Chloromethylated polystyrene Subject

The cationic polymer 40, prepared from chloromethylated polystyrene and 1, was subjected to ion-exchange to give the hydroxide or fluoride derivatives, and used in the asymmetric addition of 6 to 7 giving (S)-8 in 27% ee (Fig. 6) [36]. 

Trying to completely avoid the technically unpleasant process of chloromethylation, Negre et al. [48, 49] prepared a linear styrene copolymer with p-vinylbenzyl chloride and then subjected the product to self-crosslinking. Alternatively to the earlier-mentioned crosslinking of linear polystyrene with MCDE, this procedure results in local inhomogeneity of crosslinks distribution, because of the uneven distribution of the two comonomers along the initial chain (the monomer reactivity ratios of vinylbenzyl chloride and styrene are 1.41 and 0.71, respectively). Nevertheless, vinylbenzyl chloride became a popular comonomer for styrene and DVB in the preparation of beaded hypercrosslinked products [50-52]. 

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