provides access to a myriad of metal‐catalyzed transformations of amides via metal insertion/decarbonylation.     

General Olefin Synthesis by the Palladium‐Catalyzed Heck Reaction of Amides: Sterically Controlled Chemoselective N?C Activation

Metal‐catalyzed reactions of amides proceeding via metal insertion into the N CO bond are severely underdeveloped due to resonance stabilization of the amide bond. Herein we report the first Heck reaction of amides proceeding via highly chemoselective N CO cleavage catalyzed by Pd⁰ utilizing amide bond ground‐state destabilization. Conceptually, this transformation provides access to a myriad of metal‐catalyzed transformations of amides via metal insertion/decarbonylation.     

Highly regioselective hydroaminomethylation of terminal olefins to linear amines using Rh complexes with a Tetrabi phosphorus ligand

A highly regioselective hydroaminomethylation of terminal olefins catalyzed by Rh complexes with 2, 2′, 6, 6′‐tetrakis ((diphenylphosphino)methyl)‐1, 1′‐biphenyl (Tetrabi) ligand has been developed. Up to 99 % amine selectivity, 168 linear/branched amine product ratio (n/i), and 97.4 % linear amine yield has been obtained at a substrate/rhodium precursor ratio (S/Rh) of 1000 with this methodology. The turnover number was achieved 6930 at 10000 S/Rh ratio, and the n/i can reach up to >525. Several different olefins and secondary amines have been applied successfully with high chemoselectivity (99 %), yield (>98 %), and regioselectivity (>120).     

Complete Transmetalation in a Metal–Organic Framework by Metal Ion Metathesis in a Single Crystal for Selective Sensing of Phosphate Ions in Aqueous Media

A complete transmetalation has been achieved on a barium metal–organic framework (MOF), leading to the isolation of a new Tb‐MOF in a single‐crystal (SC) to single‐crystal (SC) fashion. It leads to the transformation of an anionic framework with cations in the pore to one that is neutral. The mechanistic studies proposed a core–shell metal exchange through dissociation of metal–ligand bonds. This Tb‐MOF exhibits enhanced photoluminescence and acts as a selective sensor for phosphate anion in aqueous medium. Thus, this work not only provides a method to functionalize a MOF that can have potential application in sensing but also elucidates the formation mechanism of the resulting MOF.     

An Amide‐Functionalized Dynamic Metal–Organic Framework Exhibiting Visual Colorimetric Anion Exchange and Selective Uptake of Benzene over Cyclohexane

A novel porous metal–organic framework (MOF) architecture is formed by a neutral amide‐functionalized ligand and copper(II). Upon desolvation, this compound undergoes a dynamic structural transformation from a one‐dimensional (1D) porous phase to a two‐dimensional (2D) non‐porous phase that shows selective uptake of benzene over cyclohexane. The as‐synthesized compound also acts as a visual colorimetric anion sensor for thiocyanate.     

Structural Transformation and Stabilization of Metal–Organic Motifs Induced by Halogen Doping

The structural transformation of supramolecular nanostructures with constitutional diversity and adaptability by dynamic coordination chemistry would be of fundamental importance for potential applications in molecular switching devices. The role of halogen doping in the formation of elementary metal–organic motifs on surfaces has not been reported. Now, the 9‐ethylguanine molecule (G) and Ni atom, as a model system, are used for the structural transformation and stabilization of metal–organic motifs induced by iodine doping on Au(111). The iodine atoms are homogeneously located at particular hydrogen‐rich locations enclosed by G molecules by electrostatic interactions, which would be the key for such an unexpected stabilizing effect. The generality and robustness of this approach are demonstrated in different metal–organic systems (G/Fe) and also by chlorine and bromine.     

Metal‐ and Oxidant‐Free Alkenyl C−H/Aromatic C−H Cross‐Coupling Using Electrochemically Generated Iodosulfonium Ions

A three‐step transformation consisting of 1) addition of electrochemically generated iodosulfonium ions to vinylarenes to give (1‐aryl‐2‐iodoethoxy)sulfonium ions, 2) nucleophilic substitution by subsequently added aromatic compounds to give 1,1‐diaryl‐2‐iodoethane, and 3) elimination of HI with a base to give 1,1‐diarylethenes was developed. The transformation serves as a powerful metal‐ and chemical‐oxidant‐free method for alkenyl C?H/aromatic C?H cross‐coupling.     

Oxygenation of Simple Olefins through Selective Allylic C−C Bond Cleavage: A Direct Approach to Cinnamyl Aldehydes

A novel metal‐free allylic C−C σ‐bond cleavage of simple olefins to give valuable cinnamyl aldehydes is reported. 1,2‐Aryl or alkyl migration through allylic C−C bond cleavage occurs in this transformation, which is assisted by an alkyl azide reagent. This method enables O‐atom incorporation into simple unfunctionalized olefins to construct cinnamyl aldehydes. The reaction features simple hydrocarbon substrates, metal‐free conditions, and high regio‐ and stereoselectivity.     

Triflic Acid‐Catalyzed Enynes Cyclization: A New Strategy beyond Electrophilic π‐Activation

The cyclization of enynes, catalyzed by a transition metal, represents a powerful tool to construct an array of cyclic compounds through electrophilic π‐activation. In this paper, we disclose a new and efficient strategy for enynes cyclization catalyzed by triflic acid. The salient features of this transformation includes a broad substrate scope, metal free synthesis, open flask and mild conditions, good yields, ease of operation, low catalyst loading, and easy scale‐up to gram scale. A preliminary mechanism study demonstrated that the activation model of the reaction was σ‐activation, which is different from the transition‐metal‐catalyzed enynes cyclization. Our strategy affords a complementary method to the traditional strategies, which use transition‐metal catalysts.