Patent ID: 8013169

Claim:
A compound of the formula: wherein R 1 is H, C 1-4 alkyl, or CF 3 ; and, R 2 and R 3 are independently H, C 1-4 alkyl, C 1-5 acyl, cyano, alkylsulfonamide or arylsulfonamide, R 4 is hydrogen or a stable substituent consisting of from 1 to 8 heavy atoms and any required hydrogen atoms, said heavy atoms being selected from the group consisting of C, N, O, S, F, Cl, Br, I and any combination thereof wherein the stable substituent is selected from the group consisting of alkyl, alkenyl, alkynyl, phenyl, alkoxy, mercaptoalkyl, acyloxy, amino, halo, CH 2 CN, CN, NO 2 and OH; and n is 0, 1, 2 or 3.