Alkenes, addition polyhalogenated compounds

Other polyhalogenated compounds can be used with similar success. CpFe(CO)2 dimer leads to the formation of mixtures of lactones and esters when reacted with an alkene and methyl trichloroacetate [79] with the lactone being the major product (Scheme 3.10). Similar results were reported earlier by Freidlina and Velichko [80]. FeCl3 and Fe(CO)5 are both suitable for catalyzing the addition of methyl dibromoace-tate to electron-deficient alkenes such as methyl propenoate. It was observed that the ratio of products (acyclic vs. lactone) could be tuned by varying the reaction conditions. In all cases, the acyclic product is predominantly formed. Only in the presence of a co-catalyst such as N,N-dimethylaniline are small amounts of lactone observed. Noteworthy, elevated temperatures (above 100 °C) are necessary for this transformation. 

The discovery of Minisci et al.,39 Asscher and Vofsi,40 and others41 of the transition metal catalyzed addition of haloalkanes to alkenes by a redox chain process (Scheme 14) has found vast synthetic applications.830,89 A recent summary has been given by van Koten et al.90 Virtually any olefin can serve as the source of reactive unsaturation, and a variety of polyhalogenated compounds such as alkyl halides,... 

Scheme 1. Kharasch addition of polyhalogenated compounds to alkenes.

Oxazetidines have been obtained by [2 + 2] addition of nitroso compounds to appropriate alkenes. Trifluoronitrosomethane reacts with polyhalogenated ethylenes (69JCS(C)2ll9), with styrene (65JGU855) or with allenes (73JCS(Pi)l56l) to give oxazetidines (e.g. Scheme 7). 

Many polyhalogenated alkenes are potent nephrotoxins. 2-Chloro-l, 1,2-trifluoroethylene (CTFE), trichloroethylene (TCE) and tetrafluoroethylene (TFE) are notable examples. The initial step in bioactivation of such compounds is the GSH-trans-ferase-catalyzed addition or addition-elimination of GSH. For example, in the liver, the action of GSH- transferase converts CTFE to S-(2-chloro- l,l,2-trifluoroethyl)glu-tathione (CTFG), TCE to S-(l,2-dichlorovinylglutathione (DCVG) and TFE to S-... 

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