[4836-12-8] · C16H22BrClN2O4 · Bromonium Di-sym-collidine Perchlorate · (MW 421.72)
Alternate Names: bromonium dicollidine perchlorate; bis(collidine)bromonium perchlorate.
Physical Data: mp 230 °C.
Solubility: sol chloroform; insol ether.
Form Supplied in: fine colorless crystalline powder.
Preparative Method: it is important in the preparation of this reagent to be sure that conditions are anhydrous, otherwise bromine tends to be reliberated. Silver di-sym-collidine perchlorate is prepared by adding sym-collidine (20 mL) to a solution of silver nitrate (9 g) and sodium perchlorate (11 g) in 100 mL of water, while stirring vigorously, to give a curdy white precipitate. After washing repeatedly with water, the product is washed with ethanol and ether and finally dried under vacuum over P2O5. The yield is quantitative. Silver di-sym-collidine perchlorate (13.47 g, 30 mmol) is suspended in 150 mL of chloroform and 1 mL of sym-collidine. Bromine (1.65 mL, 30 mmol) is added. Silver bromide rapidly precipitates and is filtered through Celite. The clear pale-yellow filtrate gives a fine, white crystalline precipitate on the addition of ether. The crystals are dried under high vacuum.
Handling, Storage, and Precautions: perchlorates are potentially powerful explosives. This compound detonates on strong heating and so due precautions1 must be taken. The compound is stored under anhydrous conditions. This reagent should be handled in a fume hood.
Reaction of D-glucal triacetate (2) with equimolar amounts of methanol and bromonium di-sym-collidine complex (1) dissolved in chloroform gives virtually quantitative yields of acetylated methyl 2-deoxy-2-bromoglycosides. Unlike pyridine or 2-methylpyridine, the steric hindrance to N-glycoside formation provided by the methyl groups at the 2- and 6-positions of sym-collidine is required for successful O-glycoside synthesis. If 2,3,4,6-tetra-O-acetyl-b-D-glucose (3) is used as the alcohol, the 2-deoxy-2-bromo disaccharide heptaacetate (4) is formed (eq 1). Deacetylation with Triethylamine in aqueous methanol followed by hydrogenolysis with Palladium on Carbon as the catalyst affords b-D-glucopyranosyl-2-deoxy-a-D-arabino-hexopyranoside (2-deoxyneotrehalose), isolated as the crystalline heptaacetate (5).
This reagent can effect the stereo- and regiospecific functionalization of alkenes to furnish cis-1,2-methylamino alcohols in protected form. For example, unsaturated N-(R)-p-Methoxyphenethylamides were subjected to the bromolactamization sequence involving the use of Tapan Ray Sigma Radiochemical Co., St. Louis, MO, USA
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N-(R)-p-Methoxyphenethylamides were subjected to the bromolactamization sequence involving the use of
Sigma Radiochemical Co., St. Louis, MO, USA