Synthesis of amidomethyltrifluoroborates and their use in cross-coupling reactions

Asymmetric Total Syntheses of ent-Stachybotrin C and Its Congener

The asymmetric total syntheses of ent-stachybotrin C and its congener have been accomplished through a convergent approach in the longest linear sequence of 12 steps from commercially available materials, respectively. Noteworthy transformation of the synthesis involved a cascade Knoevenagel condensation/Hantzsch ester reduction/epoxide ring-opening/transetherification to construct the core pyran ring with two adjacent stereocenters.

Ru Doped Hydrotalcite Catalyzed Borrowing Hydrogen-Mediated N-Alkylation of Benzamides, Sulfonamides, and Dehydrogenative Synthesis of Quinazolinones

An efficient Ru doped hydrotalcite catalyzed N-alkylation of benzamides and sulfonamides with alcohols via borrowing hydrogen catalysis is illustrated. Various primary alcohols, including benzyl, heteroaryl, and aliphatic alcohols, were alkylated in good to excellent yields. To shed light on the mechanistic details, several control studies and deuterium labeling experiments were performed. Mechanistic studies underpin that the reaction is going via a borrowing hydrogen pathway rather than an S_N1 type mechanism. The reaction can be easily scaled up without any detrimental effect on the yield. The catalyst is also capable of synthesizing quinazolinone directly from 2-aminobenzamide and alcohols. Successful recyclability and high reactivity highlight the practical applicability of the catalyst.

Regioselective Amidomethylation of 4-Chloro-3-fluoropyridine by Metalation and Minisci-Type Reactions

The synthesis of a series of 2-amidomethylated pyridines (3-8) was investigated, starting from 4-chloro-3-fluoropyridine. Kinetic deprotonation at -75 °C followed by reaction with DMF gave 2-formyl-4-chloro-3-fluoropyridine 10 regioselectively, which was converted to 2-aminomethyl analogue 1 via sulfinamide 2. Alternatively, Minisci-type amidomethylation under Ag⁺/persulfate or photoredox-mediated conditions using a series of amino acid derivatives gave (3-8, 19, and 34) in 30-74% yield and isomer ratios in the range 6.7:1 to >50:1. The latter methods gave overall yields similar to that of the deprotonation approach, but were shorter and more amenable to scale-up. In particular, N-Boc analogue 8 was obtained in a single step. The amidomethylations of another six 3-fluoropyridines under the photoredox conditions were briefly examined.

Nickel-Catalyzed Phosphine Free Direct N-Alkylation of Amides with Alcohols

Herein, we developed an operational simple, practical, and selective Ni-catalyzed synthesis of secondary amides. Application of renewable alcohols, earth-abundant and nonprecious nickel catalyst facilitates the transformations, releasing water as byproduct. The catalytic system is tolerant to a variety of functional groups including nitrile, allylic ether, and alkene and could be extended to the synthesis of bis-amide, antiemetic drug Tigan, and dopamine D2 receptor antagonist Itopride. Preliminary mechanistic studies revealed the participation of a benzylic C-H bond in the rate-determining step.

2-Azadienes as Reagents for Preparing Chiral Amines: Synthesis of 1,2-Amino Tertiary Alcohols by Cu-Catalyzed Enantioselective Reductive Couplings with Ketones

We introduce a new strategy for synthesis of chiral amines: couplings of α-aminoalkyl nucleophiles generated by enantioselective migratory insertion of 2-azadienes to a Cu-H. In this report, we demonstrate its application in catalytic reductive coupling of 2-azadienes and ketones to furnish 1,2-amino tertiary alcohols with vicinal stereogenic centers.

Synthesis of Aminoboronic Acid Derivatives from Amines and Amphoteric Boryl Carbonyl Compounds

Herein, we demonstrate the use of α-boryl aldehydes and acyl boronates in the synthesis of aminoboronic acid derivatives. This work highlights the untapped potential of boron-substituted iminium ions and offers insights into the behavior of N-methyliminodiacetyl (MIDA) boronates during condensation and tautomerization processes. The preparative value of this contribution lies in the demonstration that various amines, including linear and cyclic peptides, can be readily conjugated with boron-containing fragments. A mild deprotection of amino MIDA-boronates enables access to α- and β-aminoboronic acids in high chemical yields. This simple process should be applicable to the synthesis of a wide range of bioactive molecules as well as precursors for cross-coupling reactions.

Synthesis of α-aminoboronic acids

This review describes available methods for the preparation of α-aminoboronic acids in their racemic or in their enantiopure form. Both, highly stereoselective syntheses and asymmetric procedures leading to the stereocontrolled generation of α-aminoboronic acid derivatives are included. The preparation of acyclic, carbocyclic and azacyclic α-aminoboronic acid derivatives is covered. Within each section, the different synthetic approaches have been classified according to the key bond which is formed to complete the α-aminoboronic acid skeleton.

α-Arylation/Heteroarylation of Chiral α-Aminomethyltrifluoroborates by Synergistic Iridium Photoredox/Nickel Cross-Coupling Catalysis

Direct access to complex, enantiopure benzylamine architectures using a synergistic iridium photoredox/nickel cross-coupling dual catalysis strategy has been developed. New C(sp(3))-C(sp(2)) bonds are forged starting from abundant and inexpensive natural amino acids.

Facile synthesis of borofragments and their evaluation in activity-based protein profiling

The discovery of enzyme inhibitors relies on synthetic methods that enable rapid and modular construction of small molecules. Heterocyclic fragments designed to maximize enthalpic interactions with their protein targets represent a particularly desirable class of molecules. Here we describe a reagent that enables straightforward construction of "borofragments", in which a heterocycle is separated from the boron center by two or three rotatable bonds. The stability of these molecules depends on the MIDA group which likely acts as a slow-release element under biological conditions. Borofragments can be used to discover inhibitors of enzymes that use catalytic oxygen nucleophiles. We have employed this method to identify inhibitors of ABHD10 and the predicted carboxypeptidase CPVL. This technique should be applicable to other classes of targets.

Combination of gold and iridium catalysts for the synthesis of N-alkylated amides from nitriles and alcohols

An alternative and efficient approach for the synthesis of N-alkylated amides from nitriles and alcohols was proposed and accomplished.

MnO2 catalyzed formylation of amines and transamidation of amides under solvent-free conditions

A facile and efficient MnO₂ catalyzed one-pot protocol for formylation of amine and transamidation of primary and secondary amides by amines has been developed.

An efficient mechanochemical synthesis of amides and dipeptides using 2,4,6-trichloro-1,3,5-triazine and PPh3

A mechanochemical method for amidation of carboxylic acids and urethane-protected (Fmoc, Cbz, Boc) α-amino acids has been developed as a facile, efficient, and eco-friendly route toward amides and dipeptides.

Convergent, asymmetric synthesis of vicinal amino alcohols via Rh-catalyzed addition of α-amido trifluoroborates to carbonyls

The convergent, asymmetric synthesis of vicinal amino alcohols is achieved by the Rh-catalyzed addition of α-amido trifluoroborates to carbonyl compounds.

Reaction-based and single fluorescent emitter decorated ratiometric nanoprobe to detect hydrogen peroxide

A novel reaction-based cross-linked polymeric nanoprobe with a self-calibrating ratiometric fluorescence readout to selectively detect H2O2 is reported. The polymeric nanoprobe is fabricated by using hydrophobic H2O2-reactive boronic ester groups, crosslinker units, and environmentally sensitive 3-hydroxyflavone fluorophores through a miniemulsion polymerization. On treatment with H2O2, the boronic esters in the polymer are cleaved to form hydrophilic alcohols and subsequently lead to a hydrophobic-hydrophilic transition. Covalently linked 3-hydroxyflavones manifest the change in polarity as a ratiometric transition from green to blue, accompanied by a 500-fold increase in volume. Furthermore, this nanoprobe has been used for ratiometric sensing of glucose by monitoring the H2O2 generated during the oxidation of glucose by glucose oxidase, and thus successfully distinguished between normal and pathological levels of glucose.

Pd-catalyzed Suzuki-Miyaura cross-coupling reactions between sulfamates and potassium Boc-protected aminomethyltrifluoroborates

Sulfamates were studied as the electrophilic partners in the palladium-catalyzed Suzuki-Miyaura cross-coupling reaction with potassium Boc-protected primary and secondary aminomethyltrifluoroborates. A broad range of substrates was successfully coupled to provide the desired products. Complex molecules containing a new carbon-carbon bond and an aminomethyl moiety could be prepared through this developed method.

Direct synthesis of amides from carboxylic acids and amines using B(OCH2CF3)3

B(OCH₂CF₃)₃, prepared from readily available B₂O₃ and 2,2,2-trifluoroethanol, is as an effective reagent for the direct amidation of a variety of carboxylic acids with a broad range of amines. In most cases, the amide products can be purified by a simple filtration procedure using commercially available resins, with no need for aqueous workup or chromatography. The amidation of N-protected amino acids with both primary and secondary amines proceeds effectively, with very low levels of racemization. B(OCH₂CF₃)₃ can also be used for the formylation of a range of amines in good to excellent yield, via transamidation of dimethylformamide.

Synthesis of Imides and Benzoylureas by Direct Oxidation of N-methylenes of Amides and Benzylureas

Some amides and benzylureas can be oxidised to imides and benzoylureas, respectively, using silver(I) nitrate (20 mol %), copper(II) sulfate pentahydrate (20 mol %), ammonium persulfate (3.0 equiv.), and potassium fluoride (20 equiv.) in water at room temperature.

Synthesis and biological evaluation of 4-(aminomethyl)-1-hydroxypyrazole analogues of muscimol as γ-aminobutyric acid(a) receptor agonists

A series of bioisosteric 4-(aminomethyl)-1-hydroxypyrazole (4-AHP) analogues of muscimol, a GABA(A) receptor agonist, has been synthesized and pharmacologically characterized at native and selected recombinant GABA(A) receptors. The unsubstituted 4-AHP analogue (2a) (EC(50) 19 μM, R(max) 69%) was a moderately potent agonist at human α(1)β(2)γ(2) GABA(A) receptors, and in SAR studies substitutions in the 3- and/or 5-position were found to be detrimental to binding affinities. Ligand-receptor docking in an α(1)β(2)γ(2) GABA(A) receptor homology model along with the obtained SAR indicate that 2a and muscimol share a common binding mode, which deviates from the binding mode of the structurally related antagonist series based on 4-(piperidin-4-yl)-1-hydroxypyrazole (4-PHP, 1). Selectivity for α(1)β(2)γ(2) over ρ(1) GABA(A) receptors was observed for the 5-chloro, 5-bromo, and 5-methyl substituted analogues of 2a illustrating that even small differences in structure can give rise to subtype selectivity.

Potassium Boc-protected secondary aminomethyltrifluoroborates: synthesis and Suzuki-Miyaura cross-coupling reactions

Seven potassium Boc-protected secondary aminomethyltrifluoroborates were prepared in a standardized two-step process. The Suzuki-Miyaura cross-coupling reaction was studied with this new class of nucleophiles, and a large variety of aryl and hetaryl chlorides provided the desired products in good to excellent yields, thereby allowing easy access to secondary aminomethyl substructures.

Rapid and efficient access to secondary arylmethylamines

Ammoniomethyl trifluoroborates are very powerful reagents that can be used to access biologically relevant aryl- and heteroaryl-methylamine motifs via Suzuki-Miyaura cross-couplings. Until now, this method was limited to the production of tertiary and primary amines. The synthesis of a large array of secondary ammoniomethyltrifluoroborates has been achieved through a one step nucleophilic substitution reaction on the potassium bromomethyltrifluoroborate. Smooth cross-coupling conditions have been designed, based on the use of an aminobiphenyl palladium precatalyst, to couple these trifluoroborates efficiently with aryl bromides. This strategy offers a new way to access biologically relevant motifs and allows, with the previously developed methods, access to all three classes of aminomethylarenes.

Synthesis and cross-coupling reactions of imidomethyltrifluoroborates with aryl chlorides

Potassium imidomethyltrifluoroborate salts were efficiently synthesized. Potassium phthalimidomethyl-trifluoroborate was successfully used in Suzuki-Miyaura-like cross-coupling reactions with a variety of aryl chlorides.

Palladium-catalyzed direct hydroxymethylation of aryl halides and triflates with potassium acetoxymethyltrifluoroborate

Suzuki-Miyaura cross-coupling reactions of aryl halides and triflates with potassium acetoxymethyltrifluoroborate afforded the corresponding aryl and heteroaryl methanol products in moderate to excellent yields.

Iridium-Catalyzed Allylic Amination Route to α-Aminoboronates: Illustration of the Decisive Role of Boron Substituents

The development of a new route to α-aminoboronates using an iridium-catalyzed allylic amination on boronated substrates is described. Unlike the boronate group, the trifluoroborato substituent was found to govern the regioselectivity exclusively in favor of branched products. The transformation of an allylic substitution product into an α-aminoboronic ester in an efficient way validated the implementation of this approach.

Synthesis and Suzuki-Miyaura cross-coupling reactions of potassium Boc-protected aminomethyltrifluoroborate with aryl and hetaryl halides

Potassium Boc-protected aminomethyltrifluoroborate, a primary aminomethyl equivalent, was synthesized successfully through a "one-pot" process. With this trifluoroborate, Suzuki-Miyaura cross-coupling reactions were investigated with a variety of both aryl and hetaryl chlorides in good to excellent yields.

Reinvestigation of aminomethyltrifluoroborates and their application in Suzuki-Miyaura cross-coupling reactions

A reinvestigation into the chemical composition of potassium aminomethyltrifluoroborates is reported. These trifluoroborato salts have been reassigned as zwitterionic ammoniomethyltrifluoroborates. Minor adjustments to the previously disclosed reaction conditions are reported that permit a similar level of activity as nucleophiles in Suzuki-Miyaura cross-coupling reactions.

Cross-coupling of mesylated phenol derivatives with potassium ammonio- and amidomethyltrifluoroborates

A large array of aryl and heteroaryl mesylates have been successfully employed as electrophiles in a Csp(2)-Csp(3) Suzuki-Miyaura cross-coupling with potassium ammonio- and amidomethyltrifluoroborates to afford the corresponding products in high yields.

Synthesis and cross-coupling of sulfonamidomethyltrifluoroborates

Sulfonamidomethyltrifluoroborates were successfully synthesized and cross-coupled with a wide range of aryl and heteroaryl chlorides, allowing the construction of a sulfonamidomethyl aryl linkage through a new disconnection, thus offering a new way to access such structurally interesting motifs.