By cyclocondensation of 2-methylamino-3-(o-chlorobenzoyl)-5-ethylthiophene (I) with ethyl glycinate hydrochloride (A) in pyridine.
By cyclization of 2-(N-methyl-2-aminoacetamido)-3-(o-chlorophenyl)-5-ethylthiophene (II) in pyridine - benzol - acetic acid. The starting thiophene (II) can also be obtained in two different ways both starting from the 2-methylamino-3-(o-chlorobenzoyl)-5-ethylthiophene (I): (a) The thiophene (I) is condensed with chloroacetyl chloride giving 2-(N-methylchloroacetamido)-3-(o-chlorobenzoyl)-5-ethylthiophene (III), which by treatment with NaI gives the corresponding iodoacetamido derivative (IV). This compound reacts with NaN3 giving the corresponding azide (V), which finally reacts with HBr affording the thiophene (II). (b) The reaction of the thiophene (I) with N-carbobenzoxyglycyl chloride gives the carbobenzoxy derivative (VI) which is then hydrolyzed with HBr to give (II).