The compound of claim 1, wherein R3 is hydrogen; R2is lower alkyl optionally substituted with halogen, hydroxy, lower alkyoxyimino or lower alkoxy; cycloalkyl; halogen; lower alkoxy optionally substituted with halogen; or lower alkylthio; R3 is lower alkoxy optionally substituted with aryl, hydroxy, cyano, amino, lower alkoxyxcarbonylamino, lower alkylsulfonylamino or carbamoylamino; R4 is a group