Selective conversion of chloromethyl and bromomethyl groups to aminomethyl groups in multifunctional crosslinked polystyrenes

Abstract

A one-pot polymer-analogous preparation which effects the conversion of chloroalkyl or bromoalkyl groups in multifunctional polystyrene derivatives to aminoalkyl polystyrenes is described. The method involves the extension of the Delepine reaction in which chloromethyl or bromomethyl groups are converted in a single step to aminomethyl groups by treatment with hexamethylenetetramine. This method is selective in that other reactive functional groups, such as carbonyl and nitro, remain unaffected in contrast to the phthalimide synthesis which involves conversion to phthalimidomethyl resin followed by hydrazinolysis. Thus photochemically removable polystyrene resins like 3-nitro-4-aminomethyl polystyrene, aminoacetyl polystyrene and 2-aminopropionyl polystyrene can be prepared in a single step from the corresponding 3-nitro-4-chloromethyl polystyrene, bromoacetyl polystyrene or 2-bromopropionyl polystyrene. The residual halogen contents in these aminoalkyl resins were found to be in the range of 0.3-0.2 mmol/g starting with 4.2 mmol/g halogen, corresponding to 90-95% conversion. In the case of the linear soluble poly(vinylbenzyl chloride), quantitative conversion occurred with simultaneous crosslinking resulting in the formation of insoluble aminomethyl polymer.