Selective mixed halogenation

Selective mixed halogenation of zirconacyclopentadienes is attractive from a synthetic point of view. Indeed, the successive treatment of zirconacyclopentadienes with N-chloro-succinimide (NCS) followed by iodine, N-bromosuccinimide (NBS)/I2, or NCS/NBS selectively affords chloroiododienes, bromoiododienes, and chlorobromodienes, respectively (Eq. 2.17) [25],... 

Fiedler, H., Schramm, K.-W. (1990) QSAR generated octanol-water partition coefficients of selected mixed halogenated dibenzo-dioxins and dibenzofurans. Chemosphere 20, 1597-1602. 

Hara et al. (1980) employed GC/MS for the analysis of trace amounts of mixed halogenated compounds in the blood and tissue of humans. Identification and quantitative analysis of various compounds was achieved by monitoring the mass fragments for selectively molecular, abundant or characteristic ions for each compound. Thus the monitoring ion (m/z) for quantification of 1,1 -dichloroethane was set at 83 [(M) -CH3]. A lower detection limit of 10 to 20 pg per sample was achieved. 

Thiophenes substituted at C-2 were selectively halogenated at C-5 under biphasic conditions, though in the case of 2-methylthiophene, 10% of isomeric 2-methyl-3-chlorothiophene was also identified [96]. In this way, thiophenes with mixed halogens can be obtained. Chlorination and bromination of 2-iodothiophene gave 2-chloro-5-iodothiophene and 2-bromo-5-iodothiophene, respectively (Scheme 63). 

Halogenation of hydrogermanes using organic or inorganic halides is the primary method for the synthesis of these species, although selectivity is usually lacking.1,116,117 A versatile method for the preparation of various mixed... 

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