Tadalafil Impurity 19 synthesis
- Product Name:Tadalafil Impurity 19
- CAS Number:477970-21-1
- Molecular formula:C23H21N3O4
- Molecular Weight:403.43
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Yield:-
Reaction Conditions:
Stage #1: (6R,12aR)-2,3,6,7,12,12a-hexahydro-2-methyl-6-(3,4-methylenedioxyphenyl)-pyrazino[2',1':6,1]pyrido[3,4-b]indole-1,4-dionewith sodium hydride in tetrahydrofuran;mineral oil at 20; for 0.583333 h;
Stage #2: methyl iodide in tetrahydrofuran;mineral oil; for 3 h;
Steps:
6R,12aR)-6-(benzo[d][1,3]dioxol-5-yl)-2,7-dimethyl-2,3,12,12a-tetrahydropyrazino[1',2':1,6] pyrido[3,4-b]indole-1,4(6H,7H)-dione(4a)
To a suspension of NaH (60 % in mineral oil,2.68 mg, 0.067 mmol) in THF (0.5 mL) was added tadalafil1 (8.7 mg, 0.022 mmol) in dry THF (0.2 mL). The reaction was stirred for 35 minutes at room temperature before adding iodomethane (9.51 mg, 0.067 mmol), and then the reaction mixture was stirred for 3 hours. To the reaction was then added water and EtOAc. The aqueous layer was extracted 3x with EtOAc. The organics were combined, washed with brine (1x) and dried over Na2SO4. The solvent was concentrated. The crude material was added to a silica column and was eluted with 70-100% EtOAc in hexane to provide 4a (NEU-0000256) as a white solid. 1H NMR (500 MHz, CDCl3) δ 7.53 (d, J = 7.5 Hz, 1H), 7.29 (t, J =7.75 Hz, 1H), 7.25 (m, 1H), 7.16 (t, J = 7.25 Hz, 1H), 7.02 (s, 1H), 6.80 (, J = 2.0 Hz, 1H), 6.71 (d, J = 8.5 Hz, 1H), 6.65 (d, J = 6.5 Hz, 1H), 5.95 (s, 2H), 4.32 (dd, J= 11.5 Hz, J = 4.75 Hz, 1H), 4.15 (d, J = 18 Hz, 1H), 4.01 (d, J = 18 Hz, 1H), 3.55 (dd, J= 15.5 Hz, J = 4.5 Hz, 1H), 3.42 (s, 3H), 3.00 (s, 3H), 2.95 (dd, J= 15.5 Hz, J = 11 Hz, 1H). LCMS found 404.01, [M+H]+.
References:
Ochiana, Stefan O.;Gustafson, Alden;Bland, Nicholas D.;Wang, Cuihua;Russo, Michael J.;Campbell, Robert K.;Pollastri, Michael P. [Bioorganic and Medicinal Chemistry Letters,2012,vol. 22,# 7,p. 2582 - 2584] Location in patent:supporting information; experimental part