反应详情

(R)-8-Bromo-3-(N-isopropylamino)-5-methoxy-3,4-dihydro-2H-1-benzopyran (3.8 g, 11.3 mmol) was dissolved in anhydrous methanol (80 mL) and to this was propanal (8.1 mL, 0.113 mol) added. The reaction was cooled (ice-bath) then sodium cyanoborohydride (1.3 g, 20.3 mmol) was added, the pH was adjusted to 5, and the reaction was allowed to stir at room temperature overnight. The solvent was removed in vacuo, the remains were twice with diethyl ether. The combined ether portions were treated with brine, dried (Na2SO4) filtered, and taken into a 1M solution of Na2CO3 and then extracted the solvent removed in vacuo to give the crude residue. Chromatography on silica (eluent: 7% ethyl acetate/hexane) gave 3.75 g (97% yield) of the title compound as a clear oil [α]21D =-82.5° (C=0.1 CHCl3). GC-MS (70 eV) M=343 (29%). The hydrochloride salt was made by dissolving the base in diethyl ether and dropping an excess of an ethereal HCl solution. The salt was recrystallized from ethanol/diethyl ether to give a white solid. Mp: 177°-9° C.

1. additionadded
2. temperatureThe reaction was cooled (ice-bath)
3. customThe solvent was removed in vacuo
4. additionThe combined ether portions were treated with brine
5. dry with materialdried (Na2SO4)
6. filtrationfiltered
7. extractionextracted the solvent
8. customremoved in vacuo
9. customto give the crude residue