Butafenacil is the

ISO The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. Me ...

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...

for an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

of the

pyrimidinedione Pyrimidinediones are a class of chemical compounds characterized by a pyrimidine ring substituted with two carbonyl groups. Examples include naturally occurring metabolites: drugs: * Fluorouracil * Idoxuridine * Primidone Primidone, sold ...

chemical class used as an

herbicide Herbicides (, ), also commonly known as weed killers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page f ...

. It acts by inhibiting the enzyme

protoporphyrinogen oxidase Protoporphyrinogen oxidase or protox is an enzyme that in humans is encoded by the ''PPOX'' gene. Protoporphyrinogen oxidase is responsible for the seventh step in biosynthesis of protoporphyrin IX. This porphyrin is the precursor to hemoglobin, ...

to control broadleaf and some grass weeds in crops including

cereals A cereal is a grass cultivated for its edible grain. Cereals are the world's largest crops, and are therefore staple foods. They include rice, wheat, rye, oats, barley, millet, and maize (Corn). Edible grains from other plant families, suc ...

and

canola file:CanolaBlooms.JPG, Close-up of canola blooms file:Canola Flower.jpg, Canola flower Rapeseed oil is one of the oldest known vegetable oils. There are both Edible oil, edible and industrial forms produced from rapeseed, the seed of several ...

History

In 1985, chemists at the Dr. R. Maag subsidiary of

Hoffmann-La Roche F. Hoffmann-La Roche AG, commonly known as Roche (), is a Swiss multinational holding healthcare company that operates worldwide under two divisions: Pharmaceuticals and Diagnostics. Its holding company, Roche Holding AG, has shares listed on ...

filed patents for

uracil Uracil () (nucleoside#List of nucleosides and corresponding nucleobases, symbol U or Ura) is one of the four nucleotide bases in the nucleic acid RNA. The others are adenine (A), cytosine (C), and guanine (G). In RNA, uracil binds to adenine via ...

derivatives which had herbicidal activity. In 1990 the agrochemical interests of Maag were sold to

Ciba-Geigy Novartis AG is a Swiss multinational pharmaceutical corporation based in Basel, Switzerland. Novartis is one of the largest pharmaceutical companies in the world and was the eighth largest by revenue in 2024. Novartis manufactures the drugs ...

and work continued to optimise this area of

biological activity In pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or ...

. By 1993 a patent claiming specific

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

derivatives including butafenacil was published. This was developed for the market under the code number CGA276854 and launched in 2001. By that time, further mergers in the industry meant that the product was supplied by

Syngenta Syngenta Global AG is a global agricultural technology company headquartered in Basel, Switzerland. It primarily covers crop protection and seeds for farmers. Syngenta is part of the Syngenta Group, entirely owned by Sinochem, a Chinese state ...

with

brand name A brand is a name, term, design, symbol or any other feature that distinguishes one seller's goods or service from those of other sellers. Brands are used in business, marketing, and advertising for recognition and, importantly, to create and ...

s including B Power.

Synthesis

As described in the Ciba-Geigy patent, the key step in the preparation of butafenacil involved the reaction between a phenyl

isocyanate In organic chemistry, isocyanate is the functional group with the formula . Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyan ...

and an

amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...

. Ethyl 2-chloro-5-isocyanato-benzoate and ethyl 3-amino-4,4,4-trifluorocrotonate were reacted in the presence of a base to form a substituted

urea Urea, also called carbamide (because it is a diamide of carbonic acid), is an organic compound with chemical formula . This amide has two Amine, amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest am ...

intermediate which was cyclised to the pyrimidinedione, as shown. Further standard chemical transformations generated the final product.

Mechanism of action

Butafenacil works by inhibiting protoporphyrinogen IX oxidase (PPO), preventing

chlorophyll Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words (, "pale green") and (, "leaf"). Chlorophyll allows plants to absorb energy ...

formation, and resulting in the accumulation of

protoporphyrin IX Protoporphyrin IX is an organic compound, classified as a porphyrin, that plays an important role in living organisms as a precursor to other critical compounds like heme (hemoglobin) and chlorophyll. It is a deeply colored solid that is not sol ...

which is a potent

photosensitizer Photosensitizers are light absorbers that alter the course of a photochemical reaction. They usually are catalysts. They can function by many mechanisms; sometimes they abstract an electron from the substrate, and sometimes they abstract a hydro ...

. This activates oxygen, causing lipid peroxidation with rapid loss of membrane integrity and function. The effects visible on whole plants are

chlorosis In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

and

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. The term "necrosis" came about in the mid-19th century and is commonly attributed to German pathologist Rudolf Virchow, who i ...

. Butafenacil's HRAC herbicide resistance class is Group G, (Aus), E (Global), 14 (Numeric).

Usage

Butafenacil is registered for use in

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

, Argentina, Brazil, Japan, and Thailand but not now in the

European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...

or USA, although it was conditionally given approval there in 2003. The herbicide controls annual and perennial broadleaf weeds and some grasses. It has little selectivity so is usually applied before sowing crop seeds. It is effective post-emergence on a very wide range of species including ''

Arctotheca calendula ''Arctotheca calendula'' is a plant in the sunflower family commonly known as capeweed, plain treasureflower, cape dandelion, or cape marigold because it occurs in the Western Cape Province in South Africa. It has a wide distribution in coastal ...

'', ''

Avena fatua ''Avena fatua'' is a species of grass in the oat genus. It is known as the common wild oat. This oat is native to Eurasia but it has been introduced to most of the other temperate regions of the world. It is naturalized in some areas and consi ...

'', ''

Bidens pilosa ''Bidens pilosa'' is an annual species of herbaceous flowering plant in the daisy family Asteraceae. Its many common names include hitch hikers, black-jack, beggarticks, farmer's friends and Spanish needle, but most commonly referred to as co ...

'', ''

Boerhavia diffusa ''Boerhavia diffusa'' is a species of flowering plant in the Nyctaginaceae, four o'clock family which is commonly known as punarnava (meaning that which rejuvenates or renews the body in Ayurveda), red spiderling, spreading hogweed, or tarvine. I ...

'', ''

Brassica napus Rapeseed (''Brassica napus'' subsp. ''napus''), also known as rape and oilseed rape and canola, is a bright-yellow flowering member of the family Brassicaceae (mustard or cabbage family), cultivated mainly for its oil-rich seed, which naturall ...

'', ''

Brassica tournefortii ''Brassica tournefortii'' is a species of plant known by the common names Asian mustard, pale cabbage, African mustard, Sahara mustard, and Aslooz. ''Brassica tournefortii'' is also used in North African cuisine. In Libya, it is known as Asloo ...

'', '' Bromus diandrus'', ''

Capsella bursa-pastoris ''Capsella bursa-pastoris'', known as shepherd's purse or lady's purse because of its triangular flat fruits, which are purse-like, is a small annual and ruderal flowering plant in the mustard family (Brassicaceae). Scientists have referred to ...

'', ''

Carthamus lanatus ''Carthamus lanatus'' is a species of thistle known as woolly distaff thistle, downy safflower or saffron thistle. It is closely related to safflower (''Carthamus tinctorius''). This annual plant is a native of the Mediterranean Basin, but it is ...

'', ''

Chenopodium album ''Chenopodium album'' is a fast-growing annual plant in the flowering plant family Amaranthaceae. Though cultivated in some regions, the plant is elsewhere considered a weed. Common names include lamb's quarters, melde, goosefoot, wild spinach a ...

'', '' Chenopodium pumilio'', ''

Cirsium acaule ''Cirsium acaule'' or ''acaulon'' has the English name dwarf thistle or stemless thistle. It is widespread across much of Europe.

'', ''

Echinochloa crus-galli ''Echinochloa crus-galli'' is a type of wild grass originating from tropical Asia that was formerly classified as a type of panicum grass. It is commonly known as cockspur (or cockspur grass), barnyard millet, Japanese millet, water grass, commo ...

'', ''

Emex australis ''Rumex hypogaeus'' (synonym ''Emex australis''), commonly known in English as southern threecornerjack, devil's thorn, or double gee (also doublegee, from the old Afrikaner name dubbeltge-doorn - 'double thorned'), is a herbaceous plant of the ...

'', '' Erodium botrys'', ''

Erodium cicutarium ''Erodium cicutarium'', also known as common stork's-bill, redstem filaree, redstem stork's bill or pinweed, is a herbaceous annual plant, annual – or in warm climates, biennial plant, biennial – member of the family Geraniaceae of flowering ...

'', ''

Festuca arundinacea ''Lolium arundinaceum'', commonly known as tall fescue, is a cool-season, perennial C3 grass species native to Europe and introduced to North America and other parts of the world. It naturally occurs in grasslands and coastal marshes.Texas Park ...

'', '' Hordeum leporinum'', ''

Hypochaeris radicata ''Hypochaeris radicata'' (sometimes spelled ''Hypochoeris radicata'') – also known as catsear, flatweed, cat's-ear, hairy cat's ear, or false Taraxacum, dandelion – is a perennial plant, perennial, low-lying edible herb often found in lawns. ...

'', ''

Lamium amplexicaule ''Lamium amplexicaule'', commonly known as henbit dead-nettle, is a species of ''Lamium'' native to most of Europe, Asia and northern Africa. The specific name (botany), specific name refers to the leaves, which are Amplexicaul leaf, amplexicaul ...

'', ''

Lolium rigidum ''Lolium rigidum'' is a species of annual grass. Common names by which it is known include annual ryegrass, a name also given to Italian ryegrass (''Lolium multiflorum''), rigid ryegrass, stiff darnel, Swiss ryegrass and Wimmera ryegrass. It is ...

'', ''

Lupinus angustifolius ''Lupinus angustifolius'' is a species of lupin known by many common names, including narrowleaf lupin, narrow-leaved lupin and blue lupin. It is native to Eurasia and northern Africa and naturalized in parts of Australia and North America. It h ...

'', ''

Malva parviflora ''Malva parviflora'' is an annual or perennial herb that is native to Northern Africa, Southern Europe, and Western and Central Asia and is widely naturalized elsewhere. Common names include cheeseweed, cheeseweed mallow, Egyptian mallow, least ...

'', ''

Medicago sativa Alfalfa () (''Medicago sativa''), also called lucerne, is a perennial flowering plant in the legume family Fabaceae. It is cultivated as an important forage crop in many countries around the world. It is used for grazing, hay, and silage, as we ...

'', ''

Modiola caroliniana ''Modiola'' is a monotypic genus of plants in the mallow family containing the single species ''Modiola caroliniana'', which is known by several common names including bristly-fruited mallow, Carolina bristlemallow, babosilla, and redflower mall ...

'', ''

Panicum capillare ''Panicum capillare'', known by the common name witchgrass, is a species of grass. It is a native plant to most of North America from the East Coast through all of the West Coast and California. It can be found as an introduced species in Eur ...

'', ''

Panicum effusum ''Panicum effusum'', commonly known as hairy panic, is a grass native to inland Australia. It occurs in every mainland state, as well as New Guinea. In dry conditions, the fast-growing grass can become a tumbleweed. Description Hairy panic is a ...

'', ''

Phalaris paradoxa ''Phalaris paradoxa'' is a species of grass in genus ''Phalaris''. Common names include awned canary-grass and hood canarygrass. The spikelets are very different from those of other members of this genus. The spikelet glumes each have a hook. ...

'', ''

Polygonum aviculare ''Polygonum aviculare'' or common knotgrass is a plant related to buckwheat and dock. It is also called prostrate knotweed, birdweed, pigweed and lowgrass. It is an annual found in fields and wasteland, with white flowers from June to October. I ...

'', ''

Portulaca oleracea ''Portulaca oleracea'' (common purslane, also known as little hogweed, or pursley) is a succulent plant in the family Portulacaceae. Description The plant may reach in height. It has smooth, reddish, mostly prostrate stems, and the leaves, w ...

'', ''

Raphanus raphanistrum ''Raphanus raphanistrum'', also known as wild radish, white charlock or jointed charlock, is a flowering plant in the family Brassicaceae. The species is native to western Asia, Europe and parts of Northern Africa. It has been introduced into mo ...

'', '' Rapistrum rugosum'', ''

Rumex acetosella ''Rumex acetosella'', commonly known as red sorrel, sheep's sorrel, field sorrel and sour weed, is a species of flowering plant in the buckwheat family Polygonaceae. Native to Eurasia including the British Isles, the plant and its subspecies are ...

'', ''

Rumex crispus ''Rumex crispus'', the curly dock, curled dock or yellow dock, is a perennial plant, perennial flowering plant in the family Polygonaceae, native to Europe and Western Asia. Description The plant produces an inflorescence or flower stalk that ...

'', '' Salvia reflexa'', '' Sisymbrium orientale'', ''

Sonchus oleraceus ''Sonchus oleraceus'' is a species of flowering plant in the tribe Cichorieae of the family Asteraceae, native species, native to Europe and Western Asia. It has many common names including common sowthistle, sow thistle, smooth sow thistle, annu ...

'', ''

Tribulus terrestris ''Tribulus terrestris'' is an annual plant in the caltrop family (Zygophyllaceae) widely distributed around the world. It is adapted to thrive in dry climate locations in which few other plants can survive. It is native to warm temperate and t ...

'', ''

Urochloa panicoides ''Urochloa panicoides'' is a fodder grass originating in Southern Africa. Description This annual grass has decumbent or upright stems up to a meter long. It may root where its lower nodes contact the substrate. The leaves have linear or lance- ...

'', ''

Urtica urens ''Urtica urens'', commonly known as annual nettle, dwarf nettle, small nettle, dog nettle, or burning nettle, is a herbaceous annual flowering plant species in the nettle family Urticaceae. It is native to Eurasia, including the Himalayan regions ...

'', ''

Vicia sativa ''Vicia sativa'', known as the common vetch, garden vetch, tare or simply vetch, is a Nitrogen fixation, nitrogen-fixing legume, leguminous plant in the family Fabaceae. It is now naturalised throughout the world occurring on every continent, exc ...

'' and ''

Vulpia bromoides ''Vulpia bromoides'', squirreltail fescue, barren fescue or brome fescue, is a species of grass in the family Poaceae Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants com ...

''. The product is typically used at application rates of 10 g a.i. per hectare, often in combination with other herbicides such as

paraquat Paraquat ( trivial name; ), or ''N'',''N''′-dimethyl-4,4′-bipyridinium dichloride (systematic name), also known as methyl viologen, is a toxic organic compound with the chemical formula C6H7N)2l2. It is classified as a viologen, a family o ...

and

glyphosate Glyphosate (IUPAC name: ''N''-(phosphonomethyl)glycine) is a broad-spectrum systemic herbicide and crop desiccant. It is an organophosphorus compound, specifically a phosphonate, which acts by EPSP inhibitor, inhibiting the plant enzyme 5-en ...

in direct drilling of cereals and canola.

Human safety

The LD₅₀ of butafenacil is over 5000 mg/kg (rats, oral), which means that it is of low toxicity by oral ingestion. The toxicity of protoporphyrinogen oxidase inhibitors has been reviewed.

References

{{herbicides PPO herbicides Pyrimidinediones Trifluoromethyl compounds Chloroarenes Group 14 herbicides