sodium amalgam in toluene under inert atm. chlorocatecholborane was dissolved in toluene, Na/Hg amalgam was added and heated at 90°C under N2 for 3 h; soln. was filtered and evapd.;

sodium amalgam in toluene under inert atm. to suspn. catechol in toluene at 0°C BBr3 was added, react. mixt. was allowed to warm to room temp., solvent was removed, residue was dissolved in toluene, Na/Hg amalgam was added and heated at 90°C under N2 for 3 h; soln. was filtered and evapd.;

sodium amalgam in n-heptane; toluene byproducts: HCl; under inert atm. to soln. catechol in toluene at 0°C soln. BCl3 in heptane was added dropwise, soln. was concd., Na/Hg amalgam was added,heated at 90°C under N2 for 5 h; soln. was filtered and evapd.;

in hexane N2-atmosphere; addn. of excess substituted catechol to B-compd. (room temp., stirring); dropwise addn. of excess 1 M HCl in Et2O, stirring at room temp. for 5 h, extn. into hexane, filtration (Celite), solvent removal (vac.); elem. anal.;