Dialkyl phosphites cyclic

Asymmetric addition of phosphorus compounds to C-N double bonds has been widely studied and mainly concerns the synthesis of chiral a-aminophosphonic acids (for reviews on the synthesis of aminophosphonic acids, see refs 36, 37 and 67). For this purpose, the following types of organic nitrogen compounds have been used aldimines and cyclic imines, nitrones, ureidoimino derivatives and imidothioloesters. A separate example is the addition of dialkyl phosphites to hydrazones, which was used for the synthesis of phosphonosugars. 

Glycosyl phosphites were introduced by Schmidt [451-453], Wong [454-457] and Watanabe [458,459], A variety of dialkyl and cyclic phosphites has proved suitable for the reaction [459,460], In fact, diethyl and dibenzyl phosphites are the most frequently used. Glycosyl phosphites react with alcohols at low temperamres in the presence of catalytic amounts of Lewis acid promoters such as TMSOTf, BF3-Et20 and Sn(OTf)2, thus creating glycosides. Phosphites are also activated by other promoters, which are summarized in Table 4.9. 

A convenient synthesis of cyclic P-ketophosphonates has been reported from sodium dialkyl phosphites and oc-nitroepoxides. The phosphite anions attack regiospecifically the carbon P to nitro group with epoxide ring opening and elimination of sodium nitrite. All the cyclic dialkyl P-ketophosphonates are isolated in good yields (56-96%, Scheme 7.50). 

Kim, D.Y, and Kong, M., A new synthesis of cyclic P-keto phosphonates from a-nitro epoxides and a dialkyl phosphite, J. Chem. Soc., Perkin Trans. 1, 3359, 1994. 

Unquestionably, one of the most attractive synthetic methods for the preparation of dialkyl 2-(alkoxycarbonyl)ethylphosphonates involves the conjugate addition of a dialkyl phosphite to the carbon-carbon double bond of a,p-unsaturated carboxylates (Pudovik reaction, Scheme 8.44). In the presence of EtONa, diethyl phosphite reacts vigorously with acrylate in EtOH to give the Michael addition product in 84% yield. The reaction is applied with success to the synthesis of dialkyl 2-(alkoxycarbonyl)ethylphosphonates bearing a large variety of acyclic (symmetric - or disymmetric 30 or cyclic (symmetric or disynunetric ) substituents at phosphorus. 

The first efficient enantioselective synthetic route to cyclic a-amino phosphonates, namely the pharmaceutically interesting heterocyclic phosphonates of type 1 [63,64],by an asymmetric addition reaction of dialkyl phosphites to heterocyclic imines was recently developed by Shibasaki et al. (Scheme 23) [ 10,77]. 

Rare examples of normal Michaelis-Becker reactions which involve co-chloroalkanal diethyl acetals are to be found, and although the formation of dialkyl acylphosphonates from sodium dialkyl phosphites and, for example, benzoyl chloride, is to be observed at -85 °C, the system is further complicated, even at -10 °C, by further addition steps followed by rearrangements which would seem to render the process of little value for the synthesis of oxoalkyl phosphonic esters On the other hand, in a more detailed and systematic study of reactions between sodium dialkyl phosphites, (RO)2PONa(R = Et or Bu), and the ketones R CO(CH2) Cl, Sturtz and others have observed the formation of epoxides when n = 1 and (1-hydroxy alk-2-enyl)phosphonic diesters when n = 2(R = Me or Pr ), according to the displacement in 532, and of derivatives of tetrahydrofuran or tetrahy-dropyran, according to 533 n = 3 or 4) when R = Et, the formation of the cyclic ethers was accompanied by low yields of the expected (oxoalkyl)phosphonic diester, but otherwise the latter were isolated as a single product only for R = Me, n = 5, and R = Et or Pr when n = 2. 

Sugar aldehydes give phosphonates on treatment with dialkyl phosphites which have been used to prepare cyclic hydroxylamine... 

Cyclic a-amino-a,p-ethylenephosphonic acid esters from iminoester salts and dialkyl phosphites... 

In the first approach, small molecule cyclic (Scheme 22) and high polymeric (Scheme 23) phosphazenes bearing bromomethylene - phenoxy side groups are treated with a sodium dialkyl phosphite, as shown in Scheme 22. 

It was possible to carry out hydrophosphorylation of non-activated alkenes only with cyclic five-membered P-H substrate using cis-PdMcaLa as catalyst precursor (Scheme 8.15) [77]. Neither six-membered analogs of the substrate, nor non-cyclic dialkyl phosphites were active in this catalytic addition reaction. 

Trialkyl phosphites undergo reaction with molecular halogen via a mechanism reminiscent of the Michaelis-Arbuzov reaction to form the dialkyl phosphorochloridate in good yield (Equation 4.4).7 With cyclic esters, the halogen performing the displacement reaction at carbon remains attached within the molecule. 

The scope of the transphosphoranylation reaction is enlarged by the availability of cyclic oxyphosphoranes (99) from the reaction of phosphites with certain dialkyl peroxides.14 Several cyclic and acyclic... 

The first example of the asymmetric synthesis of P-chiral trialkyl phosphates (12) via trialkyl phosphite, in which the keystone is dynamic kinetic resolution in the condensation of a dialkyl phosphorochloridite (13) and an alcohol by the catalytic assistance of a chiral amine has been reported (Figure 2)." 2,4-Dinitrophenol (DNP) was employed as an activating reagent with ben-zyloxy-bis-(diisopropylamino) phosphite to synthesize the cyclic phosphate derivatives (14) from a series of alkane diols HO-(CH2)n-OH (n=2-6). Included was a cyclic phosphate derivative of carbohydrate (15). The mechanism of activation by 2,4-DNP and cyclization was also described (Figure 3). ... 

Dawson and Burger first demonstrated that the Michaelis-Arbuzov reaction of chloroacetonitrile and triethyl phosphite furnishes diethyl cyanomethylphosphonate. In its most general form, it involves the addition of triethyl phosphite to chloroacetonitrile at 150-170°C to give diethyl cyanomethylphosphonate in up to 80% yields (Scheme 6.2). ° This procedure has been developed on an industrial scale The use of bromo- or iodoacetonitrile (X = Br, I, Scheme 6.2) was also reported. The reaction may be used to prepare any dialkyl cyanomethylphosphonate, and a variety of trialkyl phosphites have produced the corresponding phosphonates in reasonable to good yields (29-90%, Scheme 6.2). " Cyclic phosphites, 4,5-dimethyl-2-methoxy-l,3,2-dioxaphos-pholane (meso and racemic) and 5,5-dimethyl-2-methoxy-l,3,2-dioxaphosphorinane, react with chloroacetonitrile to produce 5- and 6-membered cyclic phosphonates in 50% and 72% yields, respectively. ... 

It has been shown recently that 3-oxocycloaIkylphosphonates can be prepared by photochemical phosphonosilylation of cyclic a,P-unsaturated ketones. Thus, irradiation of a mixture of dialkyl trimetylsilyl phosphite and cyclic a,P-unsaturated ketones in MeCN provides essentially conjugate... 

The estimation of phosphorus by g.l.c. has been reviewed. Cyclic phosphites, phosphonates, and phosphates have been analysed by g.l.c. The zinc, gold, and cadmium chelates of dialkyl dithiophosphinates (235 ... 

The thermally initiated isomerization of dialkyl alk-2-enyl phosphites leads to phos-phonic diesters (reaction 52) and is also to be found in cyclic systems when, for instance, the l,3,2-dioxaphosph(III)orin 386 gives the l,2-oxaphosph(V)olene 387 °. 

The use of oxirane together with Na2HP03 to prepare (2-hydroxyethyl)phosphonic acid as its disodium salt is of historical interest. Other poorly exploited, yet interesting and potentially valuable, reactions include the combination of a trialkyl phosphite and dialkyl chlorophosphate with an oxirane to yield O-phosphorylated derivatives of (2-hydrox-yalkyl)phosphonic diesters (reaction 10)" and, following the initial reaction of an a,j8-unsaturated ketone with a phosphorus(III) triester to give the cyclic phosphorane 272, the subsequent further reaction of the latter with an aldehyde followed by hydrolysis (reaction 11)" Dialkyl acetyl phosphites are reported to react with oxirane through anionic intermediate species with the formation, albeit in low yields, of dialkyl (2-acetyloxyethyl)phos-phonates hydrolysable with concentrated HCl, to give (2-hydroxyethyl)phosphonic acid ... 

Phosphoric acid, triphenyl ester. See Triphenyl phosphate Phosphoric acid, tris (2-ethylhexyl) ester. See Trioctyl phosphate Phosphoric acid, tris (methylphenyl) ester Phosphoric acid, tritolyl ester. See Tricresyl phosphate Phosphoric acid, zinc salt (2 3). See Zinc phosphate Phosphorodithioic acid, mixed 0,0-bis (iso-butyl and pentyl) esters, zinc salt. See Zinc dialkyl dithiophosphate Phosphorous acid, cyclic neopentanetetrayl bis (2,4-di-t-butylphenyl) ester. See Bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite Phosphorous acid, triisooctyl ester. See Triisooctyl phosphite Phosphorous acid triphenyl ester. See Triphenyl phosphite... 

Dialkyl esters of 3,3 -thiodipropionic acid (52), cyclic phosphonites such as neopentylphenyl phosphite, derivatives of phosphaphenathrene-lO-oxide (53), secondary aromatic amines such as diphenylamine (54), and epoxidized soybean oils (55) are effective stabilizers for preventing discoloration of cellulose esters during thermal processing. 

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