Alicyclic and heterocyclic carbamates

Abstract The development of heterocyclic carbamates with insecticidal activity is illustrated. The variation of compounds with a repellent effect range from aromatic amides to carbamates with pronounced insecticidal properties. Enolisable heterocyclic compounds, based on 3‐methyl‐pyrazolon or hydroxy‐pyrimidine, were tested, and dimetilan (2‐dimethylcarbamoyl‐3‐methylpyrazolyl‐5‐dimethylcarbamate) with strong stomach poison activity against houseflies, and Pyramate R (2‐n‐propyl‐4‐methyl‐pyrimidyl‐6‐dimethyl‐carbamate) with a good contact activity against houseflies and a low toxicity for warm‐blooded animals, were developed. The synthesis and purification of these two compounds led under certain conditions to isomers. A comparison of the insecticidal and toxicological properties is given. The insecticidal activity of a further class of carbamates (1‐alkylthio‐methyl‐3‐methyl‐pyrazolyl‐5‐dimethylcarbamates) is specified. For this type of compound, isomers with differences in activity and toxicity were obtained. A further class of compounds of low mammalian toxicity is obtained by condensation of 3‐methyl‐pyrazolyl‐5‐dimethylcarbamate with esters of the acrylic acid: they have a pronounced effect on Diptera and Homoptera. More favourable lack of toxicity toward warm‐blooded animals combined with a good insecticidal activity was observed in monomethylcarbamates compared with the corresponding dimethyl analogues, but the monomethylcarbamates proved to be much more susceptible to hydrolysis. The search for new compounds without this disadvantage led to other carbamates, i.e. those of the quinolines, from which GS 13798 is so far the most noteworthy representative. Despite its rather narrow spectrum, it has outstanding activity against sensitive and resistant cockroaches.