Carbamoyl tetrazolinones

Tetrazolinones were relatively unknown in herbicide chemistry until 1985, when Uniroyal Chemical applied for a patent describing the herbicidal action of carbamoyl tetrazolinones [21]. Several companies have explored this chemistry, and in 1999 Bayer CropScience launched the first practical tetrazolinone herbicide, Ten-trazamide, for grass control in rice (Fig. 8.5). 

Herbicidally active l-aryl-4-carbamoyl-tetrazolinones 304 were recently obtained by reacting 1-aryl-tetrazolinones with phosgene in the presence of a solvent at 0-150 °C, and then reacting the resulting (novel) l-aryl-4-chlorocarbonyl-tetrazolinones 303 with amines in the presence of a solvent, and, where appropriate, in the presence of a further basic compound, at —20 to +100 °C [234]. 

As shown in Fig. 8.6, the manufacturing processes of fentrazamide involve the conversion of two inexpensive run-of-the mill anilines, 2ethyl aniline, into 2-chlorophenyl isocyanate and Nsodium azide in the presence of catalytic amounts of aluminum trichloride in dimethyFormamide [25]. The tetrazolinone reacted with N-cyclohexyl-N-ethylcarbamoyl chloride, in the presence of a catalytic amount of 4-dimethylaminopyridine (DMAP), to afford fentrazamide with no formation of its O-carbamoylated isomer [26]. 

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