Study On Synthesis, Crystal Structure And Pesticidal Activity Of Aroylthioureas

In the end of 1960s, the compounds CH₃(CH₂)_nCOHNCSNHR¹, whichexhibited good pesticidal activities through biological activities tests, weresynthesized by Schroepl E. In the later years, a mount of aroylthioureas were preparedby modifying the substituted groups of thiourea, and presented extensive biologicalactivities. During these years, the aeylthioureas, which displayed the activities of plantgrowth regulator, herbicide and fungicide, were synthesized. In order to find morecompounds possessing biological activities, two series aroylthioureas were designedand synthesized, and their pesticidal activities were also tested. Seven single crystalstructures of the compounds were obtained to supply the data for studying therelationship between the structure and biological activities of these compounds.The thesis includes two parts as follows:First, study on synthesis, crystal structure and pesticidal activities of2,4-dichlorophenoxyacetylthioureas.The compound 2,4-dichlorophenoxyacetylisothiocyanate was prepared by thereaction of 2,4-dichlorophenoxyacetylchloride derived from the chlorination of2,4-dichlorophenoxyacetic acid with sodium thiocyanate. Trearnent with the2,4-dichlorophenoxyacetylisothiocyanate with 6 different substituted arylaminesafforded six 2,4-dichlorophenoxyacetylthioureas which were confirmed by UV, IRand ¹H NMR. The single crystals ofâ… b,â… e andâ… f suitable for collecting data onthe X-ray diffraction machine were obtained. In the three single crystal structures, thebond lengths of S=C double bonds are among 1.626-1.645(?), O=C double bonds areamong 1.204-1.221(?) and N-C single bonds are among 1.330-1.425(?), indicating suchN-C single bonds possessing the characteristics of N=C double bond. There are twointramolecular N-H…O hydrogen bonds in each of the three crystal structures,making a five-membered ring edged with a six-membered ring. The C9-N1-C8 grouppart of the central thiourea group is just like a conjugated structure, at the end ofwhich arrange the oxygen atom of carbonyl group and the sulfur atom of thio-carbonyl group adopting the trans-conformation. The pesticidal activity test wascarried on the compounds(â… a-â… f) by dipping method, which showed that thecompoundâ… e exhibited better pesticidal activity with LC₅₀ being 305.80mg/L.Second, study on synthesis, crystal structure and pesticidal activity ofaroylthioureas.The compounds-aroylisothiocyanates were prepared by the reaction ofaroylchlorides derived from the benzoic acid, o-methylbenzoic acid and 2-furoic acidwith sodium thiocyanate. Treament with the aroylisothiocyanates with differentsubstituted arylamines afforded 12 aroylthioureas which were confirmed by UV, IRand ¹H NMR. The advantages and disadvantages between the method of reaction inliquid and the phase-transfer catalysis method were compared. The single crystals ofâ…¡c,â…¡e,â…¡g andâ…¡h suitable for collecting data on the X-ray diffraction machinewere obtained. The compoundâ…¡c changed into the compound2-benzoylamino-4,6-dichlorobenzothiazole when it crystallized from the DMF solvent,and the changing mechanism of this phenomenon was proposed to be nucleophilicsubstitution reaction. The oxygen atom of carbonyl group and the sulfur atom ofthio-carbonyl group adopt the trans-conformation. In the crystalsâ…¡c andâ…¡g, thereare two independent molecules (Molecule A and Molecule B) in a unit cell in eachcrystal. There are few differences of bond lengths and bond angles between the twoindependent molecules, but obvious differences of dihedral angles between them,which maybe contributed to free rotation degree of the C-C bond which connects thecentral part and phenyl ring. In the crystalâ…¡e, the intermolecular N-H…S hydrogenbonds link the molecules into a chain structure and form a R₂²(8) motif. The pesticidalactivity test was carried on the compounds(â…¡a-â…¡h) by dipping method, whichshowed that the compoundsâ…¡b andâ…¡c exhibited some pesticidal activity withLC₅₀ of the compoundsâ…¡b andâ…¡c being 144.61mg/L and 109.55mg/L, respectively.