2.2- dichlorovinyl chloroformate

Fluoroformates (Ref. 88) and phenyl iodoformate (Ref. 89) used here were prepared according to literature procedure (see also farther on in this section). The preparation of isopropenyl chloroformate, as well as 2,2-dichlorovinyl chloroformate will be presented in section 3-2-Z-4. 

The facile preparation of 1,2,2,2-tetrachloroethyl chloroformate by treatment of chloral with phosgene in the presence of a reusable naked Cl- catalyst has been already described in section 3-2-2-3. We thought that if this chloroformate could be induced to undergo a Boord elimination of chlorine, the desired 2,2-dichlorovinyl chloroformate would be easily available as shown in scheme 114. 

It is known that the optical absorption which is the major drawback of the classical plastic materials such as PMMA, is dominated by the higher harmonics of the carbon-hydrogen stretching vibrations. The value of polymers from 2,2-dichlorovinyl chloroformates derivatives has to do with their lower optical absorption as compared to standard plastics in the visible and near-infrared regions of the spectrum (0.6 to 1.5 J.m). Some new 1,2-dichlorovinyl carbonates prepared by standard procedures in 90-95 % yield for that purpose are gathered in table 3-19 (Ref. 169). 

A report published thirty years ago (Ref. 164) outlined the potential insecticidal activity of 2,2-dichlorovinyl carbamates and carbonates. However, progress in this area has been stifled because 2,2-dihalovinyl chloroformates were unknown. For the preparation of the phosphonato ester (A) assumed to exhibit interesting insecticidal properties as compared to the well known insecticide Dichlorvos, we needed the heretofore unknown 2,2-dichlorovinyl chloroformate [see scheme 113]. 

Dichlorovinyl chloroformate 104, a stable and active acylating agent (e.g. for the protection of alcohols in acidic media) was prepared for the first time from 1,2,2,2-tetrachloroethyl chloroformate 103 (an a-chloroalkyl chloroformate synthesized by treatment of chloral 102 with phosgene in the presence of a reusable naked Cl catalyst) by dehalogenation with Zn dust [58]. 

Dichlorovinyl chloroformate (for a preparation, see Section 4.2.1 Chloro-formylation ), the key intermediate for the preparation of the phosphonato ester 294, which is assumed to exhibit interesting insecticidal properties by analogy with the well-known insecticide Dichlorvos, was synthesized from chloral and phosgene in the presence of reusable naked chloride ions and subsequent dechlorination with Zn [215]. 

Despite these strong omens of failure, the reaction was successfully performed (Ref. 165, 166). When zinc dust was added in small portions to a solution of 1,2,2,2-tetrachloroethyl chloroformate in THF at room temperature, dichlorovinyl chloroformate was isolated in 75% distilled yield. Initiation of the reaction after addition of the first portion of zinc is variable in time and no more zinc should be added until the first portion has been consumed to... 

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. 

By action of excess secondary amine on chloroform in the presence of sodium alkoxide some form-amidinium salts (182 equation 102) have been prepared. The aminolysis of. -dichlorovinyl ketones or trihalocyclopropenes gives rise to the amidinium salts (183) and (184) (Scheme 24), respectively. ... 

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. 

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