The Stereochemical Course of the α‐Hydroxyphosphonate–Phosphate Rearrangement

The phosphonate–phosphate rearrangement is an isomerisation of α‐hydroxyphosphonates bearing electron‐withdrawing substituents at the α‐carbon atom. We studied the stereochemical course of this rearrangement with respect to phosphorus. A set of four diastereomeric α‐hydroxyphosphonates was prepared by a Pudovik reaction from two diastereomeric cyclic phosphites. The hydroxyphosphonates were separated and rearranged with Et₃N as base. In analogy to trichlorphon, which was the first reported compound undergoing this rearrangement. All four hydroxyphosphonates could be rearranged to 2,2‐dichlorovinyl phosphates. Single‐crystal X‐ray structure analyses of the α‐hydroxyphosphonates and the corresponding phosphates allowed us to show that the rearrangement proceeds with retention of configuration on the phosphorus atom.     

α‐Aminophosphonates and α‐Aminophosphine Oxides by the Microwave‐Assisted Kabachnik–Fields Reactions of 3‐Amino‐6‐methyl‐2 H‐pyran‐2‐ones

The microwave‐assisted Kabachnik–Fields reaction of a series of 3‐amino‐6‐methyl‐2H‐pyran‐2‐ones, paraformaldehyde, and dialkyl phosphites or diphenylphosphine oxide led to α‐aminophosphonates or α‐aminophosphine oxides, respectively. The α‑aminophosphonates were obtained under solvent‐free conditions, whereas the α‑aminophosphine oxides in acetonitrile. The novel products were characterized by NMR and mass spectral data. © 2013 Wiley Periodicals, Inc. Heteroatom Chem 24:221–225, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21086     

Synthesis and properties of novel α‐(1,2,4‐triazolo[1,5‐a]pyrimidine‐2‐oxyl)phosphonate derivatives

In an attempt to discover novel compounds with high activity and low toxicity, a series of new phosphonate derivatives containing triazolo[1,5‐a]pyrimidine moieties have been designed and synthesized by a nucleophilic substitution between α‐hydroxyphosphonates and 2‐methanesulfonyl‐1,2,4‐triazolo[1,5‐a]pyrimidines. The structures of all compounds prepared were confirmed by elemental analyses and by NMR and MS spectroscopy. The results of preliminary bioassay indicate that the title compounds possess certain selective herbicidal activity against rape and also, to some extent, inhibit of acetolactase synthase activity. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:313–316, 2000     

A novel hydrophobic copper complex supported on γ‐Fe2O3 as a magnetically heterogeneous catalyst for one‐pot three‐component synthesis of α‐aminophosphonates

A novel hydrophobic copper complex supported on γ‐Fe₂O₃ is synthesized and characterized by different methods such as FT‐IR, XRD, TEM, SEM, TGA, VSM, ICP and CHN analysis. It was used as a magnetically recyclable heterogeneous catalyst for the efficient synthesis of α‐aminophosphonates via a one‐pot three‐component reaction under solvent‐free conditions. The present catalytic system worked extremely well for the synthesis of α‐aminophosphonates even up to five subsequent trails without significant loss of its catalytic activity or copper leaching. The TEM image and FT‐IR spectrum of the catalyst after five times recovery showed that the structure of the catalyst was stable under the reaction conditions with no change being observed. The strong magnetic properties of the reused catalyst were revealed by complete and easy attraction using an external magnet and also by VSM curve. This work represents the first and unique example of a hydrophobic copper complex for catalysis in water generating reactions.     

Synthesis and structure of new types of organogermanium compounds containing α‐amino acid or α‐aminophosphonic acid moieties

A series of germasesquioxides and germatranes containing α‐amino acid or α‐aminophosphonic acid moieties was synthesized by the reaction of β‐trichlorogermylpropionyl chloride with α‐amino acid esters or α‐aminophosphonates. The structures of all products were confirmed by ¹H NMR, ³¹P NMR, and IR spectra, and elemental analyses. The intramolecular monocyclic penta‐coordinated structure of the trichlorogermyl intermediate was determined by X‐ray diffraction. The X‐ray analyses showed that the geometry about the germanium atom was a slightly distorted trigonal bipyramid, and a coordinate covalent bond exists between the oxygen and the germanium atoms. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 73–78, 1999     

Synthesis of O,O‐Diphenyl N‐trichlorogermanylpropiono‐α‐aminophosphonates

A variety of novel O,O‐Diphenyl N‐(trichlorogermanyl)propiono‐α‐aminophosphonates were synthesized by the reaction of β‐(trichlorogermanyl) propionyl chloride with diphenyl α‐aminophosphonates in the presence of triethylamine. The structures of all of the products were confirmed by ¹H‐NMR spectroscopy, elemental analyses, and IR spectroscopy. Data of ¹H‐NMR and IR spectroscopic determinations indicated the title compounds to be pentacoordinated organogermanium compounds. The results of bioassay showed that some of the title compounds possess potential anticancer activity. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 5–8, 1999     

An Eco‐friendly Three Component Manifold for the Synthesis of α‐Aminophosphonates under Catalyst and Solvent‐free Conditions,X‐ray Characterization and Their Evaluation as Anticancer Agents

A series of α‐aminophosphonates were synthesized through one‐pot condensation of aryl aldehydes, aryl amines and diethyl phosphite in the absence of any catalyst and organic solvents. All the synthesized α‐aminophosphonates were characterized by spectral and elemental analysis and in the case of compound 4j by X‐ray crystallography. Some of these new α‐aminophosphonate derivatives were found to have cytotoxic activity on the cancer cell line DU145 in vitro by the MTT method.     

Unsaturated cyclic α‐hydroxyphosphonates

In an attempt to find novel plant growth regulators, a series of unsaturated cyclic α‐hydroxyphosphonates were synthesized by the addition reactions of 4‐aryl‐5,5‐dimethyl‐1,3,2‐dioxaphosphinane 2‐oxides with 5‐aryl‐2E,4E‐pentadienaldehydes. The cis and trans isomers of the products were isolated. The structures of all products were confirmed by elemental analyses and by NMR and IR spectroscopy or MS. The results of preliminary bioassay indicate that the title compounds possess potential inhibitory activity on the elongation of wheat coleoptile. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:266–268, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10039     

Phosphosulfonic acid‐catalyzed green synthesis and bioassay of α‐aryl‐α′‐1,3,4‐thiadiazolyl aminophosphonates

A series of new α‐aminophosphonates containing 1,3,4‐thiadiazole moiety (4a–l) were synthesized via a simple, efficient, and one‐pot three‐component Kabachnik–Fields reaction of 2‐amino‐5‐ethyl‐1,3,4‐thiadiazole with various aryl/heteroaryl aldehydes and diethylphosphite under solvent‐free microwave irradiation conditions using phosphosulfonic acid, as a reusable and heterogeneous solid acid catalyst. All the title compounds were screened for radical scavenging activity by DPPH and H₂O₂ methods, and antimicrobial activity against bacteria (Gram‐positive and Gram‐negative) and fungi using the disc diffusion technique. They exhibited potent in vitro antioxidant and moderate antimicrobial activity.     

A facile and efficient synthesis of diethyl α,α‐chlorofluoroalkanephosphonates

A facile and efficient synthetic methodo‐ logy for the preparation of diethyl α,α‐chlorofluoro‐ alkanephosphonates is described. A wide variety of diethyl α‐hydroxyphosphonates were investigated by a two‐step halogenation procedure, which includes nucleophilic chlorination with PPh₃ and CCl₄ and electrophilic fluorination with N‐fluorobisbenzene‐ sulfonimide. Aromatic and aliphatic α,α‐chlorofluoro‐ phosphonates could be prepared by this method with acceptable yields. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:250–255, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20604     

Stereodivergent Dual Catalytic α‐Allylation of Protected α‐Amino‐ and α‐Hydroxyacetaldehydes

Fully stereodivergent dual‐catalytic α‐allylation of protected α‐amino‐ and α‐hydroxyacetaldehydes is achieved through iridium‐ and amine‐catalyzed substitution of racemic allylic alcohols with chiral enamines generated in situ. The operationally simple method furnishes useful aldehyde building blocks in good yields, more than 99 % ee, and with d.r. values greater than 20:1 in some cases. Additionally, the γ,δ‐unsaturated products can be further functionalized in a stereodivergent fashion with high selectivity and with preservation of stereochemical integrity at the C_α position.     

An Efficient Green Synthesis of a New Class of α‐Aminophosphonates under Microwave Irradiation Conditions in the Presence of PS/PTSA

The present work focuses on the study of catalytic activity of polystyrene‐supported p‐toluenesulfonic acid (PS/PTSA) and the synthesis of α‐aminophosphonates from the Kabachnik–Fields (KF) reaction under microwave irradiation in solvent‐free conditions. Recently, the catalytic activity of PS/PTSA was tested with good yields. This procedure is the simplest, most straightforward, environment friendly method for the synthesis of α‐aminophosphonates from simple to different substituted aldehyde substrates. Furthermore, this catalyst can be recovered and reused without loss of its catalytic activity.     

SO3H‐functionalized ionic liquids catalyzed the synthesis of α‐aminophosphonates in aqueous media

SO₃H‐functionalized halogen‐free ionic liquids were prepared and used as efficient and recyclable catalysts for the synthesis of α‐aminophosphonates at room temperature via the one‐pot three‐component condensation reaction in aqueous media with good yields of 80–96%. The postprocessing was simple, and the catalysts could be reused at least six times without noticeably decreasing the catalytic activity. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:546–550, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20644     

A Quick and Clean Procedure for Synthesis of α‐Aminophosphonates in Aqueous Media

A green and efficient procedure for the synthesis of α‐aminophosphonates has been developed in water as a green and nonhazardous solvent, from condensation between aromatic aldehydes, aniline, and triphenyl phosphite at 80°C. This methodology has a number of advantages including clean reaction conditions, easy work‐up, and environmentally friendly.     

P‐Dodecylbenzenesulfonic Acid: A Highly Efficient Catalyst for One‐Pot Synthesis of α‐Aminophosphonates in Aqueous Media

A highly efficient one‐pot three‐component reaction of aldehydes or ketones, amines, and trimethyl or triethyl phosphite catalyzed by p‐dodecylbenzensulfonic acid is developed for the synthesis of α‐aminophosphonates at room temperature in water. © 2013 Wiley Periodicals, Inc. Heteroatom Chem 24:174–178, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21079     

NbCl5: an efficient catalyst for one‐pot synthesis of α‐aminophosphonates under solvent‐free conditions

NbCl₅ has been found to be a very effective catalyst for the synthesis of a variety of α‐aminophosphonates through the Kabachnik–Fields reaction of carbonyl compound, amine and diethyl phosphite under solvent‐free conditions. Copyright © 2010 John Wiley & Sons, Ltd.     

Radical Cation Salt‐initiated Aerobic C−H Phosphorylation of N‐Benzylanilines: Synthesis of α‐Aminophosphonates

A radical cation salt‐initiated phosphorylation of N‐benzylanilines was realized through an aerobic oxidation of the sp³ C?H bond, providing a series of α‐aminophosphonates in high yields. An investigation of the reaction scope revealed that this mild catalyst system is superior in good functional group tolerance and high reaction efficiency. The mechanistic study implied that the cleavage of the sp³ C?H bond was involved in the rate‐determining step.     

Asymmetric and Geometry‐Selective α‐Alkenylation of α‐Amino Acids

Both E‐ and Z‐N′‐alkenyl urea derivatives of imidazolidinones may be formed selectively from enantiopure α‐amino acids. Generation of their enolate derivatives in the presence of K⁺ and [18]crown‐6 induces intramolecular migration of the alkenyl group from N′ to Cα with retention of double bond geometry. DFT calculations indicate a partially concerted substitution mechanism. Hydrolysis of the enantiopure products under acid conditions reveals quaternary α‐alkenyl amino acids with stereodivergent control of both absolute configuration and double bond geometry.     

Facile Preparation of α‐Cyano‐α,ω‐Diaryloligovinylenes: A New Class of Color‐Tunable Solid Emitters

An efficient Knoevenagel condensation reaction was used to construct a series of α‐cyano‐α,ω‐diaryloligovinylenes, which show prominent fluorescence emission in the solid state. On investigating the effect of conjugation length on fluorescent properties, we found that the diene structure showed superior solid‐state luminescence. Furthermore, the emission color could be adjusted by introducing donor or acceptor functional groups at the terminal aryl groups. Full‐color emission in the visible region can be achieved by adding different functional groups to the α‐cyano‐α,ω‐diaryldivinylene moiety. The structure–property relationships were elucidated and some observations such as the substitution position effects were discussed. These compounds have potential applications as full‐color solid emissive candidates in material science and their simple structures allow them to be easily modified resulting in further interesting properties.     

Efficient synthesis of α‐aminophosphonates via one‐pot reactions of aldehydes,amines, and phosphates in ionic liquid

Ionic liquids such as 1,3‐dialkylimidazolium bromides make excellent solvents for synthesis of α‐aminophosphonates from aldehydes, amines, and phosphites. The ionic liquids are successfully regenerated and reused. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:625–629, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20724