1,3,S-Triazapenta-l ,Cdienes of formula Ar-N=CH-N(R)tCH=N-Ar', are a new group of biologically active compounds. Various general methods for their preparation are described and their physical and chemical properties, including stability over range of pHs, are discussed. The unsymmetrical 1,3,5-triazapenta-1,Cdienes (Ar # Ar') are unstable; insolution, particularly, they equilibrate to the corresponding stable symmetrical analogues.Structure-activity relationships in laboratory tests against Boophilus microplus and Tetranychus urticae are discussed. Problems in the synthesis of ring-[14C]amitraz; [ 1,5-di-(2,4-dimethylphenyl)-3-methyl-1,3,5-triazapenta-1 ,Cdiene], an active member of the group, are outlined.

We wish to report the discovery of high acaricidal activity of a new compound, 1,5-di-(2,4-dimethylphenyl)-3-methyl-1,3,5-triazapenta-l,4-diene (proposed common name azaform) (I; Ar = 2,4-dimethylphenyl, R = Me). It can be prepared in good yield in a ArN=CHOEt + ArN=CHNHR 2ArN=CHNHR -..* / k 2 R I ArN=CHNCH=NAr (I) CulO catalyst / ArNC + ArN=CHNHRnumber of ways, the main routes being shown above. The structure was confirmed by elemental analysis, molecular weight determination, i.r., n.m.r., U.V. and mass spectrometry. These synthetic methods appear to be applicable to a wide range of compounds with various substituents in the aromatic nucleus. 1,3,5-triazapenta-l74-dienes with different substituents in each ring were obtained by the use of the appropriate starting materials. Rather surprisingly, slow equilibration of these unsymmetrical compounds with the corresponding symmetrical 1,3,5-triazapenta-l ,4-dienes took place in the dry state, and this process was rapidly accelerated in solution.The new acaricide belongs to a class of hitherto little-known compounds. Earlier workerslaZ prepared a number of 2,4-diaryl-1,3,5-triazapenta-l,3-and 1 ,4-dienes by alternative methods, but these compounds (I) are among the first examples of 2,4-unsubstituted derivatives. A recent publication3 describes compounds in which Ar and R in formula I above are replaced by an aliphatic or cycloaliphatic grouping. 679

Methods of synthesis and insecticidal properties of a series of aryl N‐acyl‐N‐methylcarbamates are described. There is evidence to suggest that the usual mode of action involves de‐acylation within the insect, although the acyl group may initially aid penetration to the site of action. An unexpected finding was that the acyl derivatives were generally less toxic to mammals than the parent carbamates. The persistence of 3‐s‐butylphenyl N‐methylcarbamate on foliage was considerably improved by the introduction of a phenoxyacetyl group. However, acylation did not improve the outstanding activity and persistence on sheep fleece of the blowfly larvicide Butacarb (3,5‐di‐t‐butylphenyl N‐methylcarbamate).