369 dichlorophosphates

O The alcohol hydroxyl group reacts with POCI3 to form a dichlorophosphate intermediate. 

E2 elimination then occurs by the usual one-step mechanism as the amine base pyridine abstracts a proton from the neighboring carbon at the same time that the dichlorophosphate group is leaving. 

The 4-chloropyrimidin-2-yl dichlorophosphate ester has been isolated in 58% yield as an intermediate in the chlorination of 6-(trifluoromethyl)uracil with POClj followed by PC15 (83JHC219). The enhanced stability of this compound was believed to be due, in part, to electron withdrawal by the CF3 group. Tri-n-propylamine was found to be the most effective in a comparison of the influence of bases on chlorination with POCl3 (87JHC1243). 

The submitters, working on a kilogram scale without purification of reagent or solvent and with no precaution against moisture, obtained 6,7-dimethoxy-l-methyl-3,4-dihydroisoquinoline hydrochloride,2 m.p. 202-203°, instead of the dichlorophosphate at this stage. The checkers obtained this hydrochloride by either treating the free base with... 

Last, but not least, there is to be mentioned, that in some cases a direct transformation of dichlorophosphates (see section 3.4.) into difluorophosphates by fluorination with elementary fluorine (In(P02p2)3, F (P02F2)3 40)) or with arsenic trifluoride at elevated temperature is possible 41). ... 

The most intensely investigated of all halophosphates are certainly the dichlorophosphates, about which extensive crystallographic and spectroscopic data exist. This might be brought into connection with the fact, that for the preparation of the dichlorophosphates there is an especially rich variety of methods for synthesis at hand. On the... 

Other hand the dichlorophosphate groups represent interesting objects of study as far as their different ways of coordination are concerned (I—V), going from the monofunc-tional dichlorophosphate group (I) to the ion (II) and the trifunctional structural element (V) ... 

Table 2 gives a view of the inorganic dichlorophosphates, known at present, and the structural types of their dichlorophosphate groups. 

The most numerous structural types (IVa) and (IVb) of the dichlorophosphate group are related in so far as there is the same kind of linkage by the bifunctional... 

On the other hand the dichlorophosphates of bivalent metals, such as Mg, Mn, ... 

The oldest of the numerous syntheses of dichlorophosphates dates back to 1911 (S7) it makes use of the reaction of metal oxides (MgO, CaO, MnO) with POCI3 in presence of solvatating organic molecules (e.g. ethyl acetate = E). This reaction can be understood by the access of moisture from the air (26) as well as by the simultaneous formation of metal chloride (27) ... 

However, the nature of these compounds could not be determined until in 1963 Danielsen et al. made a crystal structure analysis of the manganese compound (77). Later on these dichlorophosphates, in analogy to reaction (26), were prepared from dichlorophosphoric anhydride too ... 

Even oxyhalides such as SnOClg, XiOCl2 etc. react readily in boiling phosphoryl chloride, forming dichlorophosphates (72,83,84,85) ... 

The volatility of trifluoroacetyl chloride may explain the smooth reaction when preparing neodymium(tris)dichlorophosphate, which is of some interest for dye-lasers, from trifluoroacetate and POCI3 (79) ... 

Of some importance for the preparation of various dichlorophosphates are cleaving reactions of the P-O-P bridge in P2O3CI4, which quite often reacts completely with some organometallic oxides (36) 82) or suitably substituted ethers (37) 63) ... 

Also, the reaction of metal chlorides with anhydrous dichlorophosphoric acid is convenient for the preparation of some dichlorophosphates, as is shown by the following examples 88, 64, 74, 76) ... 

Last, but not least it should be mentioned, that the acidity of dichlorophosphoric acid is sufficient, to dissolve some metals (Fe, Co, Ni) under formation of hydrogen and dichlorophosphates 78) ... 

Up to know crystal structure analyses have been made with difluorophosphates, monofluorophosphates and dichlorophosphates only. Table 3 gives the bond lengths and bond angles in these three halophosphates. 

Analogous spectroscopic behaviour, as pointed out for the dichlorophosphates for example, can be expected in the case of the difluorophosphates and the dihalophos-phates with two different halogen atoms. 

No details are given for scheme A. Presumably one could use the phosphoryl chloride instead of the fluoride. Scheme B, in which ethyl chloride is formed, was run in boiling xylene using equimolar quantities of the reactants. Michaelis (33) has partially described the preparation of starting materials from secondary amines with phosphorus oxychloride and also ethyl dichlorophosphate. Schrader (38) obtained alkyl and amido fluophosphates by reaction of the corresponding chlorophosphates with sodium fluoride in aqueous or alcoholic solution. 

The activated phosphorus reagents 269 and 270 are conventionally prepared by the reaction of 2(3//)-oxazolone with the corresponding phosphorus chlorides in the presence of triethylamine. The phosphorus chlorides employed include phosphoryl chloride, thiophosphoryl chloride, mono- and dichlorophosphates, and phosphinic chloride (Fig. 5.66). 

Chloroethanol, Ethanol, 2-chloro-, (107-07-3), 65, 150 2-Chloroethyl dichlorophosphate Phosphorodichlor1d1c acid, 2-chloroethyl... 

Treatment with dimethyl sulfoxide in the presence of phenyl dichlorophosphate or phosphoryl chloride converts ( + )-a-pinene (39) to (6/ ,4.S)-4-isopropenyl-l-methyl-6-chlorocyclohexene (51) in virtually quantitative yield, presumably also via the cyclobutylmethyl to pent-l-enyl cation rearrangement.164 Similarly, / -pinene (45) is converted to 4-isopropenyl-l-chloromethylcyclohexene (52), also in quantitative yield.164... 

---