Dialkyl aryl phosphonates

Et or Bu) and the phosphonation of iodoaromatics with dialkyl phosphonates, although in this case with poorer yields (better results of the dialkyl arylphosphonates are obtained by photostimulation). Chemical oxidation (using AgNO -peroxodi-sulphate) and anodic oxidation of aromatics in the presence of trialkyl phosphites produces dialkyl arylphosphonates in good yields. The Cul-catalysed arylation of dialkyl (cyanomethyl)-phosphonates affords dialkyl (a-cyanobenzyl)phosphonates. ... 

Palladium-catalyzed cross-coupling reactions of diaryliodonium tetrafluo-roborates have recently been employed for conversions of mercaptans to aryl-and diaryl sulfides, sodium arenesulfinates to diaryl sulfones, and dialkyl phosphites to aryl phosphonates (Scheme 43) [120-122]. 

The LDA catalyzed rearrangement of dialkyl aryl phosphates (99) to dialkyl (2-hydroxyaryl)- phosphonates has been known for some time and the use of the di-tert-butyl esters, now reported, offers advantages in the ease of preparation of the respective free (2-hydroxyaryl)phosphonic acids. The sequence (Scheme 7) has also been extended to include further phosphorylation and rearrangement steps to yield the 2,6-bis(dialkoxyphosphinyl)phenols (100). ... 

Suzuki, H., Watanabe, K. and Qui, Y, Copper(I) iodide-mediated arylation of dialkyl cyanomethane-phosphonates. A novel route to a-arylated aUcanenitriles, Chem. Lett.. 1779, 1985. 

Alkyl ethers of dialkyl (hydroxymethyl)phosphonic acid have been obtained by a modified Arbuzov procedure in the presence of BF3 Et20, triethyl phosphite reacts with the formals ROCH20Ar according to Scheme 16 the reactions are best carried out in the presence of TiCl4 at -78 °C, but the Lewis acid catalyst and the experimental conditions have to be chosen carefully, otherwise mixed alkyl aryl esters are produced. Boron trifluoride etherate also catalyses the interaction of acetals of 4-substituted benzaldehydes with triethyl phosphite to give diethyl (a-alkoxybenzyl)phosphonates. Both aliphatic and aromatic aldehydes are reported to react with trialkyl phosphites at 100 °C to give the ethers 204 ... 

The additions of thiols and sulphenyl chlorides to alkenylphosphonic derivatives to yield (2-alkylthioethyl)phosphonic compounds are reactions which have already been noted" Dialkyl (alkylthiomethyl)phosphonates yield a-chloro derivatives when treated with ncs in CCl/° the resultant dialkyl (l-alkylthio-l-chloromethyl)phosphonates undergo Friedel-Crafts arylation with benzene, alkylbenzenes or other activated aromatics in the presence of SnCl4 or TiCl/ yields are said to be good. 

The first Pd -catalyzed P-arylation of dialkyl phosphites with arylboro-nic acids or aryl trifluoroborates has been carried out by using palladium acetate, the rigid bidentate ligand dmphen (dmphen = 2,9-dimethyl-1,10-phenanthroline), and without addition of a base or acid. The arylated phosphonates (512) were isolated in 44-90% yields (Scheme 132). 

Silver carbonate catalyzes the carbon phosphonation of aryl propiolates with dialkyl H-phosphonates in order to prepare 3-phosphonated conma-rins (140L3356). Other propiolates undergo copper(II)-mediated direct trifluoromethylation with Togni s reagent 19 providing 3-trifluoromethyl-coumarins (Scheme 54) (14OL4240). 

It was shown that dialkyl arylphosphonates were prepared in good yield by the reaction of aryl iodides or bromides with dialkyl H-phosphonates in the presence of triethylamine and a catalytic amount of tetrakis(triphenylphosphine)palladium [368],... 

Phosphonic acid can generate phosphomonoester, phosphodiester, and phos-photriester because phosphonic acid contains three -OH. Phosphotriester has no collecting performance. Dialkyl and aryl phosphonates also have no collecting performance. The flotation performances of decoyl and octyl phos-phomonoesters are relatively better in the flotation of cassiterite. 

Feringa and coworkers reported a copper-catalyzed O-arylation of dialkyl phosphonates and phosphoramidates with diaryliodonium triflates and 2,6-di-ferf-butylpyridine (DTBP), giving easy access to mixed alkyl aryl phosphonates via elimination of one of the alkyl groups as the alkyl triflate prior to arylation (Scheme 10a) [133]. Aryl(mesityl)iodonium salts reacted in a chemoselective way. Copper-catalyzed arylations of hydroxamic acids [134] and carboxylic acids [135] have also been reported, the latter utilizing thiophosphoramides as cooperative catalysts to allow arylation at room temperature. Onomura s group discovered a Cu-catalyzed monoarylation of vicinal diols in toluene at 100 °C. Only traces of product were obtained with alcohols lacking the vicinal hydroxyl group [136]. 

Many representatives of the trialkyl orthophosphate ester, dialkyl alkyl (or aryl) phosphonate ester, alkyl dialkyl (or diaryl)-phosphinate, and trialkyl (or triaryl) phosphine oxide class have been investigated. Judging from the reviews available, none of the more exotic types appears to offer any particular advantage over tributyl orthophosphate as a selective extractant for resolving lanthanide mixtures. Most are either viscous liquids or solids that require a diluent, and for the most part the individual separation factors to be had are unspectacular. 

Trialkyl esters of phosphonic acid exist ia two structurally isomeric forms. The trialkylphosphites, P(OR)2, are isomers of the more stable phosphonates, 0=PR(0R)2, and the former may be rearranged to resemble the latter with catalytic quantities of alkylating agent. The dialkyl alkylphosphonates are used as flame retardants, plasticizers, and iatermediates. The MichaeUs-Arbusov reaction may be used for a variety of compound types, including mono- and diphosphites having aryl as weU as alkyl substituents (22). Triaryl phosphites do not readily undergo the MichaeUs-Arbusov reaction, although there are a few special cases. 

The palladium-catalysed cross-coupling of aryl halides or vinyl halides with dialkyl phosphonates (31) to yield dialkyl arylphosphonates and dialkyl vinylphosphonates, respectively, was first reported by Hirao and co-workers 69 the halides used most frequently are bromides and the reaction is stereospecific with haloalkenes. Subsequently, analogous reactions of alkyl alkylphosphinates (32), alkyl arylphosphinates (32), alkyl phosphinates (33), and secondary phosphine oxides (34), replacing [P—H] bonds with [P—C] bonds to yield various phosphinates and tertiary phosphine oxides, have been developed (Figure 7.1). Alkyl phosphinates (33) may be mono- or diarylated as desired by the selection of appropriate conditions. Aiyl and vinyl triflates have also found limited... 

Koh, Y.J., and Oh, D.Y, A new synthesis of P-keto phosphonate from aryl epoxysulfones and dialkyl hydrogen phosphite. Tetrahedron Lett., 34, 2147, 1993. 

The ready alkylation of sodium phosphonate carbanions with chloro- or bromoacetates in THF provides a useful access to dialkyl 2-(alkoxycarbonyl)ethylphosphonates bearing a variety of alkyl, aryl, cyano, keto, or phosphoryl groups at the cx-carbon (Scheme 8.43). By using a chiral auxiliary, the alkylation of phosphorus-stabilized benzylic carbanions with bromoacetate proceeds with high diastereoselectivity to provide an easy access to optically active alkylphosphonic acids. ... 

Preparations of aromatic phosphonates containing alkoxycarbonyl groups have been developed by the Pd(0)-catalyzed reaction of aryl bromides or aryl triflates with dialkyl phosphites. Although these two procediues employ the same catalyst, Pd(PPh3)4, at the same temperature in the presence of tertiary amine, the use of triflates increases reaction rates and yields (Scheme 8.68). ... 

Tavs, P, Reaction of aryl hahdes with trialkyl phosphites and dialkyl benzenephosphonites to aromatic phosphonates and phosphinates by nickel salt catalysed arylation, Chem. Ber., 103, 2428, 1970. 

Dialkyl [2-chloro-2-(1-cyclohexenyl)ethenyl]phosphonates with alkyl (or aryl) sulphenyl chlorides afford derivatives of che bicyclic 5,6,7,8,9,10-hexahydro-2H-l,2-benzoxaphosphorin (205) rather than spirocyclic 1,2-oxaphospholes. ... 

Other Studies. - The P NMR chemical shifts of alcohols, carboxylic acids and phenols phosphitylated with 2-chloro-4,4,5,5-tetramethyl-dioxaphospholane have been correlated with substituent effects of phenols. P NMR spectroscopy has also been used to study activation pathways of aryl H-phosphonate ester condensation reactions, the conversion of allenyl and divinyl phosphines to 1- and 2-phosphadienes, the reaction of tetraphosphorus decasulfide with dialkyl disulfides, the reaction of phosphine with cyclic olefins, the chemical shift tensors of powder samples of phosphole derivatives, the reactions of alcohols and mercaptans with tetraphosphorus trichalcogen diiodides, the structure of aminomethanebisphosphonic acids, and reactions of 00-di-(2-ethylhexyl)dithiophosphoric acids. ... 

Alkyl esters of phosphonous and phosphinous acid also react readily y with carbon tetrachloride, while analogous aryl esters, e.g., EtP(OPh)2, are resistant even at 160° (152,173). The reaction of bromotrichloro-methane with triethyl phosphite, which occurs smoothly at 80° to furnish dialkyl trichloromethylphosphonate in excellent yield (99%), is light catalyzed. Chloroform is unchanged in the presence of triethyl phosphite (98,156) even under drastic conditions, and diethyl dichloro-methylphosphonate is not produced unless a free radical initiator is present (118). 

The hydrolysis of tervalent phosphorus acid derivatives with two P—C bonds leads to secondary phosphine oxides (50) and with one P—C bond to phosphonus acid derivatives (51). Chlorophosphines react rapidly with water, but aminophosphines, phosphinites and phosphonites often survive a short wash with aqueous NaHC03, an effective way to remove contaminating ammonium salts in the crude products. However, aminophosphines with small substituents, e.g. dimethylaminodimethylphosphine, aryl phosphinites and phosphonites and trimethylsilyl phosphinites and phosphonites are hydrolysed too quickly for such a treatment. The hydrolyses are catalysed by acids (the hydrolyses of phosphinites and phosphonites are also catalysed by OH ) and are much faster than hydrolyses of the corresponding phosphoryl compounds [up to a factor of 10 for acid-catalysed hydrolysis of (MeO)3P compared with (MeO)3P=0 ]. Dialkyl phosphonites are rapidly hydrolysed to the monoalkyl esters (51, X = OR) in weakly acidic water, whereas hydrolyses to phosphonous acids require reflux with strong acid or base, e.g. equation 131 Bis-(dialkylamino) phosphines may also be partially hydrolysed to phosphonous acid amides (51, X = NR2). Tervalent phosphorus acid derivatives with hydrogen sulphide give secondary phosphine sulphides or phosphonodithious acids, e.g. equation 156 . ... 

Cul was later found to catalyse the phosphonation of aryl halides (bromides or iodides) by dialkyl hydrogenphosphonates in hmpa ... 

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