NEW MATERIAL: A compound represented by the formula I (wherein each of R1 to R3 is a 1-22C alkyl group and the total number of carbon atoms of R1 to R3 is 10 to 24).

USE: Useful for preparing 2-amino-4-chloro-3-cyano-5-formylthiophene which is an intermediate for producing azo dyes and represented by the formula II.

PREPARATION: Such a compound represented by the formula I is prepared by allowing malononitrile to react with chloroacetyl chloride and the corresponding trialkylamine concurrently, preferably at 0 to 20°C. The preparation of the compound represented by the formula II comprises: subjecting a compound represented by the formula I to cyclization with hydrogensulfide or another sulfide to obtain the 4-hydroxythiophene derivative represented by the formula III; allowing the resulting derivative represented by the formula III to react with a mixture of N,N-dimethylformamide and phosphoryl chloride to obtain a reaction product, i.e., N,N-dimethyl-N'-(4-chloro-3-cyano-5-formyl-2- thienyl)-formamidine represented by the formula IV; and then, directly hydrolyzing the resulting compound represented by the formula IV without isolating it, with an acidic medium to prepare the objective compound represented by the formula II.