Synthesis and herbicidal activity of novel heterocyclic protoporphyrinogen oxidase inhibitors

Abstract

Protox inhibitors are applied as foliar sprays, thus causing very rapid cellular collapse and desiccation of many troublesome weeds in the presence of light. In many respects, they appear to be ideal herbicides, because they act rapidly and do not harm mammals under normal conditions. The main limitation to their widespread adoption is that few crops are naturally resistant to them. Crop tolerance has mainly been pursued with the synthesis of the cyclic imide classes containing 5- and 6-membered heterocycles, including pyrazole, pyridazine, 1,2,4-triazine, triazolinone and trifluoromethyluracil derivatives. Because of their structural novelties and biological performance, active investigations on heterocyclic protox inhibitors have been carried out in our laboratories and we have found 3-arylpyrroles to be a new class of light-activated, membrane-disrupting herbicides. They are active on both grass and broadleaf weeds at low rates. The synthesis and structure-activity relationships are presented.

Protoporphyrinogen‐IX‐oxidase Inhibitors

“…Also published in 2004 were the synthesis and structure-activity of several 2-fluoro-4-chloro-5-substituted-phenyl pyrrole Protox herbicides, such as compound 84 [95]. This interesting pyrrole class of chemistry further extends the structureactivity of the 2-fluoro-4-chloro-5-substituted-phenylpyrazoles fluazolate (17) and pyraflufen-ethyl (18) discussed in Section 3.2.2 ( Fig.…”

“…ha À1 . The pyrazole 84 can be prepared in several steps starting from the 1,3-dipolar cycloaddition of 2-trifluoromethyl-3-methyl-1,3-oxazolium-5-olate 86 to 2-chloro-4-fluoro-5-ethynylphenol (85), followed by chlorination of the resulting pyrrole 87, and reaction of 88 with the corresponding bromo acetate [95] (Scheme 3.4).…”

Synthesis and Antimicrobial Activity of Pyrrolyl/Pyrazolyl Arylaminosulfonylmethyl 1,3,4-Oxadiazoles, 1,3,4-Thiadiazoles and 1,2,4-Triazoles

“…Amongst different heterocyclic systems, compounds having thiadiazole and triazole units displayed greater activity than those having oxadiazole units. The pyrrolyl/pyrazolyl-thiadiazoles and triazoles (7,8,13,14) showed greater activity than pyrrolyl/pyrazolyl-oxadiazoles (6,12). There is no marked difference in activity with compounds having pyrrolyl and pyrazolyl units.…”

“…3) Pyrazole nucleus has pronounced pharmacological applications as antianxiety, 4) antidiabetic, 5) antimicrobial, 6,7) herbicidal, 8) anti-inflammatory 9) and antibacterial. 10,11) Further, 1,3,4-oxadiazoles are very good bioisosteres of amides and esters which can contribute substantially in increasing pharmacological activity by participating in hydrogen bonding interactions with the receptors.…”

Design, Synthesis and Fungicidal Activities of Some Novel Pyrazole Derivatives

“…Compounds with pyrazole functional units exhibit antimicrobial [7], herbicidal [8], antitumor [9], insecticidal [10][11][12][13], fungicidal [14][15][16][17][18] and antiviral activities [19,20]. Lamberth [21] has summarized the significance of pyrazole derivatives in crop protection chemistry, including herbicidally-, fungicidally-and insecticidally-active pyrazole classes.…”