Bromide ion → HCID 18976445, compound

Participants

Reaction Steps

A solution of 2-(2-bromoethyl)-1,3-dioxane (3.41 ml, 4.88 g, 25.0 mmol) in dry THF (15 ml) was slowly added to dry magnesium turnings (0.67 g, 27.5 mmol) and ~10 mg iodine at room temperature under N2. After heat evolved and the iodine color vanished, the contents were heated to reflux and the remainder of the bromide solution was added dropwise over 10 min. After 2 h reflux, the alkylmagnesium-bromide solution was cooled to room temperature and transferred via syringe to a solution of 2-bromo-5-methoxybenzyl bromide (3.50 g, 12.5 mmol) in 20 ml dry THF. The contents were cooled to -10° with ice-salt, treated with Li2 CuCl4 in THF (0.45 ml of 0.1M solution), and allowed to stir at room temperature overnight for convenience. After 19 h, the solvent was evaporated and the residue partitioned between ether and 5% NH4Cl. The ether layer was washed with 5% NH4Cl, water, and brine, then dried over MgSO4, filtered, and evaporated to yield 4.59 g of a pale yellow oil. The crude material was purified by column chromatography (140 g silica gel, 50% ether/petroleum ether as eluent) under "flash" conditions to yield 2.31 gm (58%) of the dioxane as a colorless oil; tlc (silica gel, 50% ether/petroleum ether) Rf 0.48. A dimeric by-product, 1,2-bis(2-bromo-5-methoxyphenyl)ethane, was obtained as a white solid (1.02 g, 41%); mp 98°-101°. TLC (silica gel, 50% ether/petroleum ether) Rf 0.63.

Provenance & Evidence