Allylamine Research Articles

Stereospecific 3‐Aza‐Cope Rearrangement Interrupted Asymmetric Allylic Substitution‐Isomerization

AbstractTransition‐metal catalyzed asymmetric allylic substitution with alkyl and heteroaryl carbon nucleophiles has been well‐established. However, the asymmetric allylic arylation of acyclic internal alkenes with aryl nucleophiles remains challenging and underdeveloped. Herein we report a stereospecific 3‐aza‐Cope rearrangement interrupted asymmetric allylic substitution‐isomerization (Int‐AASI) that enables asymmetric allylic arylation. By means of this stepwise strategy, both enantioenriched allylic arylation products and axially chiral alkenes could be readily obtained in high enantioselectivities. Experimental studies support a mechanism involving a cascade of asymmetric allylic amination, stereospecific 3‐aza‐Cope rearrangement and alkene isomerization. Density functional theory studies detailed the reasons of achieving the high chemoselectivity, regioselectivity, stereoselectivity and stereospecificity, respectively.

A Precise Route to Tetrasubstituted Allyl Amines via Regioselective Dicarbofunctionalization of Masked Propargyl Amines.

Allyl amines are vital components in various biologically important molecules and play a significant role in their function. Presently, most methods are geared toward the preparation of di- and trisubstituted allyl amines, leaving a gap for the development of more versatile approaches. We herein describe an approach to yield tetrasubstituted allyl amines through palladium (Pd)-catalyzed regioselective dicarbofunctionalization of masked N-phthalimide-protected propargyl amines. The cationic Pd-intermediate in conjunction with the masked amine exerts collective control for the reaction regioselectivity. This method accommodates a wide range of alkynes, aryl boronic acids, and aryl diazonium salts offering direct access to a wide range of unusual tetrasubstituted allyl amines.

Molybdenum Complex-Catalyzed N-Alkylation of Bulky Primary and Secondary Amines.

Aliphatic allylic amines are present in a large number of complex and pharmaceutically relevant molecules. The direct amination of allylic electrophiles serves as the most common method toward the preparation of these motifs. However, the use of feedstock reaction components (allyl alcohol and aliphatic amine) in these transformations remains a great challenge. Such a challenge primarily stems from the high Lewis basicity and large steric hindrance of aliphatic amines, in addition to the low reactivity of allylic alcohols. Herein, we report a general solution to these challenges. The developed protocol allows an efficient allylic amination of allyl alcohols with sterically bulky aliphatic amines in the presence of an inexpensive earth-abundant molybdenum complex. This simple and economic protocol also enables regioselective branched amination; the practicality of the reaction was shown in an efficient, scaled-up synthesis of several drugs.

Palladium-catalyzed allylic amination of vinyl bicyclo[1.1.0]butanes: a strain release approach toward alkylidenecyclobutanes

Palladium-catalyzed allylic amination of vinyl bicyclo[1.1.0]butanes: a strain release approach toward alkylidenecyclobutanes

Halide Perovskite Induces Halogen/Hydrogen Atom Transfer (XAT/HAT) for Allylic C−H Amination

AbstractAllylic C−H amination has emerged as a powerful tool to construct allylamines, common motifs in molecular therapeutics. Such reaction implies an oxidative path for C−H activation but furnishes reductive amines, inferring mild oxidants’ inactivity for C−H oxidation but strong oxidants’ detriment to products. Herein we report a heterogeneous catalytic approach that manipulates halogen‐vacancies of perovskite photocatalyst and exploits halogenated‐solvents (i.e. CH2Cl2, CH2Br2) as mild oxidants for selective C−H allyl amination with 19,376 turnovers. CsPbBr3 nanocrystals induce cooperative hydrogen‐atom‐transfer (HAT, C−H oxidation, and halogen‐vacancy CsPbBr3−x formation) and halogen‐atom‐transfer (XAT, CsPbBr3−x‐induced solvent reduction) under a radical chain mechanism. Terminal/internal olefins are amenable to forge aromatic/aliphatic, cyclic/acyclic, secondary/tertiary allylamines (70 examples), including drugs or their derivatives.

Physicochemical analysis on molecular interactions in binary liquid mixtures at various temperatures and correlation with the Jouyban–Acree model (3-pentanol with allyl amine, allyl alcohol, and allyl chloride)

ABSTRACT This study investigates the molecular interactions in binary mixtures of 3-pentanol with three allyl compounds (allyl amine, allyl alcohol, and allyl chloride) at various temperatures. The excess molar volume, excess isentropic compressibility, deviation in viscosity, and excess Gibbs free energy of activation of viscous flow were determined from measured values of densities, speeds of sound, and viscosities. The data were analysed to determine excess properties and deviations from ideal behaviour, highlighting the predominance of molecular interactions such as geometrical packing effects and free volume effects. The experimental results were correlated with the Jouyban−Acree model, which effectively relates the observed thermodynamic properties to the composition of the mixtures. This correlation allows for a deeper understanding of molecular interactions that influence the properties of these binary mixtures across different temperatures.

Stable Ditriflates of D‐Glucose in the Synthesis of Iminosugars and Polyhydroxylated Pipecolic Acids

AbstractA synthesis of the five membered iminosugar DAB and a divergent synthesis of the six membered iminosugar 1‐dehydromannojirimycin (DMJ) and the corresponding sugar imino acid are reported. They involve double nucleophilic displacements of a D‐xylose ditriflate by benzyl carbazate and a D‐glucose ditriflate by allyl amine, respectively. They are followed by a similar protocol consisting of hydrolysis and oxidation or reduction of the resulting bicyclic glycosides. This allowed DMJ to be obtained from the cheap sugar D‐glucose.

Development of Functionalized Polylactide Thin Films Using Poly(methylhydrogenosiloxane) Sol-Gel Process with Improved Antifouling Properties.

Biobased polylactide (PLA) films were modified with low reticulate polysiloxane gel acting as a scalable platform for the hydrophilization of polymeric film surface. The PLA thin film was first coated with poly(methylhydrogenosiloxane) (PMHS) by the sol-gel transition via the condensation of diethoxymethylsilane (DH) and triethoxysilane (TH) using trifluoromethanesulfonic acid as a catalyst. Then, hydrosilylation of Si-H bonds in the presence of Karstedt's catalyst allowed the covalent grafting of hydrophilic alkene-containing molecules, i.e., triethylene glycol monomethyl allyl (TEGMEA) and a new zwitterionic allylcarboxybetaine (ACB) synthesized for the first time by the quaternization of dimethyl allyl amine (DMAA) with β-propiolactone. PMHS coating on the PLA film was evidenced by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The observation by atomic force microscopy (AFM) revealed a homogeneous coating with low roughness (RMS = 0.29 nm). The hydrophilicity of functionalized PLA films was determined by water contact angle (WCA) measurements using the captive bubble method. A large increase in wettability properties was observed for both grafting with TEGMEA (WCA = 38°) and ACB (WCA = 42°) in comparison with the native PLA film (WCA = 80°). Moreover, the biocompatibility and antifouling efficiency of functionalized PLA films were evaluated by protein adsorption, bacterial adhesion, and cytotoxicity tests. The results indicate that the grafting of the two types of hydrophilic compounds does not affect the biocompatibility of PLA while significantly reducing protein adsorption and bacterial adhesion, thus showing the great potential of this surface functionalization strategy for applications in the medical field.

Stereospecific 3-Aza-Cope Rearrangement Interrupted Asymmetric Allylic Substitution-Isomerization.

Transition-metal catalyzed asymmetric allylic substitution with alkyl and heteroaryl carbon nucleophiles has been well-established. However, the asymmetric allylic arylation of acyclic internal alkenes with aryl nucleophiles remains challenging and underdeveloped. Herein we report a stereospecific 3-aza-Cope rearrangement interrupted asymmetric allylic substitution-isomerization (Int-AASI) that enables asymmetric allylic arylation. By means of this stepwise strategy, both enantioenriched allylic arylation products and axially chiral alkenes could be readily obtained in high enantioselectivities. Experimental studies support a mechanism involving a cascade of asymmetric allylic amination, stereospecific aryl 3-aza-Cope rearrangement and alkene isomerization. Density functional theory studies detailed the reasons of achieving the high chemoselectivity, regioselectivity, stereoselectivity and stereospecificity, respectively.

Asymmetric Amination of Unstrained C(sp3)-C(sp3) Bonds.

The asymmetric functionalization of unstrained C(sp3)-C(sp3) bonds could be a powerful strategy to stereoselectively reconstruct the backbone of an organic compound, but such reactions are rare. Although allylic substitutions have been used frequently to construct C-C bonds by the cleavage of more reactive C-X bonds (X is usually an O atom of an ester) by transition metals, the reverse process that involves the replacement of a C-C bond with a C-heteroatom bond is rare and generally considered thermodynamically unfavorable. We show that an unstrained, inert allylic C-C σ bond can be converted to a C-N bond stereoselectively via a designed solubility-control strategy, which makes the thermodynamically unfavorable process possible. The C-C bond amination occurs with a range of amine nucleophiles and cleaves multiple classes of alkyl C-C bonds in good yields with high enantioselectivity. A novel resolution strategy is also reported that transforms racemic allylic amines to the corresponding optically active allylic amine by the sequential conversion of a C-N bond to a C-C bond and back to a C-N bond. Mechanistic studies show that formation of the C-N bond is the rate-limiting step and is driven by the low solubility of the salt formed from the cleaved alkyl group in a nonpolar solvent.

Asymmetric Allylic Amination of Alkyl-Substituted Allylic Carbonates with Pyridones Catalyzed by the Krische Iridium Complex.

An efficient Ir-catalyzed asymmetric allylic amination reaction of alkyl-substituted allylic carbonates is disclosed. With the Krische iridium complex as the catalyst, asymmetric allylic amination of alkyl-substituted allylic carbonates with pyridones proceeds effectively, affording pyridone derivatives containing a stereocenter α to the nitrogen atom in excellent yields and enantioselectivity (up to 99% yield, 95% ee). This catalytic system broadens the substrate scope of the reaction compared with that of the known catalytic systems. This reaction can also be conducted on a gram scale, further enhancing its potential for synthetic application.

Enantioselective 1,2-Carboamination of 1,3-Dienes with N-Hydroxyphthalimide (NHP) Esters Enabled by a Photoinduced Pd Catalysis.

Herein, a photoinduced, Pd-catalyzed direct 1,2-carboamination of conjugated 1,3-dienes has been successfully achieved. Sequential regioselective C-C bond and enantioselective C-N bond formation allows rapid assembly of a wide range of value-added chiral allylic amines from readily available N-hydroxyphthalimide (NHP) esters and 1,3-dienes under mild conditions. This developed protocol further demonstrates the versatility and potency of the photoexcited Pd catalytic system with a bifunctional reagent in the streamlined difunctionalization of C═C bonds.

Palladium(0) and Brønsted Acid Co‐Catalyzed Enantioselective Hydro‐Cyclization of 2,4‐Dienyl Hydrazones and Oximes

AbstractThe transition metal‐catalyzed asymmetric hydro‐functionalization of 1,3‐dienes has been well explored, but most reactions focus on electron‐neutral substrates in an intermolecular manner. Here we first demonstrate that readily available 2,4‐dienyl hydrazones and oximes can be efficiently utilized in the hydro‐cyclization reaction under co‐catalysis of a Brønsted acid and a chiral palladium complex, furnishing multifunctional dihydropyrazones and dihydroisoxazoles, respectively. Diverse substitution patterns for both types of electron‐deficient diene compounds are tolerated, and corresponding heterocycles were generally constructed with moderate to excellent enantioselectivity, which can be elaborated to access products with higher molecular complexity and diversity. Control experiments and density functional theory calculations support that α‐regioselective protonation of dienyl substrates by acid and concurrent π‐Lewis base activation of Pd0 complex is energetically favoured in the formation of active π‐allylpalladium intermediates, and an outer‐sphere allylic amination or etherification mode is adopted to deliver the observed cyclized products enantioselectively.

Photoinduced Electron Donor Acceptor Complex-Enabled α-C(sp3)-H Alkenylation of Amines.

Allylic amines are prevalent and vital structural components present in many bioactive compounds and natural products. Additionally, they serve as valuable intermediates and building blocks, with wide-ranging applications in organic synthesis. However, direct α-C(sp3)-H alkenylation of feedstock amines, particularly for the preparation of α-alkenylated cyclic amines, has posed a longstanding challenge. Herein, we present a general, mild, operationally simple, and transition-metal-free α-alkenylation of various readily available amines with alkenylborate esters in excellent E/Z - and diastereoselectivities. This method features good compatibility with water and oxygen, broad substrate scope, and excellent functional group tolerance, thereby enabling the late-stage modification of various complex molecules. Mechanistic studies suggest that the formation of a photoactive electron donor-acceptor complex between 2-iodobenzamide and the tetraalkoxyborate anion, which subsequently undergoes photoinduced single electron transfer and intramolecular 1,5-hydrogen atom transfer to generate the crucial α-amino radicals, is the key to success of this chemistry.

Integrated Approach for Allyl Amine Synthesis Combining the Decarboxylative Coupling of Arylacrylic Acids with the Petasis Reaction.

A metal-free multicomponent reaction strategy for synthesizing allyl amines through decarboxylative coupling combined with the Petasis reaction is described. Utilizing (E)-3-(2,4,6-trimethoxyphenyl)acrylic acid, various boronic acids, a formaldehyde solution, and primary amines, the method operates efficiently without metal catalysts. Investigations reveal that electron-donating substituents in cinnamic acid derivatives significantly enhance reactivity, which is crucial for effective transformations. Under the optimized conditions, yields of ≤78% were obtained across a diverse range of 30 allyl amines.

Surface Chemistry Induced IgG Unfolding and Modulation of Immune Responses.

Immunoglobulin G (IgG) comprises a significant portion of the protein corona that forms on biomaterial surfaces and holds a pivotal role in modulating host immune responses. To shed light on the important relationship between biomaterial surface functionality, IgG adsorption, and innate immune responses, we prepared, using plasma deposition, four surface coatings with specific chemistries, wettability, and charge. We found that nitrogen-containing coatings such as these deposited from allylamine (AM) and 2-methyl-2-oxazoline (POX) cause the greatest IgG unfolding, while hydrophilic acrylic acid (AC) surfaces allowed for the retention of the protein structure. Structural changes in IgG significantly modulated macrophage attachment, migration, polarization, and the expression of pro- and anti-inflammatory cytokines. Unfolded IgG on the POX and AM surfaces enhanced macrophage attachment, migration, extracellular trap release, and pro-inflammatory factors production such as IL-6 and TNF-α. Retention of IgG structure on the AC surface downregulated inflammatory responses. The findings of this study demonstrate that the retention of protein structure is an essential factor that must be taken into consideration when designing biomaterial surfaces. Our study indicates that using hydrophilic surface coatings could be a promising strategy for designing immune-modulatory biomaterials for clinical applications.

Anilines Formation via Molybdenum-Catalyzed Intermolecular Reaction of Ynones with Allylic Amines.

The multi-substituted anilines are widely found in organic synthesis, medicinal chemistry and material science. The quest for robust and efficient methods to construct a diverse array of these compounds using readily accessible starting materials under simple reaction conditions is of utmost importance. Here, we report an unprecedented and efficient approach for the synthesis of 2,4-di and 2,4,6-trisubstituted anilines. With a simple molybdenum(VI) catalyst, a wide range of 2,4-di and 2,4,6-trisubstituted anilines were efficiently prepared in generally good to excellent yields from readily accessible ynones and allylic amines. The synthetic potential of this methodology was further underscored by its applications in several synthetic transformations, gram-scale reactions, and derivatization of bioactive molecules. Preliminary mechanistic studies suggested that this aniline formation might involve a cascade of aza-Michael addition, [1, 6]-proton shift, cyclization, dehydration, 6π-electrocyclization, and aromatization. This novel strategy provided a robust, simple, and modular approach for the syntheses of various valuable di- or trisubstituted anilines, some of which were otherwise challenging to access.

Anilines Formation via Molybdenum‐Catalyzed Intermolecular Reaction of Ynones with Allylic Amines

The multi‐substituted anilines are widely found in organic synthesis, medicinal chemistry and material science. The quest for robust and efficient methods to construct a diverse array of these compounds using readily accessible starting materials under simple reaction conditions is of utmost importance. Here, we report an unprecedented and efficient approach for the synthesis of 2,4‐di and 2,4,6‐trisubstituted anilines. With a simple molybdenum(VI) catalyst, a wide range of 2,4‐di and 2,4,6‐trisubstituted anilines were efficiently prepared in generally good to excellent yields from readily accessible ynones and allylic amines. The synthetic potential of this methodology was further underscored by its applications in several synthetic transformations, gram‐scale reactions, and derivatization of bioactive molecules. Preliminary mechanistic studies suggested that this aniline formation might involve a cascade of aza‐Michael addition, [1, 6]‐proton shift, cyclization, dehydration, 6π‐electrocyclization, and aromatization. This novel strategy provided a robust, simple, and modular approach for the syntheses of various valuable di‐ or trisubstituted anilines, some of which were otherwise challenging to access.

Palladium-Catalyzed Ligand-Enabled Cyclization of Substituted Aliphatic Carboxylic Acids with Allylic Electrophiles.

A palladium-catalyzed cyclization of the β-C(sp3)-H bond of aliphatic carboxylic acids with allylic electrophiles providing five-membered γ-lactones in good to excellent yields is demonstrated. An acetyl-protected aminoethyl phenyl thioether ligand is used to promote the C-H activation reaction. A diverse range of allylic electrophiles such as allyl alcohols, allyl acetates, allyl sulfones, allyl phosphonate, allyl amine, and allyl ester have been utilized for this reaction. A feasible reaction mechanism has been proposed to account for the present cyclization reaction.

Complex Sequence-Defined Heteropolymers Enable Controlled Film Growth in Layer-By-Layer Assembly.

Digitally-encoded poly(phosphodiesters) (d-PPDE) with highly complex primary structures are evaluated for layer-by-layer (LbL) assembly. To be easily decoded by mass spectrometry (MS), these digital polymers contain many different monomers: 2 coding units allowing binary encryption, 1 cleavable spacer allowing controlled MS fragmentation, and 3 mass tags allowing fragment identification. These complex heteropolymers are therefore composed of 6 different motifs. Despite this strong sequence heterogeneity, it is found that they enable a highly controlled LbL film formation. For instance, a regular growth is observed when alternating the deposition of negatively-charged d-PPDE and positively-charged poly(allyl amine hydrochloride) (PAH). Yet, in this approach, the interdistance between consecutive coded d-PPDE layers remains relatively small, which may be an issue for data storage applications, especially for the selective decoding of the stored information. Using poly(sodium 4-styrene sulfonate) (PSS) as an intermediate non-coded polyanion, it is shown that a controlled interdistance between d-PPDE layers can be easily achieved, while still maintaining a regular LbL growth. Last but not least, it is found in this work that d-PPDE of relatively small molecular weight (i.e., significantly smaller than those of PAH and PSS) still enables a controlled LbL assembly.