Isomerization phosphites

The rate ratio for substitution of phenoxy groups by methoxide ions in (69) and (70) has been shown to be very solvent dependent. Although a high rate ratio (k(69) k(70) = 1.8x10 ) was found in methylene chloride, the ratio was only 14 in methanol. The authors propose an ion-pair stabilized phosphorane-like structure (71) for the transition state or intermediate in methylene chloride, which has a favourable axial-equatorial placement of the five-membered ring, to account for the high ratio in this solvent, and an in-line Sn2 mechanism to apply in methanol, where ion-pairing is unimportant The different stereochemical expectations (retention in methylene chloride and inversion in methanol) could not be verified because phosphites isomerize under the reaction conditions. 

Carboxylic acids react with butadiene as alkali metal carboxylates. A mixture of isomeric 1- and 3-acetoxyoctadienes (39 and 40) is formed by the reaction of acetic acid[13]. The reaction is very slow in acetic acid alone. It is accelerated by forming acetate by the addition of a base[40]. Addition of an equal amount of triethylamine achieved complete conversion at 80 C after 2 h. AcONa or AcOK also can be used as a base. Trimethylolpropane phosphite (TMPP) completely eliminates the formation of 1,3,7-octatriene, and the acetoxyocta-dienes 39 and 40 are obtained in 81% and 9% yields by using N.N.N M -tetramethyl-l,3-diaminobutane at 50 in a 2 h reaction. These two isomers undergo Pd-catalyzed allylic rearrangement with each other. 

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. 

Bisphosphites such as (7) combine excellent reactivity, straight-chain selectivity, and high resistance to the typical phosphite degradation reactions (29). Further, the corresponding 0x0 catalysts are excellent olefin isomerization catalysts so that high normal-to-branched isomer ratios are obtained even from internal olefins, enabling, in certain instances, the use of inexpensive mixed isomer olefin feedstocks. 

R3P03 RO—P—OR 1 OR triphosphite ester (phosphite) hypothetical phosphorous acid, P(0H)2 stmcture is isomeric with phosphonates... 

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. 

Sulfites. The Hterature concerning dialkyl sulfites is extensive, although less than for sulfates. Reactions involving alkylation are similar to those of sulfates. Sulfites also undergo elimination, transesterification, and isomerization. The last two parallel reactions of phosphites. 

The deoxygeneration of nitroarenes by trivalent phosphorus compounds in the presence of amines is a useful route to 3/f-azepin-2-amines (cf. compounds 32, Section 3.1.1.4.2.2.). Subsequently, it has been shown, by carrying out the reaction in strongly basic solution, that the process can be extended to the synthesis of 1H-. 3H- and 5//-2-benzazepines from nitronaph-thalenes 43 For example, 1-nitronaphthalenes 3 with dimethyl phosphite in the presence of sodium methoxide and a primary or secondary aliphatic amine, yield the dimethyl 5//-2-ben-zazepin-3-yl phosphonates 4 accompanied, in some cases, by the isomeric 3//-2-bcnzazepin-3-yl phosphonates 5. 

Nickel, diiodotris(trimethyl phosphite)-strpeture, 1,45 Nickel, hcxaamminc-rcactions, 1,27 Nickel, hexaaqua-reactions, 1, 204 Nickel, hexafluoro-, 5,186 Nickel, hexakis(A, Ar -dimethylurea)-tetrachloronickelate isomerization, 1,470... 

Isomeric products (75) and (76) are obtained from the reaction of perfluoroacetone with dialkyl phosphites. " The relative proportions of the isomeric mixture depend on the alkyl group in the phosphite and the results are explained in terms of the polarity of the P-H bond and hence its direction of addition to the carbonyl group. Presumably, the balance in these cases is very finely adjusted, although these reactions are possibly more complicated than the results suggest. 

Conformational populations of cyanomethylphosphine oxides (136) have been estimated from dipole moments and indicate a preference for the tra/15-conformation. The moments of the o-, m- and p-chloro- and tolyl-derivatives of triaryl phosphites (137, Y = ) and triaryl phosphates (137 Y = O) indicate that the oxygen atom in the latter series causes the aryl rings to rotate further away from a position in which their planes all meet along the molecular symmetry axis. Conformational studies have also been carried out on the dioxaphosphorinanes. The moments of the isomeric series (138a) and (138b) were in the ranges 3.7—4.2 and 5.4—5.5 D respectively. ... 

G.l.c. studies of tributylphosphine, dialkyl phosphites, and dialkyl alkylphosphonates are reported. Tributyl phosphate in nitric acid can be estimated by g.l.c. if a glass column is used. Tetraethyl pyrophosphate has been directly determined on a nanogram scale by g.l.c., whereas it was found most convenient to first convert the tetra-aryl pyrophosphates by methanolysis to diarylmethyl phosphates. Phosphorochloridates were converted by t-butyl alcohol into t-butyl chloride before analysis. G.l.c. studies of pesticides have been reported and the isomeric thiophosphates (138a) and (138b) have quite different retention times. ... 

P-H oxidative addition followed by alkyne insertion into a Pd-P bond gives the re-gio-isomeric alkenyl hydrides 15 and 16. Protonolysis with diaUcyl phosphite regenerates hydride 17 and gives alkenylphosphonate products 18 and 19. Insertion of alkene 18 into the Pd-H bond of 17 followed by reductive eUmination gives the bis-products, but alkene 19 does not react, presumably for steric reasons. P-Hydride elimination from 16 was invoked to explain formation of trace product 20. 

The allylic acetate 47 can be isomerized to 48 by the palladium catalyst. When Pd(acac)2 and PPh3 were used, 47 was converted at 90°C for 12 hours into a 3.9 1 mixture of 47 and 48. But the ratio remained 17 1 when tris(o-methylphenyl)phosphite (52) was used. 

Bentrude, W.G. and Hargis, J.H., Conformations of six-membered ring phosphorus heterocycles. I. The ring conformations and phosphorus configurations of isomeric six-membered ring phosphites, /. Am. Chem. Soc., 92, 7136, 1970. 

If R=R the reaction appears to be catalytic, as a small quantity of 12 Cl will suffice to convert a considerable quantity of the phosphite into the alkylphosphonate2 (I). As little as 0 01 ml. of methyl iodide will isomerize trimethyl phosphite.3 Methyl iodide can be replaced satisfactorily by dimethyl sulphate. 

Among phosphorus insecticides containing also nitrogen and sulphur we may mention 00 -diethyl-/S-/ -diethylaminoethyl phosphorothiolate (X). It was prepared (i) from diethyl phos-phorochloridate1 and sodium / -diethylaminoethyl mercaptide, (ii) from sodium diethyl phosphite and / -diethylaminoethyl thiocyanate, (iii) by the isomerization of OO -diethyl-O"-/ -diethylaminoethyl phosphorothionate (XI) obtained from / -diethylaminoethoxide and diethyl phosphorochloridothionate. 

Propylene carbonate is a good solvent of the rhodium precursor [Rh(acac) (00)2] and the phosphite ligand BIPHEPHOS and can thus be used as the catalyst phase in the investigation of the isomerizing hydroformylation of trans-4-octene to n-nonanal in a biphasic system [24]. As already mentioned, the reaction products can be extracted with the hydrocarbon dodecane. Instead of an additional extraction after the catalytic reaction, we carried out in-situ extraction experiments, where the products are separated from the catalytic propylene carbonate phase while the reaction is still in progress. Conversion of 96% and selectivity of 72% was achieved under comparably mild conditions (p(CO/H2) = 10 bar, T = 125 °C, 4 h, substrate/Rh = 200 1). 

Isomeric l,3a,4,6a- (220) and l,3a,6,6a- (91) dibenzotetraazapentalenes can be prepared from the thermal decomposition of 2-((9-azidophenyl)-2//-benzotriazole (224) and - o-azidophenyl)-2//-benzotriazole (230), respectively, in high boiling solvents such as 0-dichlorobenzene and decalin. This synthesis was improved upon when it was found that (220) and (91) can be prepared from the reactions of 2-((9-nitrophenyl)-2//-benzotriazole (226) and l-(o-nitrophenyl)-2//-benzotriazole (229), respectively, with triethyl phosphite in refluxing xylene. ... 

---