Hydrochloric Acid → 7-Fluoro-1,3-dihydro-1-hydroxy-2,1-benzoxaborole

Participants

Reaction Conditions

Reaction Steps

3-fluorobenzyl alcohol (3.5 parts; 0.028M) was stirred in THF (100 ml) containing tetramethylene ethylenediamine (10.2 ml; 0.067M). After cooling to -78° C., sec-butyl-lithium (77 ml of 0.8M solution in cyclohexane ex Aldrich; 0.061M) was slowly added over 45 min at between -78° and -65° C. with stirring under a nitrogen blanket. After 1 hour at -78° C., tributyl borate (16.78 ml; 0.061M) was added dropwise and the reactants stirred under nitrogen for 16 hrs allowing the temperature to slowly raise to 20° C. Dilute hydrochloric acid was added to bring the pH to about 12 and the aqueous phase separated and washed with diethylether. The pH of the aqueous phase was then acidified to about pH 2 with hydrochloric acid and extracted with ether (3×100 ml). These ether extracts were washed with saturated brine, dried over magnesium sulphate and the ether evaporated whereupon the product separated as a pale solid (2.6 parts; 62% theory) mp=132°-134° C. after recrystallisation from aqueous methanol.

Provenance & Evidence