Reaction #2467976

Reaction equation

methyl 3-[(dimethylamino)diazenyl]-5-phenylthiophene-2-carboxylate

sodium hydroxide

HCl

→

solid

Yield 64.2%

3-[(dimethylamino)diazenyl]-5-phenylthiophene-2-carboxylic acid

Yield 64.2%

Solvents

methanol

water

Conditions

Workup

1. 1
   workup.ADDITIONThe mixture was diluted with ice cold water
2. 2
   workup.STIRRINGThe mixture was stirred for 30 min
3. 3
   Filtrationthe precipitated solid was filtered
4. 4
   Washwashed with water
5. 5
   Otherdried
6. 6
   OtherThe solid was chromatographed over silica gel column
7. 7
   Otherto give the product
8. 8
   OtherThe crude solid was recrystallized from hexane-chloroform

Procedure

To a solution of methyl 3-[(dimethylamino)diazenyl]-5-phenylthiophene-2-carboxylate (1.8 g, 6.22 mmol) in methanol (50 mL) was added a solution of sodium hydroxide (1.24 g, 31.1 mmol) in water (15 mL) and stirred at rt for 16 h. The mixture was diluted with ice cold water and acidified with dil. HCl. The mixture was stirred for 30 min and the precipitated solid was filtered, washed with water and dried. The solid was chromatographed over silica gel column using hexane-ethyl acetate (70:30) as eluents to give the product. The crude solid was recrystallized from hexane-chloroform to give the product as a pale pink color solid (1.1 g, 61%), mp 162-166° C. IR (neat)νmax. 2923, 2853, 1708, 1260, 1220, 1173, 1042, 1020, 879, 836 cm−1; 1H NMR (400 MHz, CDCl3): δ 12.15 (1H, br s), 7.58-7.60 (2H, m), 7.44 (1H, s), 7.32-7.40 (3H, m), 3.65 (3H, s), 3.25 (3H, s); 13C NMR (100 MHz, CDCl3): δ 162.8, 153.3, 149.7, 133.3, 129.1, 129.0, 125.9, 120.1, 113.4, 44.3, 37.0; LC-MS (positive ion mode): m/z 298 (M+Na)+.

Source