Phosphorous tribromide

Doxapram Doxapram, l-ethyl-4-(2-morpholinoethyl)-3,3-diphenyl-2-pyrrolidinone (8.2.4), is synthesized in the following manner. Diphenylacetonitrile in the presence of sodium amide is alkylated with l-ethyl-3-chlorpyrrolidine, giving (l-ethyl-3-pyrrolidinyl) diphenylacetonitrile (8.2.1). Acidic hydrolysis of the nitrile group gives (l-ethyl-3 pyrrolidinyl)diphenylacetic acid (8.2.2). Reacting this with phosphorous tribromide... 

LI Propargyl Bromide from Propargyl Alcohol and Phosphorous Tribromide... 

By the action of water upon phosphorous tribromide F"Br, + 80H, P OHHo, + 8HBr. 

Allylio monobromido can only bo obtained by the action of phosphorous tribromide on allylic alcohol —... 

Phosphorous tribromide Phosphorus bromide (8) Phosphorous tribromide (9) (7789-60-8)... 

The heart of the preparation of capsaicin is a malonic ester synthesis. The first step is bromination of the primary alcohol by phosphorous tribromide. The resulting primary alkyl bromide is used to alkylate the sodium salt of diethyl malonate. A substituted malonic acid derivative is obtained following basic hydrolysis of the ester groups. 

Alcohols can be converted to alkyl halides by reaction with thionyl chloride, SOCI phosphorous trichloride, PCI phosphorous pen-tachloride, PCI or phosphorous tribromide, PBr3. For example, ethyl chloride or ethyl bromide can be prepared from ethyl alcohol via reactions with sulfur and phosphorous halides. 

Because thionyl bromide is relatively unstable, alkyl bromides are normally prepared by reacting the alcohol with phosphorous tribromide (PBr3). 

This reaction proceeds via a two-step mechanism. In the first step, the alcohol reacts with the phosphorous tribromide. 

Carboxylic acids react with phosphorous trichloride (PC13), phosphorous pentachloride (PC15), thionyl chloride (SOCl2), and phosphorous tribromide (PBr3) to form acyl halides. 

Solanesol (10 g) was dissolved in 9.5 ml hexane and 13.5 ml diethyl ether containing 1.3 ml pyridine at 0 to 5 °C and 1.8 ml phosphorous tribromide dissolved in 13 ml hexane added over 30 minutes. The mixture was stirred 3 hours, added to ice water, and stirred an additional 10 minutes. The phases were separated, the aqueous layer extracted with diethyl ether, washed with 5% NaHC03, concentrated, and 11 g product isolated. 

Pyridones or hydroxypyridines can readily be converted to the corresponding halide by a number of different reaction conditions [24], The use of phosphorous trichloride for transformation was demonstrated in the conversion of 72 to chloride 73. The exchange of chlorine for iodine, as in 74, has already been discussed (vide supra). The corresponding bromide could be obtained using phosphorous tribromide or phosphorous pentabromide, as in the conversions of 72 to 75 and 76 to 77. 

The steric course of additions of amines and alcohols to acetylene dicarboxylic ester was studied under various conditions. Secondary amines gave stereospecifically cis addition product. Nitrosyl formate can be generated in situ in the presence of an olefin to yield the nitrosoformate which on hydrolysis affords the hydroxynitroso compound in high yield. Transoximination gave the a-hydroxy ketone. Phosphorous tribromide can be added to olefins to yield 1 1 adducts with uv irradiation, peroxides, or heat as initiators ... 

Acid bromides (chlorides) Catechyl phosphorous tribromide (trichloride). Adamantane Aluminum bromide. 

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