Nitrile, conversion amidoxime

The relative initial ratio of acrylonitrile to butadiene and degree of conversion of nitrile to amidoxime are directly related to the resultant film s solubility parameter and glass transition temperature. Ideally, the concentration of amidoxime functional groups would be maximized while the coating s solubility parameter is matched to the vapor to be detected and the glass transition temperature is kept below room temperature. In practice, the conversion limitations are set by the reaction conditions of limited polymer solubility, reaction temperature and time. Three terpolymers of varying butadiene, acrylonitrile and amidoxime compositions were prepared as indicated in Table 1. 

The conversion of the polystyrene-supported selenyl bromide 289 into the corresponding acid 290 allowed dicyclohexylcarbodiimide (DCC)-mediated coupling with an amidoxime to give the 1,2,4-oxadiazolyl-substituted selenium resin 291 (Scheme 48). Reaction with lithium diisopropylamide (LDA) and allylation gave the a-sub-stituted selenium resin 292, which was then used as an alkene substrate for 1,3-dipolar cycloaddition with nitrile oxides. Cleavage of heterocycles 293 from the resin was executed in an elegant manner via selenoxide syn-elimination from the resin <2005JC0726>. 

The butadiene (80%)-acrylonitrile(17%)-aerylamidoxime(3%) terpolymer was prepared by reacting 2.5g butadiene 80%)-acrylo-nitrile(20%) copolymer (Aldrich) in 150 ml xylene with 1.61g hydro-xylamine hydrochloride in 12 ml n-butanol (freed of HC1 immediately before addition by method of Hurd (4) by dropwise addition under nitrogen. Reaction time and temperature were 23 hr. and 90-95°C. The polymer product was worked up by slowly adding the reaction mixture to 500 ml ether with rapid stirring. The precipitated polymer was allowed to settle, the supernate decanted and the polymer resuspended and washed with two 100 ml portions of ether followed by vacuum drying. Yield 2.04g (81%). Conversion of nitrile functional groups to amidoxime groups was 15% by infrared absorption. 

High yields of the nitriles (67) were also observed when Ar = Me. Another unusual intramolecular rearrangement is the conversion of the amidoxime (68) to the cyanohydrin (70) by hot water followed by nitrous acid at 0°. The hydroxyamidoxime (69) was shown to be an intermediate [164]. 

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