An Efficient Synthesis of Anilinobenzylphosphonates

One-pot synthesis of α-aminophosphonates by yttrium-catalyzed Birum-Oleksyszyn reaction

For the first time, yttrium triflate was used as an efficient green catalyst for the synthesis of α-aminophosphonates through a one-pot three-component Birum–Oleksyszyn reaction. Under the action of this Lewis acid, enhancement of the yield and reaction chemoselectivity was provided by the achievement of an appropriate balance in the complex network of reactions.

For the first time, yttrium triflate was used as an efficient green catalyst for the synthesis of α-aminophosphonates through a one-pot three-component Birum–Oleksyszyn reaction.

Functionalization of α-hydroxyphosphonates as a convenient route to N-tosyl-α-aminophosphonates

Direct conversion of the α-hydroxyl group by para-toluenesulfonamide to yield α-(N-tosyl)aminophosphonates is reported. α-Aminophosphonates 23a,b-37a,b were obtained from the corresponding α-hydroxyphosphonates 6a,b-21a,b in the presence of K₂CO₃, via the retro-Abramov reaction of the appropriate aldehydes, 1-5. The subsequent formation of imines with simultaneous addition of diethyl phosphite provided access to the α-sulfonamide phosphonates 23a,b-37a,b with better diastereoselectivity than in the case of the Pudovik reaction. The mechanism for this transformation is proposed herein. When Cbz N-protected aziridine 9a,b and phenylalanine analogue 12a,b were exploited, intramolecular substitution was observed, leading to the corresponding epoxide 38 as the sole product, or oxazolidin-2-one 39 as a minor product. Analogous substitution was not observed in the case of proline 18a,b and serine 21a,b derivatives.

Recent developments on ultrasound assisted catalyst-free organic synthesis

Mother Nature needs to be protected from ever increasing chemical pollutions associated with synthetic organic processes. The fundamental challenge for today's methodologists is to make their protocols more environmentally benign and sustainable by avoiding the extensive use of hazardous reagents and solvents, harsh reaction conditions, and toxic metal catalysts. However, the people of the twenty-first century are well aware about the side effects of those hazardous substances used and generated by the chemical processes. As a result, the last decade has seen a tremendous outburst in modifying chemical processes to make them 'sustainable' for the betterment of our environment. Catalysts play a crucial role in organic synthesis and thus they find huge applications and uses. Scientists' continuously trying to modify the catalysts to reduce their toxicity level, but the most benign way is to design an organic reaction without catalyst(s), if possible. It is worthy to mention that the involvement of ultrasound in organic synthesis is sometimes fulfilling this goal. In many occasions the applications of ultrasound can avoid the use of catalysts in organic reactions. Such beneficial features as a whole have motivated the organic chemists to apply ultrasonic irradiation in more heights and as a results, in recent past, there were immense applications of ultrasound in organic reactions for the synthesis of diverse organic scaffolds under catalyst-free condition. The present review summarizes the latest developments on ultrasound assisted catalyst-free organic synthesis reported so far.

The synthesis of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides by the microwave-assisted Pudovik reaction

A family of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides was synthesized by the microwave-assisted solvent-free addition of dialkyl phosphites and diphenylphosphine oxide, respectively, to imines formed from benzaldehyde derivatives and primary amines. After optimization, the reactivity was mapped, and the fine mechanism was evaluated by DFT calculations. Two α-aminophosphonates were subjected to an X-ray study revealing a racemic dimer formation made through a N-H···O=P intermolecular hydrogen bridges pair.

Catalyst-free ultrasonic-promoted multicomponent synthesis of tertiary α-amino phosphonates

A highly efficient and green protocol has been developed for the synthesis of novel tertiary α-amino phosphonates via a catalyst-free multi-component Kabachnik–Fields reaction under ultrasound irradiation.

Design, synthesis, antioxidant, and anti-breast cancer activities of novel diethyl(alkyl/aryl/heteroarylamino)(4-(pyridin-2-yl)phenyl)methylphosphonates

A series of new diethyl(alkyl/aryl/heteroarylamino)(4-(pyridine-2-yl)phenyl)methylphosphonates (4a-t) were synthesized via three-component Kabachnik-Field's reaction of 4-(pyridin-2-yl)benzaldehyde, diethylphosphite and various primary amines, catalyzed by cupric acetate monohydrate [Cu(OAc)(2) ∙ H(2)O] under solvent-free and microwave irradiation conditions. Their computational docking analysis supported them as good therapeutic agents to the breast cancer aromatase enzyme and ascertained 4a, 4h, 4m, 4n, and 4t as potential molecules with good binding affinities varying from -9.0 to -9.6 kcal/mol and containing the 4-(pyridine-2-yl)phenyl moiety as a pharmacophore. Their in vitro screening performed for the anti-cell proliferation activity against MBC-MCF7 cells by MTT and Trypan blue assays confirmed 4m, 4n, and 4q as promising compounds to sustain a low percentage of cell viability at 20 µg/mL concentration. These compounds were also evaluated for their antioxidant activity by the DPPH method and the results established that compounds 4m, 4n, and 4q show around 10% higher activity than the standard antioxidant ascorbic acid.

Ionic liquid promoted synthesis, antibacterial and in vitro antiproliferative activity of novel α-aminophosphonate derivatives

Ionic liquid ethyl ammonium nitrate is used as an excellent catalyst and solvent for three-component one-pot reaction of an aldehydes, amines and diethylphosphite to form novel α-aminophosphonates at room temperature. Among the various catalysts, the preparation of ethyl ammonium nitrate is an environmental friendly, cost effective and recyclable catalyst. Compounds 4b, 4c, 4d, 4f and 4j were found more potent antibacterials against pathogenic microorganisms. Whereas, compounds 4a, 4g, 4h and 4j inhibits growth of active Escherichia coli NCIM 2645 and Salmonella typhi NCIM 2501. Compound 4j was found a promising antiproliferative agent against A549 and SK-MEL2 human melanoma cell lines.

Design, Synthesis, and Antifungal Activity of New α-Aminophosphonates

α-Aminophosphonates are bioisosteres of amino acids and have several pharmacological activities. These compounds have been synthesized by various routes from reaction between amine, aldehyde, and phosphite compounds. In order to synthesize α-aminophosphonates, catalytic effect of CuCl₂ was compared with FeCl₃. Also all designed structures as well as griseofulvin were docked into the active site of microtubule (1JFF), using Autodock program. The results showed that the reactions were carried out in the presence of CuCl₂ in lower yields, and also the time of reaction was longer in comparison with FeCl₃. The chemical structures of the new compounds were confirmed by spectral analyses. The compounds were investigated for antifungal activity against several fungi in comparison with griseofulvin. An indole-derived bis(α-aminophosphonates) with the best negative ΔG in docking study showed maximum antifungal activity against Microsporum canis, and other investigated compounds did not have a good antifungal activity.

Solvent-free synthesis of pyrimidine nucleoside-aminophosphonate hybrids and their biological activity evaluation

A novel and highly efficient one-pot three-component synthesis of alpha-aminophosphonates under neat condition was developed. By employing this method, hybrid compounds of aminophosphonate with pyrimidine nucleosides were synthesized in good to excellent yields starting from 5-formyl-2'-deoxyuridine, aniline and dimethyl phosphite. The antiviral and antileishmanial activities of these novel hybrid compounds were also studied but none were found to be active.