The pyrethrins and related compounds. Part XXXII. Replacement of the central ester link

This paper, and the two following, report a detailed examination of the effect of replacement of the central link in pyrethroids by isosteric or isoelectronic groups, and how the resulting change in insecticidal activity depends on the particular groups present in the other parts of the molecule. In this first paper, a wide range (42 variations) of central groups in different combinations are synthesised and tested. Results indicate that with conventionally pyrethroidal acid and alcohol fragments in the molecule, some isosteric replacements are tolerated, but most other variations are unsuccessful, Particularly interesting central groups are COCH2 and CHCHCH2(E).