American Cyanamid herbicides

Another class of herbicides, the imida zolines, was discovered at American Cyanamid in the early 1980s. Extensive research has led to the development of four commercial compounds imazapyr, imazamethahenz-methyl, imazethapyr, and imazaquin (see Table 5). Like the sulfonylureas, the imidazolines are extremely active at low rates. 

SU and IM (Figure 1), are proprietary chemistry of DuPont (2.3) and American Cyanamid (4), respectively. The substituted 1,2,4-tria-zolo[l,5-a]pyrimidines (TP, Figure 1) are a new class of herbicides under development at Dow Chemical Co. (5). A number of reviews have already appeared on the biology and biochemistry of SU (6-10) and IM (1LJL2). Hence, the focus of this article has been on the work done at our premises on TP. Wherever appropriate, our results have been compared with those of SU and IM. 

Assignee American Cyanamide Company Utility Herbicide Intermediate... 

Heterocyclic aryl amines, such as pyridine and the pyrimidines, are important in the production of colorants and pharmaceutical products and, apart from mention in the relevant sections of this chapter, have received extensive reviews. Here the emphasis is on the industrial applications of aminotriazines, for which industrial interest followed the bulk commercial availability after 1945, particularly from American Cyanamid, of the chlorotriazine cyanuric chloride (182)96. Reactions of cyanuric chloride with amines and substituted amines afford substituted melamines and various aminotriazines that have found application in pharmaceuticals and herbicides. 

The workers at American Cyanamid present some of the synthetic and biological characteristics of the sulfur analogs of their imidazoline family of herbicides. This is an example of replacing the carbonyl of the imidazoli-none with an isosteric moiety. This is an interesting account of the synthesis and structure-activity relationships in a very active series of herbicides. 

Several 3-alkoxy- 4-methyl-6-phenylpyridazines, one of which is AC 247,909, have subsequently been disclosed as selective herbicides (JX)). A patent covering novel pyridazines and pyridazine N-oxides has been assigned to American Cyanamid (11). 

The imidazolinones are a new class of herbicides discovered and being developed by American Cyanamid Company. Previous papers in the imidazolinone area (1-12) have discussed the preparation and biological activity of various aryl substituted imidazolinones, in particular imazapyr 1 (AC 243,997, registered by American Cyanamid under the trademarks ARSENAL, ASSAULT and CHOPPER), imazethapyr 2 (AC 263,499, discovered and being developed by American Cyanamid under the trademark PURSUIT) and imazamethabenz 3/4 (AC 222,293, discovered and being developed by American Cyanamid under the trademark ASSERT). 

The phenylnitramines, 1, a class of plant growth regulators affecting root geotropism and shoot phototropism, was reported in 1954 by ICI (1). Twenty years later American Cyanamid(2) received patent for herbicidal phenylnitramines genetically represented by structure 2. Efficacy was dependent... 

The development of herbicide-resistant crop varieties as undertaken by American Cyanamid is an evolutionary process that proceeds through a series of decision points. Initially, the market potential for herbicide resistance in the crop is evaluated. After a project is assessed as worthwhile, a scheme to make the crop resistant is established and implemented. Once the scheme proves successful and resistance is introduced into the crop of interest, the trait is characterized to assess commercial utility. A method for delivering resistant crops to the marketplace is then identified. Finally, through close cooperation between the seed company and the chemical company, the herbicide-resistant crop becomes available commercially. 

This paper follows the evolution of the imidazolinone-resistant hybrid corn project at American Cyanamid. The initial considerations that provided the rationale for the project are discussed. The selection, regeneration, and characterization of the herbicide-resistant plants is described. Finally, options for commercializing the herbicide-hybrid package are discussed. 

In 1982, American Cyanamid began commercial development of the imidazolinone class of herbicides. These herbicides control a broad spectrum of economically important weeds in corn and soybeans. Although differences in tolerance of corn hybrids for imidazolinone herbicides exist (5), no hybrids with sufficient tolerance to allow application of current imidazolinone herbicides to corn fields have yet been identified. Other methods to supplement the inadequate levels of natural tolerance have likewise been ineffective. 

In this case, imidazolinone-resistant corn was identified through efforts initiated by a chemical company. Thus, American Cyanamid needed a cooperating party to supply herbicide-resistant hybrid seed to the farmer. Decisions on collaborators, rights to exclusivity, royalties, obligations, and deadlines all entered into the objective of achieving maximum market penetration in the shortest possible time period. 

Close coordination between the seed company and the chemical company is essential to assure that yield trials, efficacy trials, hybrid seed production, and the required herbicide label extensions proceed in a concerted fashion. The imidazolinone herbicide must be ready to be used when imidazolinone-resistant corn is ready for sale. Joint launch of the resistant hybrids and the herbicide label extension that includes resistant com will be coordinated by American Cyanamid and Pioneer Hi-Bred. 

Sales of a corn herbicide to be applied only to specifically labelled corn hybrids has never before been attempted. Marketing of this hybrid-herbicide package requires novel strategies for both American Cyanamid and Pioneer Hi-Bred. Farmer and dealer education about the package will be an integral part of insuring proper usage and customer satisfaction with product performance. 

Cyanuric chloride has three chlorine substituents and a stable aromatic triazine ring. Different substituents can be introduced onto the triazine because the chlorines have different reactivities. Cyanuric chloride is used in pesticides, herbicides, dyes, detergent brighteners, and so on [48], Cyanuric chloride also is used in the manufacture of hindered-phenol triazines as antioxidants for polyolefin resins. Cyanuric chloride production is more than 100,000 ton/yr [49]. American Cyanamid, Nilok, and Geigy are three U.S. producers of cyanuric chloride [50]. 

The imidazolinone herbicides (Table 2.3.1) are a family of six compounds that were discovered and developed by American Cyanamid Corporation. Readers may obtain comprehensive and detailed information in The Imidazolinone Herbicides [1], a book authored by the researchers who discovered and developed the herbicides. The herbicides as a class are broad spectrum and are active both pre-and postemergence. Imidazolinones are absorbed and moved through both xylem and phloem, eventually accumulating in the meristematic tissue. Activity is characterized by rapid cessation of growth followed by plant death days or weeks after treatment. Selectivity is based most often on metabolic inactivation except for selection-developed target site based resistance. 

Other ALS Inhibitors. A remarkable turn of agrichemical history is found in the independent discovery of the imidazolinone herbicides (also in Ae mid-1970 s) at American Cyanamid, and the subsequent finding that diese very active compounds also act solely through inhibition of ALS (12, Dow has announced that the... 

Dihydropyrano[2,3-b]pyridylimidazolinones and related compounds represent a new series in the imidazolinone herbicide family developed by American Cyanamid Company. The synthesis of the parent compound was accomplished by a novel enaminone-directed cyclization to the pyrano ring in the key step. These compounds showed excellent herbicidal activity with soybean selectivity. 

The intensive chemical synthesis program on the pyridylimid-azolinone herbicides at the Agricultural Research Division of American Cyanamid resulted in the discovery of several important crop protection products (1-7). Among them are 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid 1 (AC 243,997, imazapyr) and its isopropylamine salt 2 (AC 252,925) registered by American Cyanamid as ARSENAL, ASSAULT and CHOPPER total vegetation control herbicides. 

Introduction. Since their discovery, the imidazolinone herbicides have been the focus of much synthetic activity at American Cyanamid. This is due to their ability to control a broad spectrum of weeds at very low rates (e.g. 0.08-0.5 kg/Eia). The original discovery of the imidazolinone class of herbicides was described in detail by Los (1). His chapter describes the chemisny leading to tiie development of several compounds that are the active ingredients in commercial products. These include AC 222,293 (imazamethabenz) for control of mustard and wild oats in wheat, AC 243,997 (imazapyr), a total vegetation herbicide, and AC 252,214 (imazaquin), a broad spectrum herbicide for use in soybeans. An additional commercial compound AC 263,499 (imazethapyr) also used primarily for weed control in soybeans has been described (2). The satisfactory performance of these products has spurred interest in the discovery of other novel members of the imidazolinone class with good herbicidal properties. 

---