boric acid in toluene 24 h; Reflux;

in toluene under dry N2 using std. vac.-line Schlenk technique; placed into round-bottom flask attached to Dean-Stark app. with reflux condenser, refluxed for 24 h; product distd. under high vac.;

in not given byproducts: H2O; (Ar);

in not given stoich. quantities of B(OR)3 and boric oxide heated to 110 °C under dry N2 until a clear liquid is obtained;