where L is a leaving group, and wherein R2 is selected from the group consisting of C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, (4- to 10-membered heterocyclic) C1-C6 alkyl, (4- to 10-membered heterocyclic) C2-C6 alkenyl, (4- to 10-membered heterocyclic) C2-C6 alkynyl, (C6-C10 aryl) C1-C6 alkyl, (C6-C10 aryl) C2-C6 alkenyl, and (C6-C10 aryl) C2-C6 alkynyl wherein said alkyl moieties of the foreg