Reactions of Friedel-Crafts type

Another method is oxidation in situ to thiophosphonic chlorides. 

Phenyl(thiophosphonic) dichloride 149 Benzene (23 g), phosphorus trichloride (124 g), and aluminum chloride (40 g) are heated and stirred together under reflux for 3 h. The product is cooled to 30° and treated with sulfur (10 g), the temperature then rising to 60° and the color darkening. When the exothermic reaction ceases the mixture is heated for a few min at 80°, then the excess of phosphorus trichloride is removed in a vacuum. The residue is poured on ice and twice extracted with light petroleum. The extracts are washed with water and dried over calcium chloride. After removal of the solvent fractionation in a vacuum affords the dichloride (46.7 g, 73.8% calculated on benzene), b.p. 128-130°/12 mm, 95-110°/2-3 mm, 72-75o/0.5 mm, nD20 1.6227. 

The aryldichlorophosphines themselves first became readily accessible when it was found that the aluminum chloride could be precipitated quantitatively from the product by addition of phosphorus oxychloride150 or pyridine.151 Optimum yields are obtained with the ratios hydrocarbon PC13 A1C13 = 0.3 1.2 0.4 with subsequent addition of an amount of phosphorus oxychloride equivalent to the aluminum chloride.152 

Alkylbenzenes react analogously isomer proportions in the products are reported by Baldwin and his co-workers.153 The yield of aryldichlorophosphine decreases rapidly with increasing alkyl substitution of the ring it is already zero with mesitylene. As a variation of the process, the diarylphosphine oxides, together with small amounts of the diarylphosphinic acids, can be obtained by hydrolysis of the insoluble POCl3/AlCl3 complex. 

General procedure for the preparation of diarylphosphine oxides from mesitylene, durene and pentamethylbenzene 154 The hydrocarbon (0.3 mole) is treated with phosphorus trichloride and aluminum chloride as in the preceding prescription. After addition of the phos- 

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Reactions of Friedel-Crafts type. The high-yield condensation of benzene with y-butyrolactone to give a-tetralone accomplishes in one step what can be done by... 

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