N- methylcarbamate

Other substituted phenyl A/-methylcarbamates that have been used for insect control include metalkamate [8065-36-9] a 1 4 mixture of y -(l-ethylpropyl)-phenyl A[-methylcarbamate [672-04-8] and y -(l-methylbutyl)-phenyl A/-methylcarbamate [2282-34-0], rat oral LD qS 87, 170 mg/kg, used as a soil insecticide MTMC [1129-41 -5], 3-methylphenyl N-methylcarbamate (mp 76°C), rat oral LD q 268 mg/kg, used for rice pests MPMC [2425-10-7], 3,5-dimethylphenyl A/-methylcarbamate (mp 79°C), rat oral LD q 380 mg/kg, used for rice pests TBPMC [780-11-0], 3-/ l -butylphenyl A/-methylcarbamate (mp 140°C), mouse oral LD q 470 mg/kg, for rice pests and butacarb [2655-19-8], 3,5-di-/ l -butylphenyl A/-methylcarbamate (mp 98°C), rat oral LD q >4000 mg/kg, for sheep blowfly larvae control. 

A 15.7 g (0.1 mol) of 2,6-dihydroxy methylpy rid in e hydrochloride are suspended in 176 ml of acetonitrile, and 20fi ml (0.15 mol) of triethylamine are added to the suspension. Thereafter 13 ml (0.22 mol) of methyl isocyanate are added dropwise to the reaction mixture at 20°C to 25°C. The reaction mixture is stirred at 20°C to 30°C for one hour, thereafter boiled for 3 hours, and finally the solvent is evaporated under reduced pressure. 35 to 40 g of a greyish, crystalline residue are obtained, which Is a mixture of 2,6-dihydroxymethylpyridine-bis-(N-methylcarbamate) and triethylamine hydrochloride. The obtained residue is dissolved in 80 ml of hot water, decolorized with 2 g of activated carbon when hot, and filtered after 30 minutes of stirring. The filtrate is cooled, the resulting crystal suspension is stirred at 0°C to 5°C for 3 hours, the solids are filtered off, and dried at 50°C to 60°C. 

Bj 23.3 g of 2,6-dihydroxymethylpyrldine-bis(N-methylcarbamate), prepared as described above, are dissolved in a boiling mixture of 46.6 ml of methanol and 46.6 ml of water. When the dissolution is complete, the solution is allowed to cool under slow stirring, without applying any external cooling means. The crystals start to separate at 48°C to 50°C. When the temperature of the mixture falls spontaneously below 35°C, it is cooled externally to 0°C to 5°C, and allowed to stand at this temperature for about 8 hours. Theseparated substance isfiltered off and dried at 50°C to 100°C. 22.65 g of 2,6-dihydroxymethylpyridine-bis(N-methylcarba-mate) are obtained. The quality of the product meets pharmaceutical requirements. 

The yield of this crystallization procedure is 95.7%. The above process provides the7j modification of 2,6-dihydroxymethylpyrldine-bis(N-methylcarbamate), which can be tabletted directly. The substance melts at 134°C to 1 36°C,its purity is99S% (determined by UV spectrophotometry). 

Multi-residue Method 2 Pesticides Analysed with HPLC Procedures, Submethod 1 N-methylcarbamate Pesticides, in Analytical Methods for Pesticide Residues in Foodstuffs, sixth edition. General Inspectorate for Health Protection, Ministry of Public Health, Welfare and Sport, The Hague, pp. 1-10 (1996). 

The widely used insecticide carbaryl (FD50=270 mg/kg) transforms in oxidizing processes into 5-oxynaphthyl-N-methylcarbamate, a substance that is as toxic as carbaryl itself (FD50=297 mg/kg) [30, 33]. One of the metabolites of the fungicide benomyl, the methyl ester carbamino acid (BMK, carbendazim), is also toxic to fungi [33]. 

N-methylcarbamate and N,N -dimethylcarbamates have been determined in soil samples by hydrolyses with sodium bicarbonate and the resulting amines reacted with 4-chloro-7-nitrobenzo-2,l,3-Oxadiazole in isobutyl methyl ketone solution to produce fluorescent derivatives [81]. These derivatives were separated by thin layer chromatography on silica gel G or alumina with tetrahydrofuran-chloroform (1 49) as solvent. The fluorescence is then measured in situ (excitation at 436 nm, emission at 528 and 537nm for the derivatives of methylamine and dimethylamine respectively). The... 

Metcalf, R.L., Fukuto, T.R., Collins, C., Borck, K., AbdEl-Aziz, S., Munoz, R., and Cassil, C.C. Metabolism of 2,2-dimethyl-2,3-dihydrobenzofuranyl-7 n-methylcarbamate (furadan) in plants, insects, and mammals, 7 Agric. RborfCAem., 16(2) 300-311, 1968. 

Pesticides organophosphates, N-methylcarbamates, benzimidazoles, azoles, ureas,... 

Figure 2. Equations showing the reaction between an JN-chlorosul-fenyl-IJ-methy 1 carbamate intermediate (or corresponding I -chloro-sulfinyl-N-methylcarbamate) and different nucleophilic agents.

More recently, an interesting reaction was discovered which provides the means for the synthesis of a wide variety of methylcarbamate derivatives containing the N-sulfinyl [N-S(O)] moiety (34). In attempting to prepare isopropoxy-N-methyliminoyl chloride by the reaction between Isopropyl methylcarbamate and thionyl chloride, an unexpected product, isopropyl ll-chloro-sulfinyl-N-methylcarbamate was obtained according to the equation below. The same product also was obtained when the... 

Drevenkar V, Stengl B, Tkalcevic B, et al. 1983. Occupational exposure control by simultaneous determination of N-methylcarbamates and organophosphorus pesticide residues in human urine. Int J Environ Anal Chem 14 215-230. 

Substituted phenyl N-methylcarbamates (ArOCONHMe) are one of the most widely used agricultural insecticide classes which inhibit acetylcholinesterase (AChE). The steps by which they react with AChE are shown in Eq. 13, where EOH denotes the enzyme. 

Fig. 2. Two reaction pathways of phenyl N-methylcarbamates with acetylcholinesterase the boldfaced arrow indicates an electron pair migration as the driving force of the reaction14) (reproduced with permission from Academic Press, Inc.)...

Nondek et al. (46) reported an innovative approach to the analysis of N-methylcarbamates in river water using postcolumn reaction detection. Separation of the underivatized N-methylcarbamates was carried out on a reversed-phase column hooked directly to a bed reactor packed with Aminex A-28, a tetraalkylammonium anion-exchange resin. The packed bed catalytically base-hydrolyzed the carbamates and... 

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