Aluminium oxide phosgene

The conversion of aluminium(III) oxide into aluminium(III) chloride is a reaction of increasing current interest, and a recent review [209] has discussed the reasons for this in some detail. Indeed, the reaction between aluminium(III) oxides and phosgene is one of the most studied inorganic reactions of phosgene. It was first observed by Chauvenet in 1911, who reported that reaction occurred at 400 C [360] ... 

Although bulk silicon(IV) oxide is not chlorinated by phosgene, it does slowly chlorinate the surface [866]. This phenomenon has been used to chlorinate the surfaces of chrysotile asbestos and nonexpanded vermiculite for grafting to polystyrene for use as a filler for polymers and elastomers [1383,1384]. Moreover, in the presence of aluminium(III) chloride, phosgene will convert silica gel into silicon(IV) chloride at between 400 and 700 C [208a,208b]. 

The reaction of phosgene with spent platinum-containing or palladium-containing catalysts on aluminium(IIl) oxide, silicon(IV) oxide, or carbon supports at 140-450 C has been used as part of a recovery process [20,231,1864a,1864c], and car exhaust oxidation catalysts can be reactivated by heating in phosgene at 260 "C [1251],... 

Early attempts by Besson to prepare COBr by the reaction between CO and Br, by oxidation of CHBr3 or CCl Br with ozone, and by treating phosgene with aluminium(III) bromide were unsuccessful [184], but COBr, was claimed to be formed in the reaction... 

Industrial processes for recycling triphenylphosphine oxide have been developed by the French company SNPE and by BASF. The crude triphenylphosphine oxide is purified at around 300°C by vacuum distillation and reacted with phosgene to give 57. The two processes differ in the subsequent reduction step. In the SNPE process, a chloroform adduct of the intermediate 57 is cleaved by hydrogenolysis at 190°C and 100 bar [53]. Use must be found for the hydrogen chloride that is produced in large amounts in this process. In the BASF process, 57 in chlorobenzene is reduced at 130°C with aluminium (Scheme 15) [56]. Triphenylphosphine (54) is isolated by hydrolysis and distillation of the organic phase. 

A-Acylimidazoles are even more easily hydrolysed than A-acylpyrroles, moist air is sufficient. The ready susceptibility to nucleophilic attack at carbonyl carbon has been capitalised upon commercially available I,r-carbonyldiimida-zole (CDI), prepared from imidazole and phosgene, can be used as a safe phosgene-equivalent, i.e. a synthon for 0=C, and also in the activation of acids for formation of amides and esters via the A-acylimidazole. In another application, A-acylimidazoles react with lithium aluminium hydride at O C to give aldehydes, providing a route from the acid oxidation level. 

One of the serious drawbacks of the Wittig reaction is the unavoidable production of triphenylphosphane oxide in stoichiometric quantities. Whilst its direct reduction with boron, aluminium or silicon hydrides would be possible, these reagents are too expensive for a viable process. In fact, distilled triphenylphosphane oxide is reacted with phosgene, generated in situ, to give the corresponding dichloride, which is then reduced with metals, like aluminium. [55]... 

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