The substituted R and R1 groups may be substituted at one or more available positions by one or more suitable groups such as, for example, alkyl groups having from 1 to 10 carbon atoms or from 1 to 6 carbon atoms, alkenyl groups having from 2 to 10 carbon atoms or 2 to 6 carbon atoms, aryl groups having from six to ten carbon atoms, halogen such as fluoro, chloro and bromo, and N, O and S, includi