ydrogen or a halogen atom; and R1 is a halogen atom or is an alkyl, cyclic alkyl, or aryl group having from 1 to 10 carbon atoms; such alkyl or aryl groups may optionally be halogenated and may contain one or more heteroatoms and may be partially-, fully-, or non-halogenated provided, however, that when X is a hydrogen atom R1 contains an allylic carbon atom relative to the ??-unsaturation and tha