2,6-Dichlorotoluene → 2,6-Dichlorobenzyltriphenylphosphonium bromide

Participants

Reaction Steps

A mixture of 2,6-dichlorotoluene (20.1 g, 0.125 mol), N-bromosuccinimide (24.6 g, 0.138 mol) and 2,2′-azobisisobutyronitrile (0.41 g, 2.50 mmol) in dry benzene (300 mL) under N2 was stirred at reflux for 6 h with continuous irradiation from a 100W lamp. The resulting reaction mixture was concentrated under vacuum (to 50 mL), cooled and filtered, washing with dry benzene. The filtrate (containing the crude benzyl bromide) was treated directly with triphenylphosphine (49.3 g, 0.188 mol), stirring at reflux for 17 h. After cooling, the precipitate was collected by filtration, washing thoroughly with dry benzene, then pentane, and dried under vacuum at 50° C. to give the phosphonium salt (511) as a cream powder (62.1 g, 99%), mp (benzene) 247–250° C. 1H NMR (CDCl3) δ 7.76 (m, 9H), 7.64 (m, 6H), 7.18 (s, 3H), 5.50 (d, J=14.3 Hz, 2H). Found: C, 60.03; H, 3.76. C25H2,BRCl2P requires C, 59.79; H, 4.01.

Provenance & Evidence