Phosphorus oxybromide

The decomposition of the phosphorus oxybromide may also be conducted in a 1-litre three-necked flask charged with 400 g. of finely crushed ice and fitted with a reflux condenser and mechanical stirrer. 

Bromopyridine has been made by direct bromination of pyridine - from N-methyl-2-pyridone with phosphorus penta-bromide and phosphorus oxybromide from 2-aminopyridine by diazotization with amyl nitrite in 20% hydrobromic acid from sodium 2-pyridinediazotate by solution in concentrated hydrobromic acid and from 2-aminopyridinc by diazotization in the presence of bromine and concentrated hydrobromic acidd The method described here is essentially that of Craig. 

Lithium chloride Phosphorus oxybromide and oxychloride (phosphoryl bromide and chloride)... 

Bromination of 3-hydroxy-l,2,5-thiadiazoles 129 was achieved using phosphorus oxybromide however, vigorous conditions are required (Equation 21) <1996H(43)2435>. 

Dehydroxy-halogenation of thiazolidinedione (1) with phosphorus oxybromide led to 2,4-dibromothiazole (2) [3], whereas the same reaction conducted in DMF resulted in 2,4-dibromo-5-formylthiazole (3) [4],... 

Reaction with phosphorus pentabromide yields phosphorus oxybromide ... 

The residue in the distilling flask consists of phosphorus oxybromide (No. 82 c) which may be purified by distillation b.p. 193-195°C. The almost-white soKd melts at 56°G. 

Phosphorus oxybromide reacts slowly with water to yield orthophosphoric and hydrobromic acids. It dissolves readily in many organic solvents such as ether, benzene, and carbon tetrachloride. Because the bromide decomposes readily at high temperatures, it should always be melted in a hot water bath (m.p. 55 56°C), never with a flame. Prepared as described, the product contains traces of phosphorus tribromide which can be removed only by 6-fold high-vacuum distillation. 

Treatment of l,5-naphthyridin-2-one (125) with bromine and water gave the 3-bromo product. Similarly, the l,5-naphthyridin-4-one (126) afforded the 3-bromo compound under the same conditions.64 The 4-oxo compound (126) when reacted with phosphorus penta-bromide afforded 3,4,8-tribromo-l,5-naphthyridine. The reaction of compound 126 with phosphorus oxybromide gave the expected 4-bromo compound. 

Two products (128 and 129) were obtained when 1,6-naphthyridin-4-one (127) reacted with phosphorus pentabromide.143 It is presumed that 128 is the precursor of 129. The 4-bromo derivative was obtained when compound 127 was treated with phosphorus oxybromide. The 3-bromo-l,6-naphthyridin-4-one (130) was prepared in good yield from compound 127, and on reaction with phosphorus oxybromide the 3,4-dibromo-l,6-naphthyridine (131) could be obtained. The reaction of l,7-naphthyridin-8-one with phosphorus oxybromide is unique,144 since it appears to be the only example in this series, in which further bromination occurs with this reagent, affording 8-monobromo and 3,8-dibromo-l,7-naphthyridine. 

Chloro-l-formyl-l-cyclohexene has been prepared only by the action of phosphorus oxychloride (or phosgene) and di-methylformamide on cyclohexanone3-5 2-Bromo-l-formyl-l-cyclohexene has been synthesized by a method analogous to the above by the use of phosphorus oxybromide or phosphorus tribromide.6... 

A novel and efficient synthesis of 5-(hydroxymethyl)thiazole starting from 2,4-thiazolidinedione was performed with phosphorus oxybromide and DMF to give 2,4-dibromo-5-thiazolecarboxaldehyde in 72 % yield. Reduction of the aldehyde with NaBH4 and catalytic hydrogenation with Pd/C at room temperature afforded the desired product in excellent yield. [95SC2639]... 

Chloro-substituted thiazoles can be prepared by the reaction of phosphorus oxychloride with the corresponding 4-hydroxythiazoles. This method is also applicable for the preparation of 4-bromo-2-phenylthiazole. Conversion of 3-hydroxy-l,2,5-thiadiazoles into the bromo compounds can be achieved using phosphorus oxybromide, but vigorous conditions are required <1996H(43)2435>. 

Phosphorus oxybromide (95.5 g. or 0.33 mole) is added to a mixture of 45 g. (0.32 mole) of N-methylformanilide and 32.6 g. (0.2 mole) of 2-bromothiophene (p. 60). (Hood.) A vigorous reaction occurs, and the reaction flask is cooled until the rate of evolution of hydrogen bromide decreases, after which the mixture is heated on a steam bath for 1 hour. The mixture is cooled, neutralized with aqueous sodium... 

In detritylation with phosphorus pentabromide, an alkyl bromide, trityl bromide and phosphorus oxybromide are formed. This reaction may be used to locate the position of the trityl group. Phosphorus pentachloride reacts in a similar manner. 

It is reported that the procedure of v. Braun and Steindorff, Ber. 38, 2338 (1905), is a more satisfactory method of eliminating benzonitrile from the crude product. The distillate containing the alkylene bromide, benzonitrile, and phosphorus oxybromide is poured carefully into 90-100 cc. of water, with cooling and shaking. The resulting mixture is refluxed for eight to ten hours, with the occasional addition of 3-4 cc. of alcohol to decrease resinification. The product is then removed by steam distillation, washed with sodium carbonate solution, dried, and dis-... 

Phenyl- and 6-trifhioromethyl-l,4-dichlorophthalazine have also been prepared in good yield (43% and 84%, respectively) from the corresponding 6-substituted, 4-hydroxy-l-(2H)phthalazinones.117 118 Similarly, 1,4-dibromophthalazine was prepared by heating 4-hydroxy-l-(2H)phthalazinone with phosphorus pentabromide in 78-97% yield.115,11 However, treating 4-hydroxy-l-(2H)phtha-lazinone (48) with phosphorus oxybromide gives 1-bromophthalazine only (88% yield).115 116... 

Dehydroxy-halogenation of thiazolidinedione (1) with phosphorus oxybromide led to... 

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