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.

Chemical control, by dipping or spraying infested cattle with ixodicidal compounds, is the only practicable method of dealing with the cattle tick problem in the short term.Widespread exposure to ixodicidal compounds, often at subeffective concentrations, has resulted in the selection of resistant strains from tick populations.A situation has now been reached where cattle ticks in widely separated parts of the world have shown a capacity to develop resistance to most of the currently available chemical classes of ixodicide. There is a very real probability that these resistant strains will eventually replace susceptible tick populations, particularly in those areas where the cattle tick problem is already most acute. Research and development of new chemical groups of compounds with high ixodicidal activity and low mammalian toxicity is a matter of some urgency.In this review, the biological background of the tick problem is outlined. A brief history of the development of tick resistance to arsenic, organochlorine, organophosphorus and carbamate compounds is given. Reference is made to the underlying biochemical mechanisms involved. Some of the human factors affecting the development of tick resistance are examined and future prospects are assessed.

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Recent research on the control of animal ectoparasites with amitraz is summarised and reference made to its expellent action. Tickicides are an essential requirement for the rearing of cattle in tropical and sub‐tropical regions. The use of amitraz in these areas is well documented. More recently advantage has been taken of its broad acaricidal and insecticidal spectrum to develop the compound for use against lice, keds and, in particular, mites parasitic on farm animals. The outstanding miticidal activity of amitraz has been shown to extend to demodectic mange on dogs. Field trials in Central Europe and the Mediterranean region are used to illustrate the problem of animal pest control within the limits imposed by established farm practices. Finally, mention is made of some attempts to utilise the pesticidal properties of amitraz in less conventional ways, including pasture spraying for the control of ticks.

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