Patent ID: 7863268

Claim:
A compound of formula (I) or a salt thereof, wherein R 1 and R 2 are, independently, NO 2 , CN, CONR 7 R 8 , COOR 9 , CHO, halogen, SO 2 NR 7 R 8 , OCF 3 , or trifluoromethyl; R 3 and R 4 are, independently each from other, H, or a methyl group; R 5 and R 6 are, independently each from other, a linear or branched aliphatic radical having 1-8 chain members, or R 5 and R 6 together represent a bivalent radical â€”(CR 9 2 ) m â€”, wherein m is 1-4, or R 5 and R 6 together represent the bivalent radical: R 7 , R 8 and R 9 are, independently H or a linear or branched aliphatic radical having 1-7 chain members, or phenyl.