Α-amidoalkylation Reaction Research Articles

MATEO: intermolecular α-amidoalkylation theoretical enantioselectivity optimization. Online tool for selection and design of chiral catalysts and products.

The enantioselective Brønsted acid-catalyzed α-amidoalkylation reaction is a useful procedure is for the production of new drugs and natural products. In this context, Chiral Phosphoric Acid (CPA) catalysts are versatile catalysts for this type of reactions. The selection and design of new CPA catalysts for different enantioselective reactions has a dual interest because new CPA catalysts (tools) and chiral drugs or materials (products) can be obtained. However, this process is difficult and time consuming if approached from an experimental trial and error perspective. In this work, an Heuristic Perturbation-Theory and Machine Learning (HPTML) algorithm was used to seek a predictive model for CPA catalysts performance in terms of enantioselectivity in α-amidoalkylation reactions with R2 = 0.96 overall for training and validation series. It involved a Monte Carlo sampling of > 100,000 pairs of query and reference reactions. In addition, the computational and experimental investigation of a new set of intermolecular α-amidoalkylation reactions using BINOL-derived N-triflylphosphoramides as CPA catalysts is reported as a case of study. The model was implemented in a web server called MATEO: InterMolecular Amidoalkylation Theoretical Enantioselectivity Optimization, available online at: https://cptmltool.rnasa-imedir.com/CPTMLTools-Web/mateo . This new user-friendly online computational tool would enable sustainable optimization of reaction conditions that could lead to the design of new CPA catalysts along with new organic synthesis products.

1-Aminoalkylphosphonium Derivatives: Smart Synthetic Equivalents of N-Acyliminium-Type Cations, and Maybe Something More: A Review.

N-acyliminium-type cations are examples of highly reactive intermediates that are willingly used in organic synthesis in intra- or intermolecular α-amidoalkylation reactions. They are usually generated in situ from their corresponding precursors in the presence of acidic catalysts (Brønsted or Lewis acids). In this context, 1-aminoalkyltriarylphosphonium derivatives deserve particular attention. The positively charged phosphonium moiety located in the immediate vicinity of the N-acyl group significantly facilitates Cα-P+ bond breaking, even without the use of catalyst. Moreover, minor structural modifications of 1-aminoalkyltriarylphosphonium derivatives make it possible to modulate their reactivity in a simple way. Therefore, these types of compounds can be considered as smart synthetic equivalents of N-acyliminium-type cations. This review intends to familiarize a wide audience with the unique properties of 1-aminoalkyltriarylphosphonium derivatives and encourage their wider use in organic synthesis. Hence, the most important methods for the preparation of 1-aminoalkyltriarylphosphonium salts, as well as the area of their potential synthetic utilization, are demonstrated. In particular, the structure–reactivity correlations for the phosphonium salts are discussed. It was shown that 1-aminoalkyltriarylphosphonium salts are not only an interesting alternative to other α-amidoalkylating agents but also can be used in such important transformations as the Wittig reaction or heterocyclizations. Finally, the prospects and limitations of their further applications in synthesis and medicinal chemistry were considered.

MCDCalc: Markov Chain Molecular Descriptors Calculator for Medicinal Chemistry.

Cheminformatics models are able to predict different outputs (activity, property, chemical reactivity) in single molecules or complex molecular systems (catalyzed organic synthesis, metabolic reactions, nanoparticles, etc.). Cheminformatics models are able to predict different outputs (activity, property, chemical reactivity) in single molecules or complex molecular systems (catalyzed organic synthesis, metabolic reactions, nanoparticles, etc.). Cheminformatics prediction of complex catalytic enantioselective reactions is a major goal in organic synthesis research and chemical industry. Markov Chain Molecular Descriptors (MCDs) have been largely used to solve Cheminformatics problems. There are different types of Markov chain descriptors such as Markov-Shannon entropies (Shk), Markov Means (Mk), Markov Moments (πk), etc. However, there are other possible MCDs that have not been used before. In addition, the calculation of MCDs is done very often using specific software not always available for general users and there is not an R library public available for the calculation of MCDs. This fact, limits the availability of MCMDbased Cheminformatics procedures. We studied the enantiomeric excess ee(%)[Rcat] for 324 α-amidoalkylation reactions. These reactions have a complex mechanism depending on various factors. The model includes MCDs of the substrate, solvent, chiral catalyst, product along with values of time of reaction, temperature, load of catalyst, etc. We tested several Machine Learning regression algorithms. The Random Forest regression model has R2 > 0.90 in training and test. Secondly, the biological activity of 5644 compounds against colorectal cancer was studied. We developed very interesting model able to predict with Specificity and Sensitivity 70-82% the cases of preclinical assays in both training and validation series. The work shows the potential of the new tool for computational studies in organic and medicinal chemistry.

1-(N-Acylamino)alkyltriarylphosphonium Salts with Weakened Cα-P⁺ Bond Strength-Synthetic Applications.

The α-amidoalkylating properties of 1-(N-acylamino)alkyltriarylphosphonium salts with weakened Cα-P+ bond strength are discussed and examined. It is demonstrated that such type of phosphonium salts reacts smoothly with a diverse array of carbon- and heteroatom-based nucleophiles, including 1-morpholinocyclohexene, 1,3-dicarbonyl compounds, benzotriazole sodium salt, p-toluenesulfinate sodium salt, benzylamine, triarylphosphines, and other P-nucleophiles. Reactions are conducted at room temperature, in a short time (5–15 min) and mostly without catalysts. Simple work-up procedures result in good or very good yields of products. The structures of known compounds were established by spectroscopic methods and all new compounds have been fully characterized using 1H-, 13C-, 31P-NMR, IR spectroscopy, and high-resolution mass spectrometry. Mechanistic aspects of described transformations are also performed and discussed. It was demonstrated that unique properties make 1-(N-acylamino)alkyl-triarylphosphonium salts with weakened Cα-P+ bond strength interesting building blocks with great potential, especially in α-amidoalkylation reactions.

Phenolic Activation in Chiral Brønsted Acid-Catalyzed Intramolecular α-Amidoalkylation Reactions for the Synthesis of Fused Isoquinolines.

An organolithium addition–intramolecular α-amidoalkylation sequence on N-phenethylimides has been developed for the synthesis of fused tetrahydroisoquinoline systems using 1,1′-bi-2-naphthol (binol)-derived Brønsted acids. This transformation is the first in which activated benzene derivatives are used as internal nucleophiles, instead of electron-rich heteroaromatics, generating a quaternary stereocenter. Phenolic substitution on the aromatic ring of the phenethylamino moiety and the use of binol-derived N-triflylphosphoramides as catalysts are determinants to achieve reasonable levels of enantioselection, that is, up to 75% enantiomeric excess, in the α-amidoalkylation step. The procedure is complementary to the intermolecular α-amidoalkylation process, as opposite enantiomers are formed, and to the Pictet–Spengler cyclization, which allows the formation of tertiary stereocenters.

1,4-Phenylenebis[(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl)methanone

The compound named in the title was prepared from N1,N4-diphenethylterephthalamide 1. The resulting bis terephthalamide was subjected to an intramolecular α-amidoalkylation reaction with paraformaldehyde in the presence of heterogeneous catalyst TfOH/SiO2 to obtain 1,4-phenylenebis[(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl)methanone]. The structure of the newly synthesized compound was determined using 1H, 13C-NMR, UV, IR and mass spectral data.

Tandem synthesis of pyrroloisoquinolines through 5-endo iodolactamization, oxidative functionalization and α-amidoalkylation reaction

Pyrroloisoquinolines formation through 5-endo halocyclization of unsaturated amides, direct C–H oxidative functionalization and N-acyliminium cyclization is described. A range of β-iodo-pyrrolidinones can be efficiently synthesized using this method, making it an excellent approach for constructing natural products containing pyrrolidinones. Besides, we have developed convenient alternative routes for the synthesis of pyrroloisoquinolines in two separated steps or one pot.

Combining α-amidoalkylation reactions of N-acyliminium ions with ring-closing metathesis: access to versatile novel isoindolones spirocyclic compounds

A novel approach to diversely spirocyclic isoindoles has been developed by using N-acyliminium/ring-closing metathesis strategy. Spirocyclization precursors, diolefinic, and enyne spiro-fused-isoindole derivatives have been obtained by a regioselective reduction of the spiro-imide compounds, followed by the allylation of the N-acyliminium intermediates (generated from the acetoxylactam compounds). Ruthenium catalyzed ring-closing metathesis of the above unsaturated derivatives provided novel spiroisoindoles.

Silica-Supported Polyphosphoric Acid in the Synthesis of 4-Substituted Tetrahydroisoquinoline Derivatives

We report herein an application of an α-amidoalkylation reaction, as an alternative efficient synthesis of 4-aryl- and 4-methyl-1,2,3,4-tetrahydroisoquinoline derivatives. The amides required for this purpose would result from reaction of aminoacetaldehyde dimethylacetal with different substituted benzenes in polyphosphoric acid, followed by acylation of the obtained amines with different acid chlorides or sulfochlorides. We compared the cyclisation step using conventional (milieu of acetic-trifluoracetic acid = 4:1) and solid supported reagents (SiO2/PPA), as recovered, regenerated and reused without loss of its activity catalyst. We found that in comparison to conventional methods, the yields of the reaction are greater and the reaction time is shorter.

N-(1-acyloaminoalkyl)amidinium salts derived from DBU or related bases as reactive intermediates in α-amidoalkylation reactions

N-Acylamino)alkyltriphenylphosphonium salts 4, when treated with DBU, DBN or TBD in CD3CN or MeCN, were transformed immediately into the corresponding 1-(N- acylamino)alkylamidinium or guanidinium salts 5. Salts 5 with a proton at the α-position underwent slow transformation to the corresponding enamides 6. 1-(N- Acylamino)alkyltriphenylphosphonium salts 4, amidinium or guanidinium salts 5, as well as enamides 6 reacted readily with β-dicarbonyl compounds in the presence of corresponding base under microwave irradiation at 60 o C to give the expected product of α-amidoalkylation of the enolate anion. The role of 1-(N-acylamino)alkylamidinium or guanidinium salts 5 as reactive intermediates in α-amidoalkylation with 1-(N-acylamino)alkyltriphenylphosphonium salts is discussed.

A Multimetallic Piano-Stool Ir–Sn3 Catalyst for Nucleophilic Substitution Reaction of γ-Hydroxy Lactams through N-Acyliminium Ions

A multimetallic piano-stool complex [Cp*Ir(SnCl(3))(2){SnCl(2)(H(2)O)(2)}] (1) having Ir-Sn(3) motif has been synthesized from [Cp*IrCl(2)](2) and SnCl(2). The multimetallic complex catalytically promotes the nucleophilic substitution reaction (here after α-amidoalkylation reaction) of γ-hydroxylactams generated from phthalimidals to obtain decorated isoindolinones in excellent yields. Succinamidals, however, lead to the substituted pyrrolidinones (thermodynamic control product) via S(N)1-type path as well as eliminated pyrrolinones (kinetic control product) via an E1-type path, depending on the reaction parameters. A straightforward application of this methodology is to synthesize benzo-fused indolizidine alkaloid mimics.

Enantioselective intramolecular α-amidoalkylation reaction in the synthesis of pyrrolo[2,1-a]isoquinolines

BINOL-derived chiral Brønsted acids are capable of carrying out the intramolecular α-amidoalkylation of a tertiary N-acyliminium ions when a methoxylated benzene ring is used as internal π nucleophile. The reaction can be applied to the synthesis of pyrrolo[2,1-a]isoquinolines and use of the sterically congested acid 3e is determinant to obtain good levels of enantioselection.

Camphoric acid derived sulfur containing bicyclic carboxylic acids as chiral auxiliaries in N-acyliminium ion chemistry

Three novel sulfur containing chiral bicyclic carboxylic acids were synthesized from d-camphoric acid. Two of these compounds were briefly evaluated for their potency as chiral auxiliaries in Asymmetric Electrophilic α-Amidoalkylation (AEαA) reactions.

Stereocontrolled synthesis of enantiopure cis- and trans-3,4,4a,5,8,8a-hexahydro-1 H-quinolin-2-ones

Starting from the 8-allyl substituted oxazolopiperidone lactam 2b, which is easily accessible from ( R)-phenylglycinol and racemic δ-oxoester 1a, two-step sequences involving a stereoselective α-amidoalkylation reaction, either with inversion or retention of configuration, followed by a ring-closing metathesis, provide diastereodivergent routes to enantiopure cis- and trans-3,4,4a,5,8,8a-hexahydro-1 H-quinolin-2-ones.

Intermolecular and Intramolecular α-Amidoalkylation Reactions Using Bismuth Triflate as the Catalyst

Bismuth(III) triflate was found to promote the formation of stable cyclic N-acyliminium species in remarkable catalytic amounts (1 mol %). The alpha-amidoalkylation process seems to be effective in intermolecular and intramolecular manners leading to alpha-substituted lactams and heterocyclic systems containing azacycles, respectively. By comparing our results with those obtained with the classical Lewis acids as catalysts, it was evidenced clearly that the use of bismuth(III) triflate had been efficient for nearly all alpha-acetoxy lactams we used, except for N-acyliminium precursors bearing a sulfur atom. Also, the process seems to be easy, general, and clean, having diastereoselectivity comparable to protocols using classical Lewis acids and resulting in the formation of polyheterocyclic systems in good to excellent yields (64-99% in acetonitrile as solvent).

C-10b Functionalized 5,6-dihydropyrrolo[2,1-a]isoquinolines as intermediates in the synthesis of erythrinane systems. Intra- vs. intermolecular conjugate addition based strategies

C-10b Functionalized 5,6-dihydropyrrolo(2,1-a)isoquinolines have been prepared via Parham cyclization and α-amidoalkylation reactions, using functionalized organolithium reagents. Their utility as intermediates in the synthesis of erythrinanes via intra or intermolecular conjugate addition reactions has been studied. Thus, a protocol for preparing the erythrinane skeleton through a Parham cyclization−intermolecular α-amidoalkylation−intermolecular conjugate addition−ring-closing metathesis process has been described.

Stereoselective α-amidoalkylation of phenylglycinol-derived lactams. Synthesis of enantiopure 5,6-disubstituted 2-piperidones

The stereochemical outcome of α-amidoalkylation reactions of chiral nonracemic bicyclic lactams 2b and 2c with indole, allyltrimethylsilane, TMSCN and Grignard reagents to gain access to enantiopure 5,6-disubstituted 2-piperidones is discussed.

Diastereoselective Intramolecular α-Amidoalkylation Reactions of l-DOPA Derivatives. Asymmetric Synthesis of Pyrrolo[2,1-a]isoquinolines

[reaction: see text] Stereocontrolled intramolecular alpha-amidoalkylation reactions of L-DOPA-derived succinimides have been studied. Addition of MeLi to nonracemic succinimides 9a-d yields oxoamides, which are cyclized upon treatment with Lewis or protic acids to afford (5S,10bS)-trans 11 or (5S,10bR)-cis 12pyrroloisoquinolines with variable diastereoselectivities, but with high enantiomerical purities (ee 99%).

A Practical Approach to the Fused β‐Carboline System. Asymmetric Synthesis of Indolo[2,3‐a]indolizidinones via a Diastereoselective Intramolecular α‐Amidoalkylation Reaction.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Stereoselective Synthesis of 1-Substi- tuted 1,2,3,4-Tetrahydro-b-carbolines by Asymmetric Electrophilic a-Amido- alkylation Reactions

An efficient procedure for the asymmetric synthesis of 1-substituted 1,2,3,4-tetrahydro-9-methyl-β-carbolines based on asymmetric electrophilic α-amidoalkylation reactions is described. Stereoselective addition of variousorganometallic reagents to a chiral N-acyl-β-carbolinium ion gave the corresponding 1-substituted 1,2-dihydro-β-carbolines in high yields and very good to excellent diastereomeric ratios. Catalytic hydrogenation followed by the removal of the chiral auxiliary via reductive cleavage of the amide bond proceeded with complete conservation of the absolute configuration at the newly created stereocenter leading to 1-substituted 1,2,3,4-tetrahydro-9-methyl-β-carboline derivatives in high yields. Their absolute stereochemistry was proven by X-Ray analysis. The 1-phenyl-substituted 1,2,3,4-tetrahydro-β-carbolines were evaluated for their affinity to the PCP binding site of the NMDA receptor.