Mercury phenyl bromodichloromethyl, reaction

In a similar manner, metapyridophanes 18 can be prepared by reaction of sodium trichloroacetate with pyrrole 17 (Scheme 8.3.5). The transformation can also be achieved with phenyl(bromodichloromethyl)mercury, albeit in lower yield. 

Carbenes were among the first reactants to be explored in addition reactions. Phenyl (bromodichloromethyl)-mercury has been used to introduce dichlorocarbene, which produced large optical changes at Fermi level transitions [27]. It was recently reported that under certain conditions dichlorocarbene is also able to effect a transition from... 

Examples of carbene insertions into the carbon-silicon bond of SCBs have been known since 1967, when Seyferth studied the behavior of SCBs exposed to dichlorocarbene, which was generated by thermolytic activation of phenyl(bromodichloromethyl)mercury <1967JA1538>. The reaction produces a mixture of products arising from Si-C and C-H bond insertions, with the major products being the ring-expanded silacyclopentanes that result from Si-C bond insertions (Scheme 30). 

Kinetic studies of the reaction of phenyl(bromodichloromethyl)mercury with olefins show that dichlorocarbene is liberated as a free species. Moreover, the fact that the reaction is insensitive to the effect of substituents in the phenyl group suggests that the extrusion process proceeds in a concerted process through a cyclic transition state, 5a or 5b.7c... 

An interesting new method of synthesis of carbonimidoyl dichlorides involves the addition of dichlorocarbene to aliphatic carbodiimides. Thus, reaction of phenyl(bromodichloromethyl)mercury (LXV) (the dichlorocarbene precursor) with diisopropylcarbodiimide produces isopropyl-carbonimidoyl dichloride (LXVI) in 63% yield... 

Qiloroform yields both the trichloromethyl anion and dichlorocarbene as reactive intermediates under basic phase transfer conditions. The trichloromethyl anion reacts with phenylmercuric chloride under these conditions to yield phenyl(trichloromethyl)-mercury (72%). The product is unstable, however, to the 50% aqueous sodium hydroxide solution usually used in phase transfer catalysis. When 10—15% aqueous sodium hydroxide solution was used, while maintaining the ionic strength by addition of potassium fluoride, the product survived. Reasonable yields of the mercury compound were thus obtained and the reaction was successfully extended to bromodichloromethane [yielding 64% of phenyl(bromodichloromethyl)mercury] and bromoform [yielding phenyl(tribromomethyl)mercury, 54%]. The transformation is illustrated in equation 3.18 [26]. 

Phenyl(dichlorofluoromethyl)mercury can also be obtained by reaction of phenyl(bromodichloromethyl)mercury with phenylmercuric fluoride, a novel halogen-exchange procedure which yields phenyl(trifluoromethyl)-mercury when applied to phenyl(tribromomethyl)mercury ... 

Phenylmercury(II) fluoride-hydrogen fluoride complex fluorinates phenyl(tribromo-methyl)mereury in 60-65% yield when the reaction is carried out in the presence of 48% hydrogen fluoride. Phenyl(trichloromethyl)mercury can be fluorinated to the trifluoromethyl derivative in this manner, but a reaction temperature of 90 C is required. Partial fluorination of (bromodichloromethyl)phcnylmcrcury to (dichlorofluoromethyl)phenylmercury in 60% yield can be achieved at room temperature, but attempted partial fluorination of phenyl(tri-bromomethyl)mercury, (dibromochloromethyl)phenylmercury, and (dibromofluoromethyl)-phenylmereury was unsuccessful phenyl(trifluoromethyl)mercury is the major product obtained.61... 

In the case of haloalkenes of low reactivity, tetrachloroethene and hexachlorocyclopropane are formed via subsequent reactions of dichlorocarbene generated from thermal decomposition of bromodichloromethyl(phenyl)mercury, for an example see ref 69. 

Using bromodichloromethyl(phenyl)mercury, vinyl acetate afforded 2-acetoxy-l,l-dichlo-rocyclopropane (1, 85%), dichlorocyclopropanation of other aldehyde enol esters would also be expected. The cyclopropane 1 ( 10%) together with 2-acetoxy-l,l,l-trichloropropane (2,10%) were formed when the dichlorocarbene was generated from sodium trichloroacetate, the chain product 2 results from the reaction of the trichloromethyl anion (for the mechanism, see ref 197). These reactions are described in Houben-Weyl, Vol. 4/3, pp 177-178. Under phase-transfer catalytic conditions (CHClj/base/PTC), with a typical catalyst such as benzyl-triethylammonium chloride, vinyl acetate gave 2 (65%) only (Houben-Weyl, Vol.E19b, ppl550-1551). 

Indeed, the reaction of an equimolar quantity of bromodichloromethyl(phenyl)mercury with alk-2-enoic acids affords the dichloromethyl esters. Dichlorocyclopropanation is only possible if a second mole of carbene source is used (see Houben-Weyl, Vol. 4/3, pp 178-179). Competition between acetic acid and cyclohexene for dichlorocarbene indicates that the acid is considerably more reactive.Furthermore, dichloromethyl 2,2-dichlorocyclopropane-carboxylates cannot be hydrolyzed to the corresponding acids. To avoid all of these difficulties, addition of dichlorocarbene, generated under nonhydrolytic conditions using dichloro-halomethyl(phenyl)mercury, to the bromides of alk-2-enoic acids is possible. 

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