Dehalogenation multiple

Some examples in the area of nucleoside chemistry are the reductions of bromide 10, chloride 11, and selenide 12 in 94, 92, and 87% yields, respectively, at 80 °C using AIBN as the radical initiator.Multiple dehalogenations are possible in a one-pot procedure by using the corresponding equivalents of (TMSlsSiH. ... 

The above evidence should not be interpreted as meaning that hydrolytic dehalogenation can never be demonstrated unambiguously. Indeed, the next subsection will document reactions of multiple dehalogenation that are only consistent with a hydrolytic mechanism. But before doing so, we examine here the hydrolysis of medicinal nitrogen mustards and of their sulfur analogue, the infamous sulfur mustard. 

The novel antitumor agent penclomedine (11.38) provides another example of multiple dehalogenation [74], In the perfused rat liver, rapid biotransformation occurred by two major pathways, namely oxidative O-demethyla-tion at C(4), and formation of penclomic acid by dechlorination of the CC13 moiety. The proposed sequence of reactions ... 

The term dehalogenation generally denotes any reaction in which one or more halogen atoms leave a molecule, e.g. in reductive dehalogenation. In this section, dehalogenation is used in the sense of 1,2-didehalogenation leading to the formation of a multiple bond. 

This reaction is the dominant dehalogenation pathway in reduction of halogenated methanes [84] and haloacetic acids [85]. In Fig. 4, this reaction is illustrated for perchloroethene (PCE), where complete dechlorination by this pathway requires multiple hydrogenolysis steps. The relative rates of these steps are a critical concern because they determine whether... 

Hydrolysis of esters and ethers, hydrolytic cleavage of C—N single bonds, hydrolytic cleavage of nonaromatic heterocycles, hydration and dehydration at multiple bonds, new atomic linkages resulting from dehydration reactions, hydrolytic dehalogenation removal of hydrogen halide molecules, various reactions. 

Reduction of NHC-borane adducts has proven useful for purposes other than the synthesis of boron-boron multiple bonds. Bissinger et al. [124] successfully employed this technique to prepare a trapped form of borylene, BH. NHC-stabi-lized dichloroborane (IMe-BHCl2) was prepared from BHCl2 SMe2 and then subsequentiy dehalogenated with 2 equivalents of sodium naphthalenide (NaN), yielding the naphthalene-trapped IMe BH adduct (Scheme 15.10). The authors propose that this reaction occurs via a [2+1] cycloaddition pathway and provide quantum chemical calculations to support this notion. 

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