Phosphorus aryl groups

Chloroquinazoline can be isolated, at best in 40% yield, by boiling 2-hydroxyquinazoline with phosphorus pentachloride in phosphorus oxychloride for 45 min, and attempts to improve this yield have proved fruitless. The yields are much higher when an aryl group is in position 4 w hich suggests an attack of the 3,4-double bond in 2-hydroxy- and 2-chloro-quinazolines by the chlorinating agent. 

The reaction affords in variable yields (19-85%) a stabilized phosphonium yhde exhibiting two electron withdrawing substituents on the ylidic carbon a to the phosphorus atom, and requires apparently a dialkylarylphosphine oxide incorporating an overcrowded 2,4,6-trisubstituted aryl group. 

Like the C NMR chemical shifts for the central carbon of heteroallenes. changing the composition of the allene fragment can have as much of an effect (if not more) on the Si chemical shift as does changing a substituent. Switching the carbon at position 3 to a phosphorus (silaphosphaallene 122) moves the " Si chemical shift downheld to 75.7 ppm, which is the most deshiclded " Si shift fora silaallene to date, even though it has two aryl groups on silicon, which should keep the shift uplield. 

The products from the reactions with phosphorus pentachioride vary even with the nature of the aryl group. Thus, the p-chlorophenyl compound gave a product analogous to (6), but it was accompanied by the dimeric phosphazene, [p-ClCeHiNPClsJa. 

Restricted rotation has been observed in tris-o-tolylphosphine sulphide and selenide (39). The spectrum of the selenide shows two methyl environments in the ratio 2 1 at 30 °C but the methyl signals of the sulphide resolved to this pattern only upon cooling the sample. The corresponding oxide and the parent phosphine showed only one methyl environment down to — 60 °C. Y-Ray diffraction of the selenide showed that the methyl group on one aryl group is directly behind the phosphorus atom in the crystal, as shown in (39). 

Combined dipole moment and Kerr effect studies are regularly used by Russian workers for the conformational analysis of phosphorus heterocyc1es.135 230 In a study of the interaction of phenol with phosphoryl groups the Kerr effect was used to evaluate not only the extent of hydrogen bonding but also the influence of changes in polarity and polarisation upon stability constants.231 In a similar study the orientation of the aryl groups of 1,3,5-triazaphosphorines (82) were shown to be less coplanar than biphenyl in the gas phase. 2 3 2... 

A common feature of the solubihty curves, as outlined in Fig. 16, is the exponential increase with the pressure due to the increasing density of CO2. From the solubility measurements [125], it can be concluded that the modification of phosphines by fluorous substituents is not necessarily required to reach sufficient solubilities of the corresponding metal complexes in SCCO2. In particular, alkyl substitution on phosphorus promotes complex solubility. Additional aryl groups, e.g., in lb and 4b, cause a reduced solubility of the corresponding complexes. Moreover, trans-Co2(CO)6 (PC6H5)3 2 (7b) is completely insoluble in SCCO2. 

Sulfonic acids are prone to reduction with iodine [7553-56-2] in the presence of triphenylphosphine [603-35-0] to produce the corresponding iodides. This type of reduction is also facile with alkyl sulfonates (16). Aromatic sulfonic acids may also be reduced electrochemicaUy to give the parent arene. However, sulfonic acids, when reduced with iodine and phosphorus [7723-14-0]y produce thiols (qv). Amination of sulfonates has also been reported, in which the carbon—sulfur bond is cleaved (17). Ortho-lithiation of sulfonic acid lithium salts has proven to be a useful technique for organic syntheses, but has litde commercial importance. Optically active sulfonates have been used in asymmetric syntheses to selectively O-alkylate alcohols and phenols, typically on a laboratory scale. Aromatic sulfonates are cleaved, ie, desulfonated, by uv radiation to give the parent aromatic compound and a coupling product of the aromatic compound, as shown, where Ar represents an aryl group (18). 

The greater electronegativity of Cipso in an aryl group as compared with an alkyl group (or other aryl groups) gives an upfield chemical shift, qualitatively in accordance with the possibility of the formation of dn-pn bonds38. The phosphorus resonances of... 

---