Mechanism of Phosphorus-Carbon Bond Formation in the Amidoalkylation of Phosphonous Carboxylic Acids

Phosphate adsorption from water and wastewater using non-devulcanised and devulcanised tyre rubber

The secondary use of tyre rubber is a potentially sustainable environmental solution. However, the sorption properties of used-tyre rubber have not yet been fully investigated. In this study, the rubber type (vulcanised or devulcanised part-worn tyre rubber) that can sorb phosphate phosphorus from aqueous solutions or wastewater more effectively is determined. The capacity of granules (0.3-1.0 mm in diameter) of non-devulcanised ground tyre rubber and uniquely chemically devulcanised rubber to adsorb phosphorus is evaluated under laboratory conditions. The results show that under the filtration of an aqueous solution or biologically treated wastewater at a flow rate of 0.75 m/h (1.2 L/h), 1 g of the devulcanised rubber medium accumulates 5.16 mg of phosphorus, which is five times more than that accumulated by the non-devulcanised rubber medium. The surface structure of the non-devulcanised rubber medium is more suitable for the sorption of devulcanised rubber granules. The sorption capacity and effectiveness of non-devulcanised rubber for phosphorus removal are more favourable compared with those of the tested natural and waste-prepared sorbents. Further research into this material as a medium for filter layers and for accumulating drainage should be conducted. The findings of this study are important for addressing issues associated with the secondary use of tyre rubber.

Metal-Free Phosphination and Continued Functionalization of Pyridine: A Theoretical Study

This study investigates the mechanism of metal-free pyridine phosphination with P(OEt)₃, PPh₃, and PAr₂CF₃ using density functional theory calculations. The results show that the reaction mechanism and rate-determining step vary depending on the phosphine and additive used. For example, phosphination of pyridine with P(OEt)₃ occurs in five stages, and ethyl abstraction is the rate-determining step. Meanwhile, 2-Ph-pyridine phosphination with PPh₃ is a four-step reaction with proton abstraction as the rate-limiting step. Energy decomposition analysis of the transition states reveals that steric hindrance in the phosphine molecule plays a key role in the site-selective formation of the phosphonium salt. The mechanism of 2-Ph-pyridine phosphination with PAr₂CF₃ is similar to that with PPh₃, and analyses of the effects of substituents show that electron-withdrawing groups decreased the nucleophilicity of the phosphine, whereas aryl electron-donating groups increased it. Finally, TfO⁻ plays an important role in the C–H fluoroalkylation of pyridine, as it brings weak interactions.

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.

A One-Pot Approach to 2-Substituted-2-(Dimethoxyphosphoryl)-Pyrrolidines from Substituted tert-Butyl 4-Oxobutylcarbamates and Trimethyl Phosphite

A novel approach to 2-substituted-2-(dimethoxyphosphoryl)-pyrrolidines 7a-7o and 9a-9r has been developed, which features a TMSOTf-mediated one-pot intramolecular cyclization and phosphonylation of substituted tert-butyl 4-oxobutylcarbamates. The major advantages of this method include simple operation under mild reaction conditions, the use of cheap Lewis acid, and good to excellent yields with high diastereoselectivities (dr up to 99:1).

A Carbodiimide-Mediated P-C Bond-Forming Reaction: Mild Amidoalkylation of P-Nucleophiles by Boc-Aminals

The first example of a carbodiimide-mediated P-C bond-forming reaction is described. The reaction involves activation of β-carboxyethylphosphinic acids and subsequent reaction with Boc-aminals using acid-catalysis. Mechanistic experiments using ³¹P NMR spectroscopy and DFT calculations support the contribution of unusually reactive cyclic phosphinic/carboxylic mixed anhydrides in a reaction pathway involving ion-pair "swapping". The utility of this protocol is highlighted by the direct synthesis of Boc-protected phosphinic dipeptides, as precursors to potent Zn-aminopeptidase inhibitors.