Acetic Acid → 5-(Dimethyl)aminobenzo[b]thiophene

HRID 979564Notes

Reaction equation

HRID 979564 reaction equation
N[C:2]1[CH:10]=[CH:9][C:5]2[S:6][CH:7]=[CH:8][C:4]=2[CH:3]=1.C=O.[C:13]([BH3-])#[N:14].[Na+].[C:17](O)(=O)C>CC#N.CCOCC>[CH3:17][N:14]([CH3:13])[C:2]1[CH:10]=[CH:9][C:5]2[S:6][CH:7]=[CH:8][C:4]=2[CH:3]=1

Participants

7

Reactant 4

HCID 176Acetic Acid2×HCID 712FormaldehydeHCID 288032Benzo(b)thiophen-5-amineHCID 5003444Sodium cyanoborohydride

Product 1

HCID 139229055-(Dimethyl)aminobenzo[b]thiopheneYield 88%

Reagents, catalysts & solvents 2

HCID 3283Diethyl EtherSolventHCID 6342AcetonitrileSolvent

Procedure

To a stirred solution of 5-aminobenzo[b]thiophene (4.55 g, 0.03 mole) in CH3CN (175 ml) was added 37% aqueous formaldehyde (28 ml, 0.035 mole) followed by sodium cyanoborohydride (6.65 g, 0.105 mole). Glacial acetic acid (3.5 ml) was added in small increments over 15 minutes. After 1 hour, another 3.5 ml of acetic acid was added and after another 1 hour, the mixture was poured into ether (700 ml). The ethereal layer was separated, washed with lM KOH (3×) then with saturated NaCl solution, dried over anhydrous Na2SO4, and evaporated to dryness in vacuo. The residual dark oily solid was purified by chromatography on 800 ml of silica gel. Elution with 97 hexane:3 ethyl acetate afforded 4.6 g (88%) of 5-(dimethyl)aminobenzo[b]thiophene as a light yellow solid, m.p. 52°-54° C.

Workup

  1. customThe ethereal layer was separated
  2. washwashed with lM KOH (3×)
  3. dry with materialwith saturated NaCl solution, dried over anhydrous Na2SO4
  4. customevaporated to dryness in vacuo
  5. customThe residual dark oily solid was purified by chromatography on 800 ml of silica gel
  6. washElution with 97 hexane

Sources & evidence

ORD record
ord-bd7cf467c2394af8b05fbc7e7b7b1d34
Source dataset
uspto-grants-1987_05
Patent number
US04668697

Reaction notes

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