A copper-catalyzed Petasis reaction for the synthesis of tertiary amines and amino esters

The Petasis Reaction: Applications and Organic Synthesis-A Comprehensive Review

The Petasis reaction has introduced significant advancements through the use of various catalysts, solvents, methodologies, and substrates in diverse areas of chemistry, including medicinal, organic, combinatorial, biochemical, and heterocyclic chemistry. It is a prominent method for synthesizing compounds such as α-amino acids, β-amino alcohols, Aza-beta-lactams, alkylaminophenols, α-arylglycines, 2H-chromenes, aminophenols, and hydrazide alcohols. With the increasing demand for medicines, drugs, industrial products, insecticides, and pesticides, the Petasis reaction has become an indispensable and versatile tool. This review explores the range of reaction components, key mechanisms, and reaction conditions associated with the Petasis reaction. Additionally, the paper delves into the potential future directions of this reaction and highlights its various applications.

Recent Trends in the Petasis Reaction: A Review of Novel Catalytic Synthetic Approaches with Applications of the Petasis Reaction

The Petasis reaction, also called the Petasis Borono-Mannich reaction, is a multicomponent reaction that couples a carbonyl derivative, an amine and boronic acids to yield substituted amines. The reaction proceeds efficiently in the presence or absence of a specific catalyst and solvent. By employing this reaction, a diverse range of chiral derivatives can easily be obtained, including α-amino acids. A broad substrate scope, high yields, distinct functional group tolerance and the availability of diverse catalytic systems constitute key features of this reaction. In this review article, attention has been drawn toward the recently reported methodologies for executing the Petasis reaction to produce structurally simple to complex aryl/allyl amino scaffolds.

Rhodium(III)-catalyzed three-component C(sp2)-H activation for the synthesis of amines

Rhodium-catalyzed three-component C-H bond activation of aromatics with amides and aldehydes to synthesize amines was established. The addition of copper was found to be essential to ensure the high reactivity. The mechanistic studies indicated that key intermediates formed by the transmetallization between rhodium and copper could further promote the addition between 2-(pyridin-2-yl)-phenyl-metal species and imines. A series of densely substituted amines could be conveniently prepared by this one-step, three-component procedure from commercially available substrates via C-H bond activation with water as the only by-product.

Multicomponent Reactions (MCRs) with o-Quinone Methides

This article presents a comprehensive overview of multicomponent reactions (MCRs) that proceed via ortho-quinone methide intermediates (o-QM) generated in the reaction medium. Examples of applications involving these highly reactive intermediates in organic synthesis and biological processes (e. g., biosynthetic pathways, prodrug cleavage and electrophilic capture of biological nucleophiles) are also described. QMs are often generated by eliminative processes of phenol derivatives or by photochemical reactions, including reversible generation in photochromic substances. This class of compounds can undergo various reaction types, including nucleophilic attack at the methide carbon, with subsequent rearomatization, and react with electron-rich dienophiles in inverse-electron demand hetero-Diels-Alder reactions. Its versatile reactivity has been explored in the context of cascade reactions for the construction of several classes of substances, including complex natural products.

Synthesis of skeletally diverse β-lactam haptens for the in vitro diagnosis of IgE-mediated drug allergy

We present the first synthesis of β-lactam-derived haptens, leveraging the principles of diversity-oriented synthesis to discover compounds for drug allergy in vitro testing. We designed, synthesized, and performed in vitro...

Petasis vs. Strecker Amino Acid Synthesis: Convergence, Divergence and Opportunities in Organic Synthesis

α-Amino acids find widespread applications in various areas of life and physical sciences. Their syntheses are carried out by a multitude of protocols, of which Petasis and Strecker reactions have emerged as the most straightforward and most widely used. Both reactions are three-component reactions using the same starting materials, except the nucleophilic species. The differences and similarities between these two important reactions are highlighted in this review.

Petasis adducts of tryptanthrin – synthesis, biological activity evaluation and druglikeness assessment

The first example of a tryptanthrin-based Petasis multicomponent reaction is reported, with one of the new derivatives showing moderate fungicidal activity.

Preparation of α-amino acids via Ni-catalyzed reductive vinylation and arylation of α-pivaloyloxy glycine

This work emphasizes easy access to α-vinyl and aryl amino acids via Ni-catalyzed cross-electrophile coupling of bench-stable N-carbonyl-protected α-pivaloyloxy glycine with vinyl/aryl halides and triflates. The protocol permits the synthesis of α-amino acids bearing hindered branched vinyl groups, which remains a challenge using the current methods. On the basis of experimental and DFT studies, simultaneous addition of glycine α-carbon (Gly) radicals to Ni(0) and Ar–Ni(ii) may occur, with the former being more favored where oxidative addition of a C(sp²) electrophile to the resultant Gly–Ni(i) intermediate gives a key Gly–Ni(iii)–Ar intermediate. The auxiliary chelation of the N-carbonyl oxygen to the Ni center appears to be crucial to stabilize the Gly–Ni(i) intermediate.

We have developed Ni-catalyzed reductive coupling of N-carbonyl protected α-pivaloyloxy glycine with Csp²-electrophiles that enabled facile preparation of α-amino acids, including those bearing hindered branched vinyl groups.

Translation of the copper/bipyridine-promoted Petasis reaction to solid phase-coupled DNA for encoded library synthesis

The Petasis three-component reaction gives rise to diverse substituted α-aryl glycines from readily available amines, boronic acids and glyoxalic acid. Thus, this reaction is highly attractive for DNA-encoded small molecule screening library synthesis. The Petasis reaction is for instance promoted by a potentially DNA damaging copper(I)/bipyridine reagent system in dry organic solvents. We found that solid phase-coupled DNA strands tolerated this reagent system at elevated temperature allowing for synthesis of diverse substituted DNA-tagged α-aryl glycines from DNA-conjugated secondary amines.

Phenylboronic Acid-polymers for Biomedical Applications

Background:

Phenylboronic acid-polymers (PBA-polymers) have attracted tremendous attention as potential stimuli-responsive materials with applications in drug-delivery depots, scaffolds for tissue engineering, HIV barriers, and biomolecule-detecting/sensing platforms. The unique aspect of PBA-polymers is their interactions with diols, which result in reversible, covalent bond formation. This very nature of reversible bonding between boronic acids and diols has been fundamental to their applications in the biomedical area.

Methods:

We have searched peer-reviewed articles including reviews from Scopus, PubMed, and Google Scholar with a focus on the 1) chemistry of PBA, 2) synthesis of PBA-polymers, and 3) their biomedical applications.

Results:

We have summarized approximately 179 papers in this review. Most of the applications described in this review are focused on the unique ability of PBA molecules to interact with diol molecules and the dynamic nature of the resulting boronate esters. The strong sensitivity of boronate ester groups towards the surrounding pH also makes these molecules stimuli-responsive. In addition, we also discuss how the re-arrangement of the dynamic boronate ester bonds renders PBA-based materials with other unique features such as self-healing and shear thinning.

Conclusion:

The presence of PBA in the polymer chain can render it with diverse functions/ relativities without changing their intrinsic properties. In this review, we discuss the development of PBA polymers with diverse functions and their biomedical applications with a specific focus on the dynamic nature of boronate ester groups.

Reactivity and Synthetic Applications of Multicomponent Petasis Reactions

The Petasis boron-Mannich reaction, simply referred to as the Petasis reaction, is a powerful multicomponent coupling reaction of a boronic acid, an amine, and a carbonyl derivative. Highly functionalized amines with multiple stereogenic centers can be efficiently accessed via the Petasis reaction with high levels of both diastereoselectivity and enantioselectivity. By drawing attention to examples reported in the past 8 years, this Review demonstrates the breadth of the reactivity and synthetic applications of Petasis reactions in several frontiers: the expansion of the substrate scope in the classic three-component process; nonclassic Petasis reactions with additional components; Petasis-type reactions with noncanonical substrates, mechanism, and products; new asymmetric versions assisted by chiral catalysts; combinations with a secondary or tertiary transformation in a cascade- or sequence-specific manner to access structurally complex, natural-product-like heterocycles; and the synthesis of polyhydroxy alkaloids and biologically interesting molecules.

Tandem N, N-Dialkylation Reaction of N-Trimethylsilyl α-Iminoesters Utilizing an Umpolung Reaction and Characteristics of the Silyl Substituent: Synthesis of Pyrrolidine, Piperidine, and Iminodiacetate

Umpolung reactions of N-trimethylsilyl α-iminoester with organometallics gave directly N-alkylaminoesters in high yields without the need for removing a protecting group at the nitrogen atom. Efficient syntheses of pyrrolidines, piperidines, and iminodiacetate derivatives were also developed via tandem N,N- or N, C-dialkylation reactions utilizing characteristics of the silyl substituent. Furthermore, under the influence of silica gel, the addition of an enolate to the imino nitrogen proceeded to give an iminodiacetate derivative.

Copper-Catalyzed Asymmetric Arylation of N-Heteroaryl Aldimines: Elementary Step of a 1,4-Insertion

Copper complexes of monodentate phosphoramidites efficiently promote asymmetric arylation of N-azaaryl aldimines with arylboroxines. DFT calculations and experiments support an elementary step of 1,4-insertion in the reaction pathway, a step in which an aryl-copper species adds directly across four atoms of C=N-C=N in the N-azaaryl aldimines.

Petasis three-component reactions for the synthesis of diverse heterocyclic scaffolds

The Petasis three-component reaction (PR) of hydroxy aldehydes, amines and boronic acids is an important multi-component reaction for the synthesis of structurally diverse scaffolds and biologically interesting small molecules. The reaction has been significantly explored in the past decade, and many new variants have emerged, such as asymmetric, traceless and four-component approaches. The excellent stereoselectivity, high yield and broad functional group tolerance altogether make this reaction ideal for fragment and compound collection synthesis, since orthogonal chemical handles can be incorporated for subsequent scaffold formation and appendage modification. Herein we present a selection of recent variations on the PR theme for the synthesis of scaffolds of relevance to medicinal chemistry.

The acid promoted Petasis reaction of organotrifluoroborates with imines and enamines

The acid promoted addition of organotrifluoroborate salts to imine and enamine electrophiles is reported. Use of the pre-activated trifluoroboronate complex bypasses the need for α-hetero substitution on the electrophile component, greatly expanding the scope of the Petasis borono-Mannich reaction. A variety of vinyl, aromatic and heteroaromatic trifluoroborate salts undergo addition with good efficiency under mild reaction conditions. The reaction is amenable for use with a variety of carbamate protected imine and enamine electrophiles, achieving for the first time the effective coupling with aliphatic aldehydes.

Oxidative cross-coupling reaction by scandium catalysis for synthesis of α-alkyl α-amino acid ester derivatives

A novel oxidative cross-coupling reaction between N-arylglycine esters and alkyl boronic acid esters was developed by scandium catalysis.

Sonochemistry – an innovative opportunity towards a one-pot three-component synthesis of novel pyridylpiperazine derivatives catalysed by meglumine in water

An unprecedented and expeditious synthetic strategy for rapid access to a diversity-oriented library of novel functionalized pyridyl piperazine derivatives is reported.

Palladium-Catalyzed Enantioselective Three-Component Synthesis of α-Arylglycines

A general Pd-catalyzed, enantioselective three-component synthesis of α-arylglycines starting from sulfonamides, glyoxylic acid derivatives, and boronic acids was developed. This operationally straightforward procedure enables the preparation of a wide variety of α-arylglycines in high yields and excellent levels of enantioselectivity from a simple set of readily available starting materials. Incorporation of Pbf-amides gives a racemization-free access to N-unprotected α-arylglycines.

Rapid synthesis of alkylaminophenols via the Petasis borono–Mannich reaction using protonated trititanate nanotubes as robust solid–acid catalysts

The Petasis borono–Mannich reaction was applied to the synthesis of alkylaminophenols from o-hydroxybenzaldehydes, secondary amines and boronic acids in the presence of H₂Ti₃O₇ nanotubes as reusable solid–acid catalysts.

Multicomponent domino reactions of hydrazinecarbodithioates: concise access to 3-substituted 5-thiol-1,3,4-thiadiazolines

Two classes of addition/cycloaddition cascade reactions of hydrazinecarbodithioate (1) have been developed under mild reaction conditions. Reaction of hydrazinecarbodithioate (1) with formaldehyde solution (2) and propiolic acid (3) gives 3-propargyl-5-thiol-2,3-dihydro-1,3,4-thiadiazoles (5) via a decarboxylative coupling/cycloaddition domino sequence. When propiolic acid (3) is switched to phenyl boronic acid (4), a petasis/cycloaddition domino reaction is instead observed, in which 3-benzyl-5-thiol-2,3-dihydro-1,3,4-thiadiazoles (6) are obtained. Both these reactions show a wide range of functional-group compatibility for propiolic acids and aryl boronic acids, and give the corresponding products in moderate to good yields.

Palladium-Catalyzed Enantioselective Three-Component Synthesis of α-Substituted Amines

The first general palladium-catalyzed, enantioselective three-component synthesis of α-arylamines starting from sulfonamides, aldehydes, and arylboronic acids has been developed. These reactions generate a wide array of α-arylamines with high yields and enantioselectivities. Notably, this process is tolerant to air and moisture, providing an operationally simple approach for the synthesis of chiral α-arylamines.

Aminocatalytic cross-coupling approach via iminium ions to different C - C Bonds

Given the attractive ability of iminium ions to functionalize molecules directly at ostensibly unreactive positions, the reactivity of iminium ions, in which an α CH2 group is replaced by CO was explored. Background studies on the ability of such iminium cations to promote reactions via an iminium-catalyzed or iminium-equivalent pathway are apparently unavailable. Previously, tandem cross-coupling reactions were reported, in which an iminium ion undergoes nucleophilic 1,2-addition to give a putative three-component intermediate that abstracts a proton in situ and undergoes self-deamination followed by unprecedented DMSO/aerobic oxidation to generate α-ketoamides. However, later it was observed that iminium ions can generate valuable α-ketoamides through simple aerobic oxidation. In all reactions, iminium ions were generated in situ by reaction of 2-oxoaldehydes with secondary amines.

Synthesis of tertiary propargylamines via a rationally designed multicomponent reaction of primary amines, formaldehyde, arylboronic acids and alkynes

A novel approach for the synthesis of tertiary propargylamines is achieved through a Cu(OAc)₂-catalyzed multicomponent reaction of primary amines, formaldehyde, arylboronic acids and alkynes.

Regio- and stereocontrolled access to γ-boronated unsaturated amino esters and derivatives from (Z)-alkenyl 1,2-bis(boronates)

The Borono-Mannich reaction of (Z)-1-alkene-1,2-diboronic esters proceeded regioselectively at the terminal C-B bond to afford (E)-γ-boronated unsaturated amino esters in good yields. These compounds were then subjected to Suzuki couplings for the creation of diversely substituted olefinic amino acid systems. Several other functional transformations were also carried out to illustrate the synthetic utility of the Petasis products.

A Lewis acid palladium(II)-catalyzed three-component synthesis of α-substituted amides

A Lewis acid palladium-catalyzed reaction of amides, aryl aldehydes, and arylboronic acids is described. This new method allows for a practical and general synthesis of α-substituted amides from simple, readily available building blocks.

Arylglycine-derivative synthesis via oxidative sp(3) C-H functionalization of α-amino esters

An efficient method for the synthesis of arylglycine derivatives is described. The oxidative coupling reactions of naphthols and phenols with α-amino esters proceeded smoothly in the presence of meta-chloroperoxybenzoic acid as an oxidant under ambient conditions, to produce arylglycine derivatives in satisfactory yields.