2.2- Dichlorovinyl compounds

Dichlorovinyl compounds from acetic acids 611 OGH2GgH5... 

From a-trichloromethyl carbinols with the hydroxy group at a tertiary carbon, either dichlorovinyl compounds or, after rearrangement, carbonyl compounds are formed predominantly. The pathway of the reaction can be influenced by the choice of the reaction conditions. As the reduction potentials of some of the substrates are... 

Variations in the reaction temperature and in the proportions of the ketone and PCI5 were appreciably reflected in the ratio of the amounts of compound 9 obtained in the first stage to the total content of 7 and 8 and then proportionally in the composition of the final products. In the interaction of the ketones with PCI5, an excess of the latter and high temperature make the anomalous reactions more significant. 4-(l,2-Dichlorovinyl)-3,5-dimethyl-l//-pyrazole (9) was obtained individually by the action of more than a twofold excess of PCI5 on the acetylpyrazole 6 at 80°C in 50% yield. Under the influence of NaNHa in liquid NH3, dichloroethy-lene 9 was converted into chloroacetylene 10 by loss of a molecule of HCl (yield 77%) (Scheme 28). 

Although trichloroethylene itself may not be genotoxic, several of its metabolites are reactive and potentially genotoxic compounds (Miller and Guengerich 1982). Several isomers of 1,2-dichlorovinyl-cysteine, a product of trichloroethylene metabolism in the kidney, are mutagenic in the in vitro Ames assay... 

Transfluthrin (30) [39] is a compound obtained by esterification of dichlorovinyl chrysanthemic acid with 2,3,5,6-tetrafluolobenzylalcohol. With very high insecticidal potency against mosquitoes and flies, it is used as a household insecticide however, as the promotion activity of the compound is known, its use should be restricted to preparations in which the issues of safety for humans and pets have been resolved. 

Mattson, A.M., Spillane, J.T., and Pearce, G.W. Dimethyl 2,2-dichlorovinyl phosphate (DDVP), an organic phosphorus compound highly toxic to insects, J. Agric. Food Chem., 3(4) 319-321, 1955. 

These subsequent metabolic transformations are known to be involved in the nephrotoxicity of a number of compounds such as S-(l,2-dichlorovinyl)-L cysteine and hexachlorobu-tadiene (see chap. 7). Thus, although the initial glutathione conjugation may be a detoxication step, the final product of this phase 3 reaction may prove to be toxic. 

Trichloroethylene is metabolized similarly and gives rise to dichlorovinyl cysteine. It has been found that S-(l,2-dichlorovinyl)-L-cysteine (DCVC) and S-(2-chloroethyl)-DL-cysteine (CEC) (Fig. 7.30) are both nephrotoxic when administered to animals causing renal proximal tubular necrosis. CEC does not require 3-lyase activation to be nephrotoxic, but can rearrange, possibly to a reactive episulfonium ion, by nucleophilic displacement of the chlorine atom. These compounds decrease the activity of the renal tubular anion and cation transport system. 

The effect of these resistances has been to drive chemical control from one insecticide to the next. In most parts of the Nile delta the cotton leafworms can still be controlled by some OP compound, such as chlorpyrifos, supplemented where necessary with the insect growth regulator Dimilin. But in southern Texas, Mexico, Nicaragua and Peru the multiple resistances of the tobacco budworm, and to a less extreme degree of H. zea and Spodoptera sunia, have made even 20 insecticide applications a season quite worthless, and indeed there is less damage to the cotton if no chemicals are applied at all. The only materials that can be relied upon to kill these multiresistant H. viresoens are the dichlorovinyl pyrethroid NRDC-143 and the Heliothis nuclear polyhedrosis virus. 

Vinyliodonium ions, 35 and 36, are hypervalent iodine species in which one or two alkenyl ligands are bound to a positively charged iodine(III) atom. Although they are reactive with nucleophilic reagents, they are less labile than alkynyliodonium ions, and stable halide salts of vinyliodonium ions can be prepared. The first vinyliodonium compounds [i.e. (a, / -dichlorovinyl)iodonium salts] were synthesized by the treatment of silver acetylide-silver chloride complexes with (dichloroiodo)arenes or l-(dichloroiodo)-2-chloroethene in the presence of water (equation 152). The early work was summarized by Willgerodt in 1914115. This is, of course, a limited and rather impractical synthetic method, and some time elapsed before the chemistry of vinyliodonium salts was developed. Contemporary synthetic approaches to vinyliodonium compounds include the treatment of (1) vinylsilanes and vinylstannanes with 23-iodanes, (2) terminal alkynes with x3-iodanes, (3) alkynyliodonium salts with nucleophilic reagents and (4) alkynyliodonium salts with dienes. 

FIGURE 57.8. Spectrum of log values of relative inhibitory potency (RIP) = 7i(AChE)/ i(NTE), where = himolecular rate constant of inhibition. As log(RIP) becomes more positive, cholinergic potential increases as log(RIP) becomes more negative, delayed neuropathic potential increases. CPMO-chlorpyrifos methyl oxon. DCV derivatives refer to symmetrical dialkyl-2,2-dichlorovinyl phosphate (dichlorvos) compounds. EOPF - ethyl n-octylphosphonofluoridate. Data from Kropp and Richardson (2003) Richardson (1992) and Wu and Casida (1996). 

In general, arsenical compounds have an aggressive action when two of the three valences of the arsenic atom are linked to like atoms or groups and the third to a different atom or radicle. If all the three valences of the arsenic atom are linked to similar atoms or radicles the compound has practically no aggressive action. Thus in the series of chlorovinyl arsines, it has been found that trichlorovinyl arsine has practically no aggressive action compared with chlorovinylchloroarsine or dichlorovinyl chloroarsine ... 

They have high boiling points (190° to 260° C.), but on heating at ordinary pressure easily decompose. Chlorovinyl dichloroarsine is thus decomposed into dichlorovinyl chloroarsine and arsenic trichloride, dichlorovinyl chloroarsine into chlorovinyl dichloroarsine and acetylene, etc. This behaviour supports the belief that an equilibrium exists between the three chlorovinyl arsines and their components, acetylene and arsenic trichloride. The hypothesis is confirmed by the observation that from the reaction between acetylene and arsenic trichloride, it is not possible to produce any one of these compounds solely a mixture of all three is always obtained. 

Nitric Acid. By the action of concentrated nitric acid on /3/3 dichlorovinyl chloroarsine a crystalline product is obtained which melts at 97° to 99° C. this is the nitrate of )8)8 dichlorovinyl arsenic acid (ClCH=CH)2As00H.HN03. This compound apparently does not ionise in solution, but when dissolved in aqueous alcohol and treated with sodium hydroxide solution until the nitric acid is neutralised, decomposition takes place. On extracting with chloroform and evaporating the extract, a crystalline mass remains which consists of dichlorovinyl arsenic acid (Mann and Pope), (CHCl=CH)2AsOOH. This is purified by recrystallisation from water or carbon tetrachloride, when it melts at 120° to 122° C. Like cacodylic acid, it is amphoteric, forming salts with acids as well as with bases. 

Chloramine-T. Treatment of dichlorovinyl chloroarsine with an equivalent amount of chloramine-T (CHa=C H4—S02Na=NCl) produces no additive-compound, unlike trichlorovinyl arsine. 

Similarly, Neufeld et al. reported the fabrication of rapid amperometric micro flow injection electrochemical biosensor for the detection of highly toxic OP compound, 2, 2-dichlorovinyl phosphate (DDVP) [4], Here, the detection was done by monitoring the inhibition of enzymatic reaction by DDVP. The reduction of [Fe(CN)6]"3 to [Fe(CN)6]4 followed by the reaction with thiocholine in the working solution generates sharp, rapid and reproducible electric signals. The net reaction is explained in (2) and (3). 

Chemical and Physical Properties Trichlorfon is an organophosphate compound, which has an empirical formula of C4HgCl304P and a molecular weight of 257.44. It is a racemic mixture of two isomers. Trichlorfon is a pale clear, white or yellow crystalline powder, melting point 75-84°C, boiling point 100°C, vapor pressure 7.8mmHg at 20°C, and is stable at normal temperatures and pressure. At higher temperatures and pH less than 5.5, trichlorfon decomposes to form dichlorvos (0,0-dimethyl-0-(2,2-dichlorovinyl) phosphate, DDVP). It is readily soluble in chloroform and methylene chloride, and less soluble in water, benzene, and diethyl ether. 

Vapona [Shell], TM for an insecticide that contains more than 93% 2,2-dichlorovinyl dimethyl phosphate and less than 7% active, related compounds. 

In this work it was reported that the biological activity and residual properties of biphenyl-3-ylmethyl (1R,S)-cis-3-(2,2-di-chlorovinyl)-2,2-dimethylcyclopropanecarboxylate were about one-half that of the corresponding 3-phenoxybenzyl ester. The preparation of a series of substituted derivatives of biphenyl-3-ylmethyl (1R,S)-cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-carboxylates resulted in esters with significantly greater insecticidal activity and broader spectrum of biological activity than the conventional pyrethroid insecticides(7). The 2-monosubstituted derivatives were found to be the most active compounds in this series with the 2-methyl compound being the most active. This result encouraged us to combine these biphenyl-3-ylmethyl compounds with alkyl aryl methanone oximes. 

Between 1948 and 1952 Morris and Van Winkle (1952), Arbuzov and Alimov (1951), and Perkow et al. (1952) investigated independently the reaction of polyhalogen aldehydes, primarily of chloral, with trialkyl phosphites. The conversion was assumed by some workers to be a true Michaelis-Arbuzov reaction and, accordingly, it was thought erroneously that the product formed in the reaction of chloral and trimethyl phosphite is the phosphonate of formula 66. Perkow et al. (1952) established that a-halogen carbonyl compounds give with trialkyl phosphites an anomalous Michaelis-Arbuzov reaction, so that the actual reaction product is 2,2-dichlorovinyl phosphate, 67. This reaction is known in the literature as Perkow s reaction. 

The chain terminal dichlorovinyl group of compounds 36 and 45 resulted in enhanced field stability as compared with the epoxidised analogues. 

Metrifonate (trichloifon bearcil) is an organophosphorus compound used as an insecticide and then as an anthelmintic, especially for S. haematobium. Metrifonate is a prodrug that is converted nonen-zymatically to dichlorvos (2,2-dichlorovinyl dimethyl phosphate, DDVP), a potent cholinesterase... 

Recently, the dehalogenation method was further modified by using 1,2-dichlorovinyl ethers 62 as starting compounds" ". Loffler and Himbert applied the reaction of 1,2-dichlorovinyl ethers 62 with butyllithium to generate lithium alkoxyacetylides 61, which were subsequently quenched with ketones or arylated by the palladium-catalyzed crosscoupling with aryl halides to yield alkoxyarylacetylenes 63 (equation 37)". ... 

Trichloroethylene is a versatile chemical compound used extensively in vapour degreasing of metals, and to a more limited degree, as a solvent for dry-cleaning and for adhesives. Although the major rate of elimination of trichloroethylene, regardless of the method of exposure, in the rat is by exhalation through the pulmonary system (Daniel 1963), in man the nephrotoxic and genotoxic N-acetyl-S-dichlorovinyl-L-cysteine as an urinary metabolite was found after occupational exposure to 1,1,2-trichloroethylene (Birner et al. 1993). 

Synthesis. The first set of compounds discussed are 2-aryl-5 dichlorovinyl- (1, X-Cl) and 2-aryl-5-dibromovinylthiophenes (1, X-Br). Comparing this set of compounds with a-T, the central thiophene is unchanged and the terminal thiophenes are replaced by substituted phenyl groups and the dihalovinyl moiety. 

As the intention was to synthesize new inhibitors of acetylcholinesterase, the anticholinesterase activity of the above-described phosphonates and phosphonothioates was studied. In 1978, Zakharova et al. examined the activity of dichlorovinyl-substituted carbaboranyl phosphonates 27-30 toward acetylcholinesterase and butyrylcholinesterase. As these compounds are analogs of 2,2-dichlorovinyl dimethyl phosphate (dichlorvos or DDVP) (26), their activity was compared with the activity of this known insecticide. As shown in Table 2.1, compounds 27-30 exhibit remarkably lower activity toward both enzymes than the phosphate DDVP. The replacement of an alkoxyl group with the bulky carborane moiety increases the steric demand of the compound and therefore hinders binding on the surface of the enzyme and the following phosphorylation of the hydroxyl group of serine. Additionally, the type of inhibition changed in snch a way that the compounds exhibit reversible instead of irreversible binding. The substituents at the second carbon atom of the carborane core have only minor influence on the inhibitor activity. 

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