Boron trifluoride etherate → 4-(3,4-Dinitrobenzyl)morpholine

Participants

Reaction Conditions

Reaction Steps

Sodium borohydride (3.36 g, 89 mmol, 2.1 eq.) was ground, placed in a nitrogen-flushed flask and suspended in THF (120 mL). After cooling to ˜0° C., boron trifluoride etherate (11.3 mL, 89 mmol, 2.1 eq.) was added via syringe. This reaction is mildly exothermic and some hydrogen evolution was noted. 4-(3,4-Dinitrobenzoyl)morpholine (11.91 g, 42 mmol, 1.0 eq.) was added as a solid in one portion, the vessel being rinsed with an additional portion of THF (20 mL). The ice-bath was removed and the suspension stirred at r.t. for 3 h before cooling again in ice. Methanol (100 mL) was added cautiously (hydrogen evolution) then the mixture was brought to reflux for 1 h. The mixture was concentrated in vacuo then the residue was partitioned between ethyl acetate (100 mL) and 1:1 saturated sodium bicarbonate solution/water (100 mL). The organic phase was separated, washed with water (50 mL) then brine (100 mL) and dried (MgSO4). The initial bicarbonate wash was extracted a second time with ethyl acetate (50 mL), this extract then being washed with the same aqueous washes used for the first extract before drying (MgSO4), combination and concentration to afford 10.97 g of crude material. Recrystallisation from methanol (45 mL, 10 mL wash) gave the title compound (9.34 g, 83%).

Provenance & Evidence