Compounds of the formula wherein R1-R5 are independently selected from hydrogen, alkyl of 1 to 6 carbon atoms, alkenyl of 2 to 6 carbon atoms, alkynyl of 2 to 6 carbon atoms, perhaloalkyl of 1 to 6 carbon atoms, cycloalkyl of 3 to 10 carbon atoms, heterocycloalkyl of 3 to 10 carbon members, aryl, heteroaryl, halogen, —CN, —NO2, —CO2R6, —COR6, —OR6, —SR6, —SOR6, —SO2R6, —CONR7R8, —NR6N(R7R8), —N(R7R8) or W—Y—(CH2)n—Z; or R2 and R3 or R3 and R4, taken together form a 3 to 7 membered heterocycloalkyl or 3 to 7 membered heteroaryl; R6 and R7 are independently hydrogen, alkyl of 1 to 6 carbon atoms, perhaloalkyl of 1 to 6 carbon atoms, or aryl; R8 is hydrogen, alkyl of 1 to 6 carbon atoms, perhaloalkyl of 1 to 6 carbon atoms, cycloalkyl of 3 to 10 carbon atoms, heterocycloalkyl of 3 to 10 members, aryl or heteroaryl, or R7 and R8, taken together may form a 3 to 7 membered heterocycloalkyl; A is heteroaryl.