Pyridine → 3-Thiophenecarboxamide,N-ethyl-

A mixture of thiophene-3-carboxylic acid (20.0 g, 178 mmol), thionyl chloride (30 mL, 411 mmol), and catalytic DMF (5 drops) was stirred at RT overnight. This solution was concentrated under vacuum, and stripped several times from toluene to remove all traces of excess thionyl chloride. Ethyl amine hydrochloride (29.03 g, 356 mmol) was then added to a solution of this crude acid chloride dissolved in CH2Cl2 (50 mL). Pyridine (31.64 g, 400 mmol) was added, and after 1 h of stirring the reaction was washed with 10% HCl followed with water, dried (MgSO4), concentrated, and recrystallized from EtOAc/hexanes to give 14.9 g of N-ethyl-3-thiophenecarboxamide as a tan solid, a 76% yield. m.p. 115-117° C. 1.3M s-BuLi in cyclohexane (37.23 mL, 48.4 mmol) was added dropwise to a dry-ice/acetone cooled solution of N-ethyl-3-thiophenecarboxamide (3.41 g, 22 mmol) and TMEDA (5.62 g, 48.4 mmol) in THF (100 mL). After stirring for 30 min at -78° C., TMSCl (5.26 g, 48.4 mmol) was added in a single portion. The reaction was allowed to slowly warm to -10° C. over 1 h, then was quenched with dilute aq citric acid and extracted with ethyl acetate (3×). The combined organic solutions were dried (MgSO4), concentrated, and purified by HPLC with 3:7 EtOAc/hexanes to give 1.4 g of the title compound as a white solid, a 28% yield. m.p. 114-116° C.

1. concentrationThis solution was concentrated under vacuum
2. customto remove all traces of excess thionyl chloride
3. stirringafter 1 h of stirring the reaction
4. washwas washed with 10% HCl
5. dry with materialdried (MgSO4)
6. concentrationconcentrated
7. customrecrystallized from EtOAc/hexanes

ORD record

ord-67b993c214834024b26c6fcdf49c1258

Source dataset

uspto-grants-2000_12

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06166057