Phentermine → 3-(1,1-Dimethyl-2-phenyl-ethylamino)-4-(4-methoxy-phenyl)-cyclobut-3-ene-1,2-dione

HRID 843036Notes

Reaction equation

C(O[C:5]1[C:6](=[O:18])[C:7](=[O:17])[C:8]=1[C:9]1[CH:14]=[CH:13][C:12]([O:15][CH3:16])=[CH:11][CH:10]=1)(C)C.[CH3:19][C:20]([NH2:29])([CH3:28])[CH2:21][C:22]1[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=1>C(O)C>[CH3:28][C:20]([NH:29][C:5]1[C:6](=[O:18])[C:7](=[O:17])[C:8]=1[C:9]1[CH:10]=[CH:11][C:12]([O:15][CH3:16])=[CH:13][CH:14]=1)([CH3:19])[CH2:21][C:22]1[CH:27]=[CH:26][CH:25]=[CH:24][CH:23]=1

Participants

Conditions

Temperature: 70 °C

Procedure

To a solution of 3-isopropoxy-4-(4-methoxy-phenyl)-cyclobut-3-ene-1,2-dione (0.150 g, 0.609 mmol) in ethanol (3 mL) was added 1,1-dimethyl-2-phenyl-ethylamine (0.182 g, 1.22 mmol). The mixture was stirred at 70° C. overnight then filtered hot through a pad of silica gel. The filtrate was concentrated and the resulting residue was recrystallized from ethyl acetate/hexanes to give 0.170 g (83%) of the title product as a tan solid: m.p. 150-151° C.; 1H NMR (DMSO-d6) δ 8.28(s,1H), 8.00(m,2H), 7.28(m,2H), 7.26(m,1H), 7.13(m,2H), 7.09(m,2H), 3.82(s,3H), 3.10(s,2H), 1.42(s,6H); IR (KBr) 3420, 2950, 1775, 1715, 1650, 1570, 1410, 1252, 1200, 1045, 850, 740, 700, 602, 530 cm−1; MS (m/z) 335 [M+].

Workup

filtrationthen filtered hot through a pad of silica gel
concentrationThe filtrate was concentrated
customthe resulting residue was recrystallized from ethyl acetate/hexanes

Sources & evidence

ORD record: ord-e0820b120f7342ac9be7be848eecf028
Source dataset: uspto-grants-2002_04
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US06376555B1

Reaction notes

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