Oxime-N-methylcarbamates

Carbamates are substituted esters of carbamic acid (NH2COOH) with aliphatic or aromatic substituents on the oxygen and nitrogen atoms. Carbamate insecticides have an aryl or oxime N-methylcarbamate structure, and their mode of action is based on the inhibition of the enzyme acethylcholine esterase (1). However, this inhibition is reversible, and recovery from sublethal doses occurs rapidly. Some carbamate fungicides have a dithio, bisdithio, or benzimidazole carbamate basic structure, and dithiocarbamate fungicides inhibit the enzyme aldehyde deshydro-genase (2). The herbicides have an /V-alkylthiocarbamate or A-phenylcarbamate structure and interfere with photosynthetic activity or affect meristematic activity or lipid metabolism (3). Representative structures of carbamate pesticides are shown in Fig. 1. 

Rosenfeld and Kilsheimer (1974) prepared several 2,2,2-trifluoroacetophenone oxime methylcarbamates substituted on the ring. Among these, o-methoxy-2,2,2-trifluoroacetophenone oxime N-methylcarbamate (54) and o-fluoro-2,2,2-tri-fluoroacetophenone oxime N-methylcarbamate (55) are the most efficient. Their insecticidal action is nearly identical to that of carbaryl (3), white their cholinesterase-inhibiting effect surpasses substantially that of carbaryl. 

Carbamate Insecticides. These are structurally optimized derivatives of the unique plant alkaloid physostigmine [57-47-6], a cholinergic drug isolated in 1864 from Physostigma venenosum (see Alkaloids) (17,24,35—39). The carbamates maybe considered synthetic derivatives of the synaptic neurotransmitter acetylcholine, with very low turnover numbers. The N,N-dimethylcarbamates of heterocyclic enols (36) and the N-methylcarbamates of a variety of substituted phenols (35) with a wide range of insecticidal activity were described in 1954 (35). The latter are the most widely used carbamate insecticides, and the N-methylcarbamates of oximes have subsequently been found to be effective systemic insecticides. 

Miles and Moye [171] have shown that several classes of nitrogen containing pesticides responded to a high performance liquid chromatography post-column reaction detector that employed ultraviolet photolysis with optional reaction with o-phthalicdicarboxaldehyde-2-mercaptoethanol followed by fluorescence detection. It was applied to the determination of N-methylcarbamates, carbamoyl oximes, carbamethoic acids, dithiocarbamates and phenyl ureas, phenyl amides and phenyl carbamates in groimdwater. See also Table 4.3. 

Synonyms 1 -(methylthio)ethylideneamino methylcarbamate thio-A- ((methylearba-moy)oxy)acetimidie acid methyl ester 1 - (methylthio)acetaldehyde- O-methyIcar-bamoyl oxime methylacetimidothioic acid iV-(methylcarbamoyl) ester methyl N-((methylcarbamoyl)oxy)thioacetimidate Lannate Mesomule DuPont 1179. 

Andrawes, N.R., W.P. Bagley, and R.A. Hemett. Fate and Carryover Properties of Temik Aldicarb Pesticide [2-Methyl-2-(methylthio)propionaldehyde 0-(methylcarbam-oyl)oxime] in Soil, J. Agric. Food Chem., 19(4) 727-730 (1971). 

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