Pyrimidinyl-substituted amides and thioureas: syntheses, crystal structure and herbicidal activities.
BACKGROUND
The high herbicidal activities of [1,2,4]triazolo[1,5-c]pyrimidine and 2H-1,2,4-thiadiazolo[2,3-a]pyrimidine derivatives suggested the development of new fused heterocyclic compounds for application as herbicides.


RESULTS
Three series of pyrimidinyl-substituted thioureas (4) and amides (5, 6) were synthesized, and the typical crystal structure of a 2H-1,2,4-thiadiazolo[2,3-a]pyrimidine derivative (5a) was determined by X-ray diffraction. All the compounds were tested for herbicidal activity against selected weeds.


CONCLUSIONS
The series of fused heterocyclic amides 5a to 5d exhibited high herbicidal activities both against monocotyledonous weeds (Echinochloa crus-galli L., Sorghum bicolor (L.) Mönch., Digitaria sanguinalis (L.) Scop) and against dicotyledonous weeds (Amaranthus retroflexus L. and Brassica campestris L.) in pre-emergence treatments. In particular, compound 5b at low concentration still showed high inhibitory activity against A. retroflexus in pre-emergence treatment. Different substituents at the meta positions of the pyrimidine ring were found to affect the herbicidal activity.
Liu
Guo-Hua
GH
Department of Chemistry, College of Life and Environmental Science, Shanghai Normal University, Shanghai 200234, PR China. ghliu@shnu.edu.cn
Xue
Yun-Ning
YN
Lu
Xiao-Quan
XQ
Liu
Mou-Ming
MM
Wang
Wei-Ying
WY
Yang
Liang-Zhun
LZ
D000577:Amides / Q000138:chemical synthesis* / Q000737:chemistry; D006540:Herbicides / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D011743:Pyrimidines / Q000737:chemistry*; D013057:Spectrum Analysis; D013329:Structure-Activity Relationship; D013890:Thiourea / Q000737:chemistry*
D000577:Amides; D006540:Herbicides; D011743:Pyrimidines; D013890:Thiourea