Hydrochloric Acid → 2-Thiopheneglyoxylic acid

HRID 597276Notes

Reaction equation

HRID 597276 reaction equation
N([O-])=O.[Na+].[C:5]([C:8]1[S:9][CH:10]=[CH:11][CH:12]=1)(=[O:7])[CH3:6].Cl.P([O-])([O-])([O-])=[O:15].[Na+].[Na+].[Na+].N([O-])=O.NC(N)=O.[OH2:29]>C(OCC)(=O)C.C(Cl)Cl>[S:9]1[CH:10]=[CH:11][CH:12]=[C:8]1[C:5](=[O:7])[C:6]([OH:15])=[O:29]

Participants

10

Reactant 7

HCID 313Hydrochloric Acid2×HCID 946Nitrite2×HCID 962Water3×HCID 1176UreaHCID 69202-AcetylthiopheneHCID 24243Trisodium PhosphateHCID 23668193Sodium Nitrite2×

Product 1

HCID 776942-Thiopheneglyoxylic acid

Reagents, catalysts & solvents 2

HCID 6344DichloromethaneSolvent2×HCID 8857Ethyl AcetateSolvent

Procedure

A solution of sodium nitrite (35g; 0.5 mole) in water (100 ml.) was added steadily over 95 minutes to a stirred mixture of 2-acetylthiophene (25.1g; 0.2 mole) in 6N-hydrochloric acid (200ml) at 65°. 1.3M Trisodium phosphate (160 ml.) was then added over ca 3 minutes to raise the pH of the mixture to 1.8. Simultaneously, addition of a second portion of sodium nitrite (28g; 0.4 mole) in water (70 ml.) was commenced which took 75 minutes to complete. The pH was kept below 3.5 by addition of hydrochloric acid as required, during the nitrite addition, and was then lowered to 2. Urea (2g.) in water (10 ml.) was then added to decompose any excess of nitrite. The mixture was cooled to 20° and extracted first at pH 5.7 with methylene chloride (2 × 100 ml.) to give crude unreacted 2-acetylthiophene (3.6g; 14%), then at pH 2.7 with methylene chloride (3 × 100 ml.) to give crude thienoic acid (1.4g; 6%), and finally at pH 0.2 with methylene chloride (5 × 100 ml) followed by ethyl acetate (3 × 100 ml). These latter extracts were washed with saturated sodium chloride, and evaporated to dryness. Crystallisation of the residue from methylene chloride -- light petroleum (b.p. 40°-60°) gave thien-2-ylglyoxylic acid as two crops of bright yellow prisms [19.8g (63.5%), m.p. 92°-94°, and 3.0g (9.6%) m.p. 91°-93°].

Workup

  1. temperatureto raise the pH of the mixture to 1.8
  2. temperatureThe mixture was cooled to 20°
  3. extractionextracted first at pH 5.7 with methylene chloride (2 × 100 ml.)
  4. customto give crude unreacted 2-acetylthiophene (3.6g; 14%)
  5. washThese latter extracts were washed with saturated sodium chloride
  6. customevaporated to dryness
  7. customCrystallisation of the residue from methylene chloride

Sources & evidence

ORD record
ord-7590c33dd25549a0bd61001466d72de0
Source dataset
uspto-grants-1977_03
Patent number
US04013680

Reaction notes

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