Radical relay chlorination catalytic turnover

Template-catalyzed remote chlorination reactions have also been examined in molecular complexes. In one early study (Scheme 24), ion pairing was used to hold a charged template near a chaig substrate. Selective catalyzed radical relay chlorination was observed, but the selectivity was not as good as has been seen when the template is covalently attached to the substrate. In more recent work better selectivity and some catalytic turnover has been observed. 

Catalytic turnover has also been seen in radical relay chlorinations in which the template is temporarily linked to the substrate in a mixed metal complex. The steroid phosphate (22) and catalytic ligand... 

Catalytic turnover has also been seen in radical relay chlorinations in which the template is temporarily linked to the substrate in a mixed metal complex. The steroid phosphate (22) and catalytic ligand (23) both bind to zinc in a mixed complex, and the iodine atom of (23) directs chlorination of (22) at C-9 with reasonable selectivity (Scheme 25). Five or more turnovers are seen, when only 10% of the catalyst (23) is used. ... 

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