ChemicalBook CAS DataBase List (R)-2,3,6,7-Tetrahydro-1H-pyrazino[2,1-a]isoquinolin-4(11bH)-one

(R)-2,3,6,7-Tetrahydro-1H-pyrazino[2,1-a]isoquinolin-4(11bH)-one synthesis

5synthesis methods

Product Name:(R)-2,3,6,7-Tetrahydro-1H-pyrazino[2,1-a]isoquinolin-4(11bH)-one
CAS Number:55375-92-3
Molecular formula:C12H14N2O
Molecular Weight:202.25

4H-Pyrazino[2,1-a]isoquinolin-4-one, 1,2,3,6,7,11b-hexahydro-2-[(2S)-2-(6-methoxy-2-naphthalenyl)-1-oxopropyl]-, (11bR)-

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(R)-2,3,6,7-Tetrahydro-1H-pyrazino[2,1-a]isoquinolin-4(11bH)-one

55375-92-3
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Yield: 88%

Reaction Conditions:

with phosphoric acid in water at 150; for 0.333333 h;Microwave irradiation;Reagent/catalyst;

Steps:

(R)-(-)-1,2,3,6,7,11b-Hexahydro-4H-pyrazino[2,1-a]isoquinolin-4-one 3a
General procedure: Compound 2a (100mg, 0.241mmol) was suspended in 85w/w H₃PO₄ (2mL) in a proper vial which was heated to an external temperature of 150°C over a 3min period ramping up to a microwave power of 300W (Synthos 3000). The vial was held at this temperature for 20min to a microwave power of 85W. The mixture was cooled to 4°C, poured into crushed ice (15mL) and an aqueous solution of 5M NaOH was added to pH 12. The aqueous layer was extracted with dichloromethane (3×15mL). The organic layers were combined, dried over Na₂SO₄, filtered, and concentrated. The residue was purified by column chromatography (SiO₂, dichloromethane-methanol gradient from 100:0, v/v to 90:10, v/v). A white crystalline product was obtained (43.1mg, 88% yield). mp 124-126°C. [α]D=-306.1[α]D=-306.1 (c 1, CHCl₃). ¹H NMR (400MHz, CDCl₃) δ 7.25-7.10 (m, 4H, HC_10,9,8,11), 4.86 (ddd, J=12.5, 5.1, 2.6Hz, 1H, HC₆), 4.79 (dd, J=10.0, 4.6Hz, 1H, HC₁₁_b), 3.73 (ddd, J=13.0, 4.7, 1.4Hz, 1H, HC₁), 3.72 (AB, J=17.6Hz, 1H, HC₃), 3.52 (AB, J=17.3Hz, 1H, HC₃), 3.03-2.93 (m, 1H, HC₇), 2.92-2.85 (m, 1H, HC₁), 2.87-2.79 (m, 1H, HC₆), 2.78-2.70 (m, 1H, HC₇), 1.98 (s, 1H, HN₂)ppm. ¹³C{¹H} NMR (101MHz, CDCl₃) δ 167.4 (C₄), 135.1 (C₇_a), 134.3 (C₁₁_a), 129.5 (C₈), 127.1 (C₉), 126.7 (C₁₀), 124.8 (C₁₁), 57.0 (C₁₁_b), 50.1 (C₃), 49.9 (C₁), 38.9 (C₆), 28.9 (C₇)ppm. IR ν_max 3319, 2878, 1618, 1432cm^-1. MS (EI) m/z (relative intensity, %) 202 (M⁺, 20), 173 (76), 145 (100), 131 (71), 117 (33), 103 (16), 77 (17). HRMS (EI) Calcd for C₁₂H₁₄N₂O (M⁺): m/z 202.1101, Found: 202.1102. Anal. Calcd for C₁₂H₁₄N₂O: C, 71.26; H, 6.98; N, 13.85. Found: C, 71.30; H, 6.92; N, 14.02.

References:

Cedillo-Cruz, Alberto;Aguilar, Maria Isabel;Flores-Alamo, Marcos;Palomares-Alonso, Francisca;Jung-Cook, Helgi [Tetrahedron Asymmetry,2014,vol. 25,# 2,p. 133 - 140]

1,2,3,6,7,11B-HEXAHYDRO-4H-PYRAZINO(2,1-A)ISOQUINOLINE-4-ONE

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References