Phosphites cyclic

Two fluorines attached to phosphorus instead of the perfluoropinacolyl moiety would cause rapid decomposition. These findings prompted us to try the synthesis of phosphites, cyclic and bicy-clic phosphoranes by a step by step procedure using dilithium perfluoropinacolate J and phosphorus halogenides as starting materials ... 

Sodium hydroxide I chiral quaternary ammonium salts triethyl phosphite Cyclic a-hydroxyketones from ketones Asym. autoxidation under phase transfer catalysis... 

Phosphites, such as triisopropyl and triphenyl phosphite, are weaker electron donors than the corresponding phosphines, but they are used in some reactions because of their greater rr-accepting ability. The cyclic phosphite trimethylol-propane phosphite (TMPP) or 4-ethyl-2,6,7-trioxa-l-phosphabicyclo[2.2.2]oc-tane (8), which has a small cone angle and small steric hindrance, shows high catalytic activity in some reactions It is not commercially available, but can be prepared easily[27]. 

In addition to alcohols, some other nucleophiles such as amines and carbon nucleophiles can be used to trap the acylpalladium intermediates. The o-viny-lidene-/j-lactam 30 is prepared by the carbonylation of the 4-benzylamino-2-alkynyl methyl carbonate derivative 29[16]. The reaction proceeds using TMPP, a cyclic phosphite, as a ligand. When the amino group is protected as the p-toluenesulfonamide, the reaction proceeds in the presence of potassium carbonate, and the f>-alkynyl-/J-lactam 31 is obtained by the isomerization of the allenyl (vinylidene) group to the less strained alkyne. 

Ironically, the reactor was used to produce Antiblaze 19, a flame retardant used in textiles and polyurethane foam. Antiblaze 19 is a cyclic phosphorate ester produced from a mixture of trimethyl phosphite, dimethyl methylphosphonate (DMMP), and trimethyl phosphate (TMOP). The final product is not considered flammable, but trimethyl phosphite is moisture sensitive and flammable, with a flash point of about 27 C. 

Similar reactions between diketopiperazine and either trialkyl phosphites or alkyl phosphinates produced the related cyclic analogs 17 and 18 (24). 

Examples of cyclic aliphatic or aryl phosphonate triesters, such as 36 or 37 have also been prepared by this HHT method from their cyclic phosphite precursors (2). 

When excess amounts of the HHT of phenyl glycinate 42 were used with diphenyl phosphite, the preferred product was the novel cyclic derivative 45 (2). Presumably, ring-opening of the HHT produced intermediate 43 first, which lost an equivalent of glycinate formaldimine to give 44. The proximity of the activated phenyl carboxylate ester to the N-H in 44 presumably promoted intramolecular cyclization to 45 with loss of phenol (2). 

Various cyclic phosphonate esters 36 and 37 have been described previously as products from the HHT reaction of 25 with the appropriate cyclic phosphite. A complementary method has also been developed from the V-protected phosphonyl chloride 84, which was readily prepared from the corresponding phosphonic acid 83. Subsequent reaction of 84 with the appropriate diol produced the cyclic phosphonate esters 85 (63). Higher homologs of 85 have also been prepared from the analogous propane or butane diols. 

Finally, new tricyclic hexacoordinated phosphoranes with internal P-N coordination were synthesized by Swamy and coworkers by oxidative addition of cyclic phosphite precursors with quinones or with a combination of diols and (z-Pr)2NCl [57, 58]. Various ring sizes from five to eight membered were obtained showing the generality of the approach. A selection of compounds (47a-47e) is presented in Fig. 8. 

X-ray crystallographic analyses of the structures show that the P-S bond distance vary over one-half of an Angstrom (2.36-2.88 A). The derivatives were generated using procedures similar to those utilized to form pentaoxyphosphoranes with P-N bonds, that is (i) the oxidation of sulfur containing cyclic chlorophosphines with a quinone or (ii) treatment of phosphites with the sulfur-containing diol in presence of N-chlorodiisopropylamine. Two typical examples of these synthetic protocols are shown in Scheme 10. 

A. Nucleophilic Reactions.—(/) Attack on Saturated Carbon. The Arbusov reaction has been used to prepare organosilicon-substituted phosphonates (1) and phosphorylated ethers (2a) and sulphides (2b). Bromo- and chloro-derivatives of the cyclic phosphite (3) do not react with ethyl halides... 

B. Electrophilic Reactions.—Transesterification followed by rearrangement is a common route from simple phosphites to more complex phos-phonates. This has now been applied to the preparation of cyclic phos-phonates (85). Both phosphites (86) and phosphoranes (87) containing phosphorus-hydrogen bonds are obtained from the cyclic biphosphite (88) and butanol. ... 

D. Cyclic Esters of Phosphorous Acid.—There has been some controversy about the stable stereochemistry at phosphorus in cyclic phosphites and phosphonites this now appears to be resolved by agreement in a series of papers. The stereochemistry of 2-alkoxy-4-methyl-l,3,2-dioxaphosphorins... 

Russian workers have studied secondary cyclic phosphites (113) and (114). Unfortunately, the situation is far from clear since m-(115) iso-nierizes to trans- 16) on standing, " but (117) is suggested to be thermodynamically more stable than (118). This apparent contradiction could be explained by either an incorrect assignment of isomers or a 1,3-interaction of the 4-methyl group in (114). 

On-line SFE-pSFC-FTIR was used to identify extractable components (additives and monomers) from a variety of nylons [392]. SFE-SFC-FID with 100% C02 and methanol-modified scC02 were used to quantitate the amount of residual caprolactam in a PA6/PA6.6 copolymer. Similarly, the more permeable PS showed various additives (Irganox 1076, phosphite AO, stearic acid - ex Zn-stearate - and mineral oil as a melt flow controller) and low-MW linear and cyclic oligomers in relatively mild SCF extraction conditions [392]. Also, antioxidants in PE have been analysed by means of coupling of SFE-SFC with IR detection [121]. Yang [393] has described SFE-SFC-FTIR for the analysis of polar compounds deposited on polymeric matrices, whereas Ikushima et al. [394] monitored the extraction of higher fatty acid esters. Despite the expectations, SFE-SFC-FTIR hyphenation in on-line additive analysis of polymers has not found widespread industrial use. While applications of SFC-FTIR and SFC-MS to the analysis of additives in polymeric matrices are not abundant, these techniques find wide application in the analysis of food and natural product components [395]. 

In a study of the reactions oi acyclic o-methoxyphenyl-phosphinites (45a), phosphonites (45b) and phosphites (45c) with halogens,the intermediate halogenophosphonium salts (46) are stabilised either by ligand exchange with starting material (not shown) or by elimination of methyl halides to form cyclic phosphoranes ( 47 ) 3 7. ... 

An extensive paper by Burgada et l. reports the reactions of cyclic phosphites (75 ab) and cyclic phosphoramidites (76 ab) with trans-1,2-dibenzoylethene, methyl fumarate, benzalacetone (PhCH=CH COMe), methyl-4-keto-pent-2-enoate (MeCO.CH=CH.COgMe) and benzalacetophenone (PhCH=CHCOPh)95. These reactions lead to... 

MeO), cyclic phosphonates (50). The formation of (50) is strong evidence for the involvement of carbenes (51). Diethyl alkylphospho-nites (52) deoxygenate aromatic aldehydes upon heating only small amounts of the a-ethoxybenzylphosphinate (53), which is analogous to products obtained from trialkyl phosphites and aromatic aldehydes, are formed. 

A convenient synthesis of uridine 2, 3 -cyclic phosphite 15 (as a 3 4 mixture of diasteroisomers because of the chirality at phosphorus) was based on the reaction of the suitably protected uridine derivative 14 with ethyl dichlorophosphite carried out in the presence of triethylamine and anhydrous ethanol (Scheme 6) [21]. After adding ethanol into the reaction medium, an efficient chromatographic separation of the crude reaction product was achieved on silica gel with diethyl ether giving analytically pure phosphite 15 in 75% yield. It is interesting to note that without adding ethanol, 15 is very unstable. 

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... 

In this context, it is interesting to note that the first synthesis of 2, 3 -0,0-cyclic phosphorothioate 22a was reported by Eckstein in 1968 [25], He also isolated pure Rp diastereomer by fractional crystallization of the triethylammonium salts [26] and used it as reference to determine the absolute configurations of the other phosphorothioate analogues [27], 2, 3 -0,0-Cyclic H-phosphonate 20a was used as a key substrate for the synthesis of uridine 2, 3 -0,0-cyclic boranophosphate 27. Silylation of H-phosphate 20a gave the phosphite triester 25 (two diastereomers). Its boronation, with simultaneous removal of the trimethylsilyl group, was achieved by its reaction with borane-A.A-diisopropylethylamine complex (DIPEA-BH3). 

Mechanism 3 involves NiOH in at least three reactions, and Ni(OH)2 as the active Ni reactant in solution. Since increasing the concentration of the complex-ant(s) in solution will reduce the concentration of both unhydrolyzed and hydrolyzed metal ions, arguments of complexation cannot be readily employed to either support or discount this mechanism. However, it has been this author s experience in formulating electroless Co-P solutions with various complexants for Co2+ that improper complexation which results in even a faint precipitate of hydrolyzed cobalt ions yields an inactive electroless Co-P solution. Furthermore, anodic oxidation of hypo-phosphite at Ni anodes does not proceed at a significant rate under conditions where the surface is most probably covered with a passive film of nickel oxide [48], e.g. NiO.H20, which would be expected to oxidize the reducing agent via a cyclic redox mechanism. 

The photolysis of carboxylic acids and derivatives as lactones, esters and anhydrides can yield decarboxylated products 253>. This reaction has been utilized in the synthesis of a-lactones from cyclic diacyl peroxides 254) (2.34) and in the synthesis of [2,2]paracyclophane by bis-decarboxylation of a lactone precursor (2.35) 255). This latter product was also obtained by photoinduced desulfurization of the analogous cyclic sulfide in the presence of triethyl phosphite 256). 

Among transition metal complexes used as catalysts for reactions of the above-mentioned types b and c, the most versatile are nickel complexes. The characteristic reactions of butadiene catalyzed by nickel complexes are cyclizations. Formations of 1,5-cyclooctadiene (COD) (1) and 1,5,9-cyclododecatriene (CDT) (2) are typical reactions (2-9). In addition, other cyclic compounds (3-6) shown below are formed by nickel catalysts. Considerable selectivity to form one of these cyclic oligomers as a main product by modification of the catalytic species with different phosphine or phosphite as ligands has been observed (3, 4). 

Reaction of the sodium salt of a cyclic phosphite diester with a bis-benzylic halide... 

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

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