The synthesis and chlorosulfonation of some diarylidene and heteroarylidene ketones with varying alicyclic ring size

A series of diarylidene and heteroarylidene ketones (1-20) was prepared using alicyclic ketones ((CH2)nC=O where n = 3 to 7). An improved synthesis of 2,4-dibenzylidenecyclobutanone (1) is described and the ease of preparation of the arylidene derivatives is considered in terms of the size of the alicyclic ring. Treatment of 2,5-dibenzylidenecyclopentanone (2) with chlorosulfonic acid (10 mole equivalents) afforded the 4,4'-bis-sulfonyl chloride (23), reducing the amount of chlorosulfonic acid (6 mole equivalents) produced the corresponding mono-sulfonyl chloride (24). Only the respective 4,4'-bis-sulfonyl chlorides (39, 45, 51) could be isolated from the diarylidene ketones derived from larger alicyclic rings. Attempted chlorosulfonation of 2,4-dibenzylidene cyclobutanone (1) gave a mixture of products which could not be clearly characterised. The sulfonyl chlorides were converted into stable sulfonamides (25-29, 35, 36, 38, 40-44, 46-48, 52, 54) by condensation with amines, and selected samples were screened for biological activity as potential insecticides, herbicides and fungicides. The orientation of sulfonation is discussed in relation to stereoelectronic factors and the relevant spectral data.