tuted or substituted alkenyl group preferably having 2 to 10 carbon atoms; and R4 is a halogen atom, a cyano group, a nitro group, an unsubstituted or substituted ester group preferably having 1 to 9 carbon atoms, an unsubstituted or substituted acyl group preferably having 1 to 9 carbon atoms, an alkyl group substituted with one or more electron attractive groups and preferably having as a total