Acetic Anhydride → 1-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)ethanone

HRID 975934Notes

Reaction equation

HRID 975934 reaction equation
[CH3:1][O:2][C:3]1[CH:4]=[C:5]2[C:10](=[CH:11][C:12]=1[O:13][CH3:14])[CH2:9][NH:8][CH2:7][CH2:6]2.[C:15](OC(=O)C)(=[O:17])[CH3:16]>N1C=CC=CC=1>[CH3:1][O:2][C:3]1[CH:4]=[C:5]2[C:10](=[CH:11][C:12]=1[O:13][CH3:14])[CH2:9][N:8]([C:15](=[O:17])[CH3:16])[CH2:7][CH2:6]2

Participants

4

Reactant 2

HCID 7918Acetic AnhydrideHCID 156236,7-Dimethoxy-1,2,3,4-Tetrahydroisoquinoline

Product 1

HCID 48395801-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)ethanoneYield 89%

Reagents, catalysts & solvents 1

HCID 1049PyridineSolvent

Procedure

To a stirred solution of 6,7-dimethoxy-1,2, 3,4-tetrahydroisoquinoline (3.00 g, 15.4 mmol, 1.00 equiv) in anhydrous pyridine (100 mL) under argon at room temperature was added acetic anhydride (14.5 mL, 154 mmol, 10.0 equiv) over 15 min. The resulting mixture was stirred at room temperature for 2 h, and then at reflux for 6 h. The volatiles were removed by rotary evaporation at 80° C. under high vacuum. The residue was flash chromatographed on silica gel (MeOH-CH2Cl2 8:92) to afford 3.21 g (89%) of viscous brown oil. The 1H NMR spectrum reflected the presence of two slowly interconverting conformers in a ratio of 1.2 :1 at room temperature. 1H NMR (300 MHz, CDCl3) for conformer 1: δ 2.18 (s, 3 H), 2.83 (t, J=5.9 Hz, 2 H), 3.67 (t, J=5.9 Hz, 2 H), 3.86 (s, 3 H), 3.87 (s, 3 H), 4.66 (s, 2 H), 6.63 (s, 1 H), 6.65(s, 1 H). For conformer 2:δ 2.19 (s, 3 H), 2.77 (t, J=5.9 Hz, 2 H), 3.81 (t, J=5.9 Hz, 2 H), 3.86 (s, 3 H), 3.87 (s, 3 H), 4.56 (s, 2 H), 6.59 (s, 1 H), 6.63 (s, 1 H).

Workup

  1. temperatureat reflux for 6 h
  2. customThe volatiles were removed by rotary evaporation at 80° C. under high vacuum
  3. customchromatographed on silica gel (MeOH-CH2Cl2 8:92)

Sources & evidence

ORD record
ord-1f897593c01242a0b8ed000dc137dd0c
Source dataset
uspto-grants-1997_03
Patent number
US05610174

Reaction notes

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