Antimony complexes rearrangement

Antimony pentachloride complexes of A-oxides of pyridine, quinoline and isoquinoline rearrange on heating to give the corresponding pyrid-2-one, carbostyril or isocarbostyril, e.g. Scheme 118 (81T1871). 

Aluminum trichloride is the most commonly used catalyst, although aluminum tribromide is more efficient.1 For the rearrangement of l-broino-2-chloro-1,L2-lrifluoroethane (3) to 2-bromo-2-chloro-l,l,l-trifhioroethane (4). none of the following Lewis acids are effective iron(III) chloride. iron(III) bromide, antimony(III) chloride, antimony(V) chloride. tin(IV) chloride, titanium(IV) chloride, zinc(II) chloride, and boron trifluoride-diethyl ether complex.1" ... 

The reactions of perfluoroisobutene with sodium salts of malonic esters are difficult to control, owing to rearrangement and base catalysed cyclization, but when the complex BFs NEts is used as HF acceptor, condensation is readily controlled (see Scheme 15 and p. 99) and yields of up to 50% of allene (39) obtained. Antimony pentaliuoride catalyses the electrophilic addition of acid fluorides to 1,1-difluoro- and trifluoro-ethylene. Propiophenones, PhCO CHX-CFs (X = H or F), are obtained from benzoyl fluoride, but with acetyl fluoride, further condensation occurs, and trifluoroethylene yields the jS-diketone, CF3-CHF-CO-CH2Ac. ... 

Antimony pentachloride, unlike other Lewis acids and proton adds, reacts with various azoxybenzenes to give 1 1 complexes (26) in high yield. Thermolysis of (26) in inert solvents gives o-hydroxyazobenzenes via a selective Wallach rearrangement (Scheme 40). 

---