aluminium trichloride; tert-butylamine borane in dichloromethane T=0°C; 0.75 h;

aluminiumchloride in dichloromethane addn. of tert.-butylamine borane to suspn. of anhyd. AlCl3 at 0°C (20 min.), addn. of soln. of the 1,3,2-benzodioxaborin in CH2Cl2, allowed to react at 0°C for 45 min; addn. of cold dilute HCl; extn. with CH2Cl2, organic extracts dried over anhyd. MgSO4, concd., chromy. (silica gel, 10percent ethyl acetate in hexane);