Phosphonates aminophosphonates

Separation and purification of microquantities of scandium (III) from macroquantities of rare earths on selective ion-exchangers has been described by Hubicki (1990). The chelating and ion-exchangers examined include phosphonic gel and macroporous, aminophos-phonic, various carboxylic, amino-acids with different matrix compositions, polyphenol, amphoteric (snake in cage polymers), cellulose phosphate, zirconium phosphate, and copolymer of polystyrene with divinylbenzene. The phosphonic, aminophosphonic and cellulose-phosphate were the most effective. 

Symmetrical cyclic triazines (masked imines) have been used in reaction with diethyl trimethylsilyl phosphite to provide phosphonates bearing silyl-substituted a-aminophosphonates.349... 

Gadolinium(III) complexes containing phosphonate groups can be targeted to bone. Examples are the DOTA derivatives (325, 326) and complexes of aminophosphonate ligands (327). 

Fluorinated a-aminophosphonates containing two pendent alkene chains with catalyst la led to six- or seven-membered cyclic phosphonates as potential antibacterial reagents [36] (Sciieme 8.4). 

If additional catalysts are used, both acids and bases can have a positive influence on the reaction rate. Sometimes, the chemical yield and the diastereoselectivity of the formation of a-aminophosphonates are higher in two-component systems using preformed imines. In this case, due to the phosphonate <-> phosphite tautomerism, the addition to the imine could occur by either a four- or five-membered transition state ... 

Addition of the lithium anion of chloromethylphosphonate to sulfinimine 126 gave a-chloro-P-aminophosphonates 195 in a ratio of 59 41 and 98% total yield.104 The diastereomeric products can be separated and each converted to the corresponding aziridine-2-phosphonates 196, new building chiral blocks for the enantioselective synthesis of a-aminophosphonates 197 and azirinyl phosphonates 198.104... 

N,0 donor molecules where the carboxylic acid group is replaced by another acid group such as sulfonic or phosphonic acid may also chelate efficiently, such as aminophosphonic... 

Catalytic hydrogenation (Pd-on-carbon) of N-Boc aziridine 2-phosphonates (253) derived from 3-amino-2-hydroxyphosphonates affords N-Boc a-aminophosphonic esters (254) in high enantiomeric purity (Scheme 68). 

Condensations. Alumina promotes the formation of a-hydroxyphosphonate esters from aromatic aldehydes and dialkyl phosphonates, and the adducts are converted to a-aminophosphonate esters on reaction with ammonia. A solvent-free synthesis of a-nitro ketones comprises mixing nitroalkanes, aldehydes, and neutral alumina and oxidizing the adducts with wet, alumina-supported CrOj (15 examples, 68-86%). The Knoevenagel reaction, the Michael addition of nitromethane to gcm-diactivated alkenes, and the formation of iminothiazolines from thioureas and a-halo ketones are readily effected with alumina under microwave irradiation. 

The Rh" acetate catalysed decomposition of dimethyl a-diazobenzylpl-ospho-nate (204) in the presence of primary amines and amides offers a simple route to the corresponding a-aminophosphonates. 1-Aminocycloalkylphosphonates 205 have been synthesised from the corresponding cycloalkylphosphonate via electrophilic azidation of the phosphonate carbanion followed by catalytic hydrogenation. ... 

Schrader, T., Kober, R., and Steglich. W., Synthesis of l-aminophosphonic acid derivatives via (acylimino)phosphonic esters. Synthesis. 372, 1986. 

Some reports describe the nucleophilic attack at the cyano carbon atom of DECP without P-CN bond splitting. For example, the cycloaddition of lithium trimethylsUyldiazomethane and nitrile oxides to the cyano group of DECP produces 1,2,3-triazole and l,2,4-oxadiazole-4-phosphonates, respectively. In the presence of a Lewis acid, which increases the electrophilicity of the cyano carbon atom, compounds containing active methylene groups add to the cyano group to give a,P-unsaturated oc-aminophosphonates (Scheme 6.46). ... 

The additions of dialkyl phosphites and secondary phosphine sulphides to Schiff bases have been used to prepare a-aminophosphonates and tertiary phosphine sulphides, respectively. Trialkyl phosphites react readily with (AT-phenylbenzimidoyl)formic acid (25) to give the phosphonate (26) and the formate (27). Alternative mechanisms, both involving initial... 

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