optionally substituted with 1 3 groups of r a r 2 is hydrogen c 1 6 alkyl and c 3 10 cycloalkyl taken together with any intervening atoms can form a 3 to 7 membered carbocyclic or heterocyclic ring saturated or unsaturated said heterocyclic ring containing 1 2 heteroatoms independently chosen from o c o s so so 2 n or nr 2a and optionally substituted by 1 3 ra groups r 2a is hydrogen and c 1 6 alkyl r 3 and r 3a are independently hydrogen halo c 1 6 alkyl c 3 10 cycloalkyl and c 6 10 aryl said aryl and alkyl optionally substituted with 1 3 groups of r a or r 3 and r 3a taken together with any intervening atoms can form a 3 to 7 membered carbocyclic or heterocyclic ring saturated or unsaturated said heterocyclic ring containing 1 2 heteroatoms independently chosen from o c o s so so 2 n or nr 2a and optionally substituted by 1 3 r a groups r 4 is hydrogen halo c 1 6 alkyl and trihaloalkyl r a represents c 1 6 alkoxy c 1 6 alkyl cf 3 nitro amino cyano c 1 6 alkylamino or halogen and n represents 1 3 in one embodiment of this invention r 1a and r 1 independently are hydrogen tert butyl.