Fungicides 1,3,4-thiadiazoles

Thiadiazoles have found applications as pharmaceuticals, fungicides, herbicides, bacteriocides, dyes, lubricant additives, and vulcanization accelerators. Cephalosporins incorporating a 1,2,4-thiadiazole ring into the side chain have good antibiotic and antimicrobial properties. 

Ethoxy-3-trichloromethyl-l,2,4-thiadiazole has excellent pesticidal and fungicidal properties. It is a commercial product, whose most common trade name is Terrazole. 

Whereas 5-triazolo[3,4-fe][l,3,4]thiadiazoles (l,2,4-triazolo[3,4-6][l,3,4j thiadiazoles, 190) are reported repeatedly, especially with respect to their fungicidal and bactericidal activity, the corresponding isomeric 1,2,4-tria-zolo[5,l-6][l,3,4]thiadiazol system 191 has been investigated far less intensively. 

The excellent pesticidal and fungicidal properties of 5-ethoxy-3-trichloromethyl-1,2,4-thiadiazole (363) are well known <82AHC(32)285). It is a commercial product and is marketed under a variety of names of which Terrazole is the most common. Since 1984, a variety of 1,2,4-thiadiazole derivatives have been found to possess fungicidal activity. Thus, compounds such as (364), (365), and (366) and... 

A commercial soil or seed treatment fungicide, 5-ethoxy-3-tfichloromethyl-l,2,4-thiadiazole [2593-15-9] (etridiazole) is prepared from 2-chloro-3-tfichloromethyl-l,2,4-thiadiazole [5848-93-17, a product of tfichloromethanesulfenyl chloride and trichloroacetamidine (68). 

Fungicidal properties are exhibited by 3-methyl-209 and 3-methyl-thio-5-arylsulfonyl-l,2,4-thiadiazoles,210 5-substituted 3-trichloro-methyl-1,2,4-thiadiazoles,97 2,4-dimethyl-3-thiono-l,2,4-thiadiazoli-din-5-one,164,166,211 and 2,4-dimethyl-l,2,4-thiadiazolidine-3,5-dithi-one.165,166 5-Halogeno-3-halogenoalkyl-l,2,4-thiadiazoles are active against Rhizoctonia aolani,9B... 

The fungicidal properties212 and production of albinism in plants213 that have been referred to in connection with two 1,2,4-thiadiazoles are actually properties of the corresponding 1,3,4-isomers.214... 

Chemical Name 5-ethoxy-3-(trichloromethyl)-l,2,4-thiadiazole ethyl 3-trichloromethyl-l,2,4-thiadiazolyl ether Uses as fungicide for control of Phytophthora and Pythium spp. in cotton, ornamentals, vegetables, groundnuts, cucurbits, tomatoes, and other crops also used as a nitrification inhibitor in maize, cotton and wheat. 

The pyridine compounds used as plant growth regulators include 1 //-pyrrolo[2,3b]pyridinc-3-acetic acid 69 <2004BPC247> and 2-amino-5[(2-chloropyrid)-4-yl]-l,3,4-thiadiazole 70 <2002YH795>, with the latter compound having additional fungicidal activity. 

During the past 15 years numerous patents have issued on the synthesis and use of 1,2,4-thiadiazoles as fungicides, herbicides, insecticides, bactericides, dyes, lubricant additives and vulcanization accelerators. The largest number of patents appear to be concerned with fungicides. ... 

Trifluoroacetic acid or trifluoroacetic acid anhydride reacts with hydrox-amic acid amides, thiosemicarbazide, and 1,2-diaminopyridine to yield herbicidal active 1,2,4-oxadiazoles [78GEP(0)2801509], fungicidal-active 1,3,4-thiadiazoles (80USP4264616), and 2-trifluoromethyltriazolo[l,5-alpyridines [80JFC(15)179. 2-Trifluoromethyl-L-histidine was obtained from L-histidine on treatment with benzoyl chloride/sodium hydroxide and subsequent ring closure with trifluoroacetic anhydride (78JOC3403) (Scheme 41). 

Etridiazole, 5-cthoxy-3-trichloromethyl-l,2,4-thiadiazole (73), is an efficient soil fungicide with systemic action. 

Reports are available of the screening of 1,2,4-thiadiazoles459 460 as systemic insecticides. 5-Alkoxy-3-trichloromethyl-1,2,4-thiadiazoles, the proved fungicides, have also insecticidal and acaricidal properties.461 1,2,4-Thiadia-zoles may act as chemosterilants462 5-amino-3-methyl(or methylthio)-1,2,4-thiadiazole are found to have this action in the housefly.463,464 5-Chloro-3-ethylthio-1,2,4-thiadiazole has nematocidal activity.465... 

The preparation of 5-ethoxy-3-trichloromethyl-l,2,4-thiadiazole was first reported3,471 in 1962, and its excellent pesticidal properties publicized shortly afterwards 472 Since then its effectiveness and usefulness as a systemic soil fungicide have been proved in a large number of trials. It has become firmly established in agricultural practice, and is known under a variety of commercial names,473,474 Terrazole being the most common. Numerous... 

For many [l,2,4]triazolo[3,4-6][l,3,4]thiadiazoles (170) both fungicidal and herbicu have been found (Table 16). ... 

Although the 1,2,4-thiazole moiety does not occur in natural products, many synthetic derivatives are biologically active and are used as insecticides, fungicides, herbicides and antibacterials. For instance, 5-ethoxy-3-trichloromethyl-l,2,4-thiadiazole (etridiazole) is used to combat or prevent fungal infestation of plants, fruit, cotton, seeds and soil [149]. 

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