water in tetrahydrofuran; diethyl ether; ethanol to THF soln. of Sn compd. added BH3 (N2, room temp.),refluxed (4 h), added H2O,stirred (30 min),extd. (Et2O), dried (MgSO4),evapd. in vac.,heated with pentane,filtered ArB(OH)2; ArB(OH)2 recrystd. from H2O; identified by m. p., IR, NMR;

in dichloromethane mixing at -78°C, heating in sealed ampoule (2 d at room temperature, under inert gas); distn.;

210°C;

iodine in tetrachloromethane molar ratio of educts = 1:1, boiling under reflux;