A compound represented by the following general formula (I): [wherein R1 and R2 independently represent hydrogen atom, or a group represented by the following formula (A): (wherein X1 and X2 represent hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom), provided that R1 and R2 do not simultaneously represent hydrogen atom; R3 and R6 represent an alkyl group; R4 and R7 represent hydrogen atom, an alkyl group, carboxy group, an alkoxycarbonyl group, or sulfo group; and R5 and R8 represents an alkyl group, an aryl group, an alkoxycarbonyl group, a vinyl group, a thienyl group, or a pyrrolyl group], or a salt thereof, which is usable for efficient screening for a chemical substance having applicability as a catalyst of the reaction of Michael addition.