反应条件
potassium hydroxide; N-benzyl-N,N,N-triethylammonium chloride; hydrogen bromide; potassium bromide; sodium nitrite 1.) water, -12 deg C, 8 h; 2.) ethanol, -20 deg C 2 h, then 0 deg C, 14 h; 3.) CH2Cl2, r.t., 20 h; Yield given. Multistep reaction;