The present invention provides a method for preparation of a compound of the formula (I) useful as a fog restrainer for a silver halide light-sensitive material, especially for a heat-developing light-sensitive material and a synthetic intermediate for the fog restrainer. The method makes it possible to obtain the fog restrainer in good yield and in short steps. ##STR1## wherein, R.sup.1 is alkyl, cycloalkyl, or aryl, R.sup.2 and R.sup.3 are hydrogen atom or alkyl, R.sup.4 is hydrogen atom or acyl, and R.sup.1 and R.sup.4 may be bonded together to form 5- or 6-membered ring.
本发明提供了一种制备式(I)化合物的方法,该化合物可用作
银卤化物感光材料的防雾剂,特别适用于热显影感光材料,并提供了防雾剂的合成中间体。该方法可以在短时间内获得高产率的防雾剂。
其中,R1是烷基、环烷基或芳基,R2和R3是氢原子或烷基,R4是氢原子或酰基,而R1和R4可以结合形成5或6元环。