Pyridines phosphites

Unfortunately, the good receptivity of the copper isotopes can only be applied to diamagnetic compounds and the chemistry of Cu is limited. The quadrupolar relaxation corresponding to a quite large linewidth factor further reduces the scope. Thus only tetrahedral CUL4 give sufficiently narrow lines which have been observed for L = NCMe, pyridine, phosphite, or phosphine. No resonance... 

Phosphorus trichloride reacts readily with three equivalents of an alcohol e.g, ethanol, in the presence of a tertiary amine such as pyridine, dimethyl-aniline, or diethylaniline, to form triethyl phosphite and hydrogen chloride, the latter being immediately neutralised by the tertiary amine. 

Organophosphorus Derivatives. Neopentyl glycol treated with pyridine and phosphorus trichloride in anhydrous dioxane yields the cycHc hydrogen phosphite, 5,5-dimethyl-l,3-dioxaphosphorinane 2-oxide (2) (32,33). Compounds of this type maybe useful as flameproofing plasticizers, stabilizers, synthetic lubricants, oil additives, pesticides, or intermediates for the preparation of other organophosphoms compounds (see Flame retardants Phosphorus compounds). 

Phosphite esters are formed readily by the reaction of phosphoms haUdes and isopropyl alcohol. Eor example, triisopropyl phosphite [116-17-6] is prepared from phosphoms trichloride [7719-12-2] and isopropyl alcohol at low temperatures ia the presence of an acid scavenger, eg, pyridine [110-86-1]. 

CP can also be prepared by the reaction of cellulose with phosphoms oxychloride in pyridine (37) or ether in the presence of sodium hydroxide (38). For the most part these methods yield insoluble, cross-linked, CP with a low DS. A newer method based on reaction of cellulose with molten urea—H PO is claimed to give water soluble CP (39). The action of H PO and P2 5 cellulose in an alcohol diluent gives a stable, water-soluble CP with a high DS (>5% P) (40). These esters are dame resistant and have viscosities up to 6000 mPa-s(=cP) in 5 wt % solution. Cellulose dissolved in mixtures of DMF—N2O4 can be treated with PCl to give cellulose phosphite [37264-91-8] (41) containing 11.5% P and only 0.8% Cl. Cellulose phosphinate [67357-37-5] and cellulose phosphonate [37264-91 -8] h.a.ve been prepared (42). 

Cyclization onto a heterocyclic ring also readily occurs, as when the 2-substituted pyridine (566) was treated with triethyl phosphite. In this case the pyrrolopyrazole (567) was obtained (79JOC622),... 

This method involves the direct polycondensation of aromatic diamines with aromatic diacids in the presence of an aryl phosphite (triphenyl phosphite) and an organic base like pyridine.7,9 70 71 The addition of salts improves die solubility of the polymer and, with this, the maximum attainable molecular weight.71 The concentrations are, however, lower than by the dichloride method. 

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. ... 

Sulfonic esters are most frequently prepared by treatment of the corresponding halides with alcohols in the presence of a base. The method is much used for the conversion of alcohols to tosylates, brosylates, and similar sulfonic esters. Both R and R may be alkyl or aryl. The base is often pyridine, which functions as a nucleophilic catalyst, as in the similar alcoholysis of carboxylic acyl halides (10-21). Primary alcohols react the most rapidly, and it is often possible to sulfonate selectively a primary OH group in a molecule that also contains secondary or tertiary OH groups. The reaction with sulfonamides has been much less frequently used and is limited to N,N-disubstituted sulfonamides that is, R" may not be hydrogen. However, within these limits it is a useful reaction. The nucleophile in this case is actually R 0 . However, R" may be hydrogen (as well as alkyl) if the nucleophile is a phenol, so that the product is RS020Ar. Acidic catalysts are used in this case. Sulfonic acids have been converted directly to sulfonates by treatment with triethyl or trimethyl orthoformate HC(OR)3, without catalyst or solvent and with a trialkyl phosphite P(OR)3. ... 

Salts of dithiocarbamic acid can be prepared by the addition of primary or secondary amines to carbon disulfide. This reaction is similar to 16-9. Hydrogen sulfide can be eliminated from the product, directly or indirectly, to give isothiocyanates (RNCS). Isothiocyanates can be obtained directly by the reaction of primary amines and CS2 in pyridine in the presence of DCC. ° In the presence of diphenyl phosphite and pyridine, primary amines add to CO2 and to CS2 to give, respectively, symmetrically substituted ureas and thioureas ... 

The rigid, planar pyridine analog 111 was isolated in low yield by first hydrolyzing the known (67) pyridine diethyl phosphonate 109 to the corresponding free acid 110 followed by permanganate oxidation (2). An alternative synthesis of 111 has recently been reported (68). Alkylation of pyridine-2-carboxylate -oxide with dimethylsulfate and subsequent reaction with the sodium salt of diethyl phosphite gave the triester 112, which was readily converted to 111. 

The pyridine ligand in some alkenyl cobalt(III) DMG complexes may be replaced by methyl or ethyl phosphite by addition of the phosphite to a solution of the (DMG)2 complex in ethanol. In a similar manner aniline may be displaced by (CH30)3P from [CH2=CHCo(DMG)2C6HjNH2] (129). 

Schrader prepared the ester (38) in 60% yield by reaction of sodium p-nitrophenate with diethyl chlorophosphate, using xylene as solvent for the reaction. He made it, but in lower yields, from p-nitrophenol and diethyl chlorophosphate, using, respectively, pyridine and sodium cyanide as acceptors for hydrogen chloride. Schrader also prepared it in 96% yield by nitrating diethyl phenyl phosphate at 0° C. or below. Under the conditions he used, Schrader claims that the nitro group is directed to the para position. No yield is given for the diethyl phenyl phosphate, which he presumably made from sodium phenate and diethyl chlorophosphate. Diethyl chlorophosphate may be prepared in high yield (30) from diethyl phosphite and chlorine. 

The broad use of A -carbonyldiimidazole (CDI) for the synthesis of amide and peptide linkages became a routine method only in the early sixties. JV-Protected amino acids were treated at room temperature with an equimolar amount of CDI to give imidazolides. Anhydrous tetrahydrofuran, dimethoxyethane, dichloromethane, pyridine, dimethylfor-mamide, and diethyl phosphite were utilized as solvents. In the second step the esters of amino acids, their hydrochlorides, or sodium salts were added to yield the peptide after several minutes or hours of reaction time. 

Nitrophenyl 2, 3 -0,0-cyclic phosphites 18a-d were formed rapidly and cleanly as two diasteroisomers in the reaction of 5 -0-protected ribonucleosides 16a-d with tris(4-nitrophenyl) phosphite (17) in the presence of pyridine [reaction time less than 3 min at room temperature in DMF/pyridine (9 1 v/v) solution (monitored by 31P-NMR )]. Their sulfhydrolysis, which is also very rapid using an excess of hydrogen sulfide at room temperature, gave cyclic //-phosphonothioatcs 19a-d (Scheme 7) [22], In this reaction, the corresponding 2, 3 -0,0-cyclic... 

Preparation of diethyl pyridine-2-phosphonate — Reaction of an N-methoxy pyridinium salt with a dialkyl phosphite salt... 

To a stirred suspension of N-(2,6-dimethyl-4-oxopyridin-l-yl)pyridin-ium tetrafluoborate (0.58 g, 2 mmol) in dry acetonitrile (20 ml) under nitrogen was added trimethyl phosphite (0.25 g, 2 mmol), followed by finely divided sodium iodide (0.30 g, 2 mmol). After 1 h at 25°C, the solvent was removed under reduced pressure, and water (20 ml) was added. The mixture was extracted with methylene chloride (3 x 15 ml), and the extracts were dried over magnesium sulfate, filtered, and evaporated under reduced pressure. The residue was dissolved in ethyl acetate (40 ml), heated at reflux for 4 h, evaporated under reduced pressure, and eluted on an alumina column (grade 1, neutral) with chloroform to yield pure dimethyl pyridin-4-ylphosphonate (0.36 g, 96%) of melting point (mp) 139 to 140°C. 

Butyllithium (23% in hexane) (63 ml, 0.15 mol) was added dropwise to diethyl phosphite (25 g, 0.18 mol) at -20 to -30°C over a period of 2 h. To the resulting mixture was added A/-methoxy pyridinium meth-osulfate in dimethyl phosphite (40 ml) over a period of 1 h at -15°C. The reaction mixture was stirred at room temperature overnight, and water (100 ml) was then added. The mixture was extracted with chloroform (3 x 75 ml), and the combined organic extracts were separated into neutral and basic fractions by extraction (4 N HC1), bas-ification, and reextraction with chloroform. The basic portion was distilled yielding diethyl pyridine-2-phosphonate (22.9 g, 67%) of boiling point (bp) 105-112°C/0.08 torr. 

A general summary of the chemistry of H4Os4(CO)12 is given in Scheme 10 (159, 166). Substitution reactions with phosphine, phosphites, or pyridine have been observed. An addition reaction occurs with I2 to yield the anionic species [H3Os4(CO)12I] The X-ray structure of this anion has established that the iodide is bridging between two metal centers, to yield an Os4 "butterfly configuration in which one of the metal- metal bonds of the initial Os4 tetrahedron has been broken (Os-Os = 3.817 A) (Fig. 38). Interestingly, if the two Os-1... 

As regards methods of synthesis, one of our early attempts consisted in preparing the trialkyl phosphite, (-RO)3P, by the action of phosphorus trichloride on an alcohol in the presence of a tertiary base such as pyridine or dimethylaniline ... 

Triphenyl phosphite can be prepared by the gradual addition of phosphorus trichloride to a mixture of phenol and pyridine.6 It is claimed that magnesium chloride can be used in place of pyridine.7... 

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