Phosphonates formation

Creary, X., Geiger, C.C., and Hilton, K., Mesylate derivatives of a-hydroxy phosphonates. Formation of carbocations adjacent to the diethyl phosphonate group, J. Am. Chem. Soc., 105, 2851, 1983. 

A detailed study of reactions between dialkyl phosphite anions and nitrobenzyl bromides has been described. In reactions between the halides and the phosphites (RO)2PONa in a solvent (THF, PriOH, or MeOD) the observed products (Z = 2-, 3-, or 4-nitro), apart from phosphonic diester (104), are those of reduction, (105) or (106), coupling (107), and ether formation (108). Phosphonate formation was moderate for Z = 2-nitro (R = Me), rather higher (51-97% isolated yields) for Z = 3-nitro (R = Me or Pr ), but extremely low for Z = 4-nitro (R = Me) and absent for R = Pr . In all cases when R = Me, ether formation also occurred. In cases where the yields of phosphonate were low, the yields of (107) were correspondingly high, and vice versa. Reactions performed in darkness, daylight or UV, produced little variation in the yields of phosphonate ester (R = Me) for Z = 3-nitro, but for Z = 2-nitro- or 4-nitro-, no diisopropyl phosphonates were obtained under various conditions. Probable mechanisms of reaction were discussed. ... 

The nature of any solvent and the reaction temperature can also be of some importance. For the reaction between trimethyl phosphite and bromoacetone, carried out in diethyl ether at 30 °C, in MeOH or thf at 60 °C or in the absence of a solvent at 110-120 °C the yields of dimethyl (2-oxopropyl)phosphonate were 35, 28, 55 and 45%, whilst those of dimethyl ethenyl phosphate were 30,55,30 and 55%, respectively The proportion of oxoalkylphosphonate to enol phosphate for the reaction between triethyl phosphite and bromoacetone at 150 °C is 20 80, and this ratio is reversed if the reaction is carried out in boiling diethyl ether. Sometimes a change in both solvent and halogen produces a pronounced beneficial effect with regard to phosphonate formation thus the 80 20 advantage just noted for bromoacetone in diethyl ether is raised to 90 10 for chloroacetone at 150 °C, but for iodoacetone in boiling diethyl ether it is only 10 90 ... 

Two promising observations consist of the activation of the interaction of haloketones and phosphorus(III) esters towards phosphonate formation by the presence of silver salts and also a two-step process in which a silyl ether ArC(OSiMe3)=CHR is first treated with PhI0-BF3 Et20 at -40 °C, and the resultant complex is then treated with a trialkyl phosphite, again at -40 °C, when the products are the expected 0x0 phosphonic diesters, (EtO)2P(0)CHRCOAr ... 

A similar synthetic sequence on the enantiomer 226S provided 227S. Oxidation, phosphonate formation [135], and acetal hydrolysis provided enone phosphonate 230. Condensation with the racemic dienal 231 yielded diastereomeric tetraenes 232, which corresponded to the C12-C25 fragment of pimaricin 54. 

The first of three new methods of aryl phosphonate formation involves cyclization of the triene (155) followed by oxidation. 2-Hydroxyarylphosphon-ates are formed by treatment of aryl phosphates with a strong base such as LDA or KNH2, and in substituted aromatics the isomer produced correlates with the ease of metallation at the positions ortho to the phosphate group. The third... 

H-Phosphonate formation if a phosphopeptide Use benzyl protected phosphoramidites and anhydrous t-butyl hydroperoxide for oxidation... 

The reaction has been extended to include carbanions generated from phosphonates. This is often referred to as the Horner-Wittig or Homer-Emmons reaction. The Horner-Emmons reaction has a number of advantages over the conventional Wittig reaction. It occurs with a wider variety of aldehydes and ketones under relatively mild conditions as a result of the higher nucleophilicity of the phosphonate carbanions. The separation of the olefinic product is easier due to the aqueous solubility of the phosphate by-product, and the phosphonates are readily available from the Arbusov reaction. Furthermore, although the reaction itself is not stereospecific, the majority favor the formation of the trans olefin and many produce the trans isomer as the sole product. 

Phosphoms compounds are effective flame retardants for oxygenated synthetic polymers such as polyurethanes and polyesters. Aryl phosphates and chloroalkyl phosphates are commonly used, although other compounds such as phosphonates are also effective. The phosphoms compounds can promote char formation, thereby inhibiting further ignition and providing an efficient thermal insulation to the underlying polymer. 

Phosphorus(III) Oxide. Phosphoms(III) oxide [12440-00-5] the anhydride of phosphonic acid, is formed along with by-products such as phosphoms pentoxide and red phosphoms when phosphoms is burned with less than stoichiometric amounts of oxygen (62). Phosphoms(III) oxide is a poisonous, white, wax-like, crystalline material, which has a melting point of 23.8°C and a boiling point of 175.3°C. When added to hot water, phosphoms(III) oxide reacts violentiy and forms phosphine, phosphoric acid, and red phosphoms. Even in cold water, disproportionation maybe observed if the oxide is not well agitated, resulting in the formation of phosphoric acid and yellow or orange poorly defined polymeric lower oxides of phosphoms (LOOP). 

Multilayers of Diphosphates. One way to find surface reactions that may lead to the formation of SAMs is to look for reactions that result in an insoluble salt. This is the case for phosphate monolayers, based on their highly insoluble salts with tetravalent transition metal ions. In these salts, the phosphates form layer stmctures, one OH group sticking to either side. Thus, replacing the OH with an alkyl chain to form the alkyl phosphonic acid was expected to result in a bilayer stmcture with alkyl chains extending from both sides of the metal phosphate sheet (335). When zirconium (TV) is used the distance between next neighbor alkyl chains is - 0.53 nm, which forces either chain disorder or chain tilt so that VDW attractive interactions can be reestablished. 

Sca.Ie nd Sta.in Controllers. Polyacrjiates (low molecular weight) and organic phosphonates, eg, (l-hydroxyethyhdene)diphosphonic acid, prevent or control precipitation of CaCO by acting as chelating agents (qv) or dispersants (qv) to prevent excessive formation of hard scale by promoting crystal distortion. 

Despite several attractive features in this method of direct halogen introduction and the obvious applications in the synthesis of deoxy sugars, its uses have not been further exploited by other groups of workers. Some new related methods have become available which reportedly eliminate the difficulties previously encountered such as rearrangement, unreactivity due to steric hindrance, and phosphonate ester formation. The reaction is based on the observation (28) that triethylphosphine reacts with ethanol and carbon tetrachloride to give ethyl chloride, chloroform, and triethylphosphite. In a new adaptation (76, 77) of this... 

Hydrogenation of the bicyclic aziridine-2-phosphonate 221 (Scheme 3.82) in THF resulted in the formation of piperidinephosphonate 222 in 81% yield [83]. 

Swern oxidation of N-unsubstituted aziridine-2-phosphonates resulted in the formation of both 2H-azirine-2-phosphonates and 2H-azirine-3-phosphonates [81, 83]. Treatment of ds-aziridine-2-phosphonate 226 (Scheme 3.84) with DM SO/ (COCl)2/Et3N afforded azirine-phosphonates 227 and 228, with the former predominating [81]. Under similar conditions, however, trans-aziridine-2-phospho-... 

Emulsions are frequently used in the formulation of herbicides. Such emulsions have to form stable concentrates. They will be diluted with water before applying on plants. In this form too the surfactants used have to support the formation of fine droplets at the nozzles and provide a sufficient wetting of leaves. Surfactants have to be used which will not interfere with water hardness. Therefore phosphate esters and phosphonic esters are often applied. 

The following examples illustrate the use of phosphonate terminology for esters of phosphonic acid, HP(0)(0H)2- For formation of the alternative (substitutive) names, see 2-Carb-31.2. 

Examples of the intermolecular C-P bond formation by means of radical phosphonation and phosphination have been achieved by reaction of aryl halides with trialkyl phosphites and chlorodiphenylphosphine, respectively, in the presence of (TMSlsSiH under standard radical conditions. The phosphonation reaction (Reaction 71) worked well either under UV irradiation at room temperature or in refluxing toluene. The radical phosphina-tion (Reaction 72) required pyridine in boiling benzene for 20 h. Phosphinated products were handled as phosphine sulfides. Scheme 15 shows the reaction mechanism for the phosphination procedure that involves in situ formation of tetraphenylbiphosphine. This approach has also been extended to the phosphination of alkyl halides and sequential radical cyclization/phosphination reaction. ... 

Other cyclizations at phosphorus have been observed when certain phosphinates were used in the acid-catalyzed Mannich reaction. As observed previously with various phosphonous acid derivatives, reaction of aliphatic phosphinic acids with primary amines favored the formation of 2 1 adducts (73). Thus, glycine and other a-amino acids reacted under the typical conditions with excess formaldehyde and alkyl phosphonous acids to give the bis-phosphinylmethyl adducts 125. 

The reaction of 1,2-dithiolanes with 2- and 4-picolyllithium has been examined <96PS(112)101> and the reactions of thioanhydrides such as 94 with both thiols <95JOC3964> and amines <96TL5337> have been reported. Treatment of 1,2-dithiolium salts with lithium or thallium cyclopentadienide results in formation of a variety of bi-, tri- and tetracyclic products <96LA109>. Reaction of 95 with trimethyl phosphite gives some of the desired coupling product but also the phosphonates 96 <96PS(109)557>. 

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