Modified Wurtz coupling

Higher members like [23](l,4)cyclophane (34) are available in a modified Wurtz coupling reaction [38]. Cram [32] described the complexation of only one benzene ring of 34, while Elschenbroich [39] succeeded in the complexation of the second and third benzene ring by variation of stoichiometry and prolonged reaction time (Fig. 6b). 

The starting bibenzyl was prepared from -methoxybenzyl chloride by a modified Wurtz reaction. The checkers found the procedure described by Buu-HoY and Lavit inadequate and used the copper(I) chloride-catalyzed coupling of -methoxy-phenyl magnesium chloride in its place. 

All of the polysilanes used in this study were prepared by the modified Wurtz-type coupling of substituted dichlorosilanes by sodium dispersion in an inert aromatic solvent as previously described (23.24). Poly(di-n-hexylgermane) was similarly prepared from di-n-hexyldichlorogcrmane (16). All of the polymer samples... 

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