NEW MATERIAL: A compd. represented by formula I [wherein Z is 3-allyl-2- methyl-4-oxocyclopent-2-en-l-yl, 3-propagyl-2-methyl-4-oxocyclopent-2-en-1-yl, 5-benzoylfur-3-ylmethyl or a group represented by formula II (wherein X is, H, OH, OCH3 or ethynyl)] and its steric isomer.

EXAMPLE: 3,4,5,6-tetrahydrophthalimidomethyl 3,3-bis-(difluorometyl)-2,2- dimethylcyclopropanecarboxylate.

USE: This new material is an effective component of an insecticidal compsn. and shows especially high knock-down activity and repels an insect and a similar invertebrate harmful insect.

PROCESS: For example, 3,3-bis-(difluoromethyl)-2,2-dimethylcyclopropanecarboxylic acid represented by formula II and alcohol represented by the formula, ZOH are reacted in a solvent in the presence of an acid catalyst or a dehydrating agent to obtain the compd. represented by formula I.