Disclosed are compounds of Formula 2
wherein
A is C(R 3c )=C(R 3d );
R 3a , R 3b and R 3c are H;
R 3d is CH 3 ;
R 2 is pyridinyl, pyrimidinyl or thiazolyl, each optionally substituted with up to 3 substituents independently selected from the group consisting of halogen and C 1 -C 4 alkyl;
R 4 and R 5 are H; and
a is 1.
