PREPARATION AND REACTIVITY OF POLYEPOXIDES AND POLYKETONES - CATALYTIC-OXIDATION OF POLYBUTADIENES

The epoxidation of polybutadienes containing varying proportions of pendant (1,2-polymerized) and backbone (1,4-polymerized) double bonds with Bu(t)OOH catalysed by [MoO2Cl2(3-diethoxyphosphoryl)camphor] {systematic name: dichloro [(IR)-endo-(+)-3-(diethoxyphosphoryl)camphor] dioxomolybdenum(VI)} gives very high selectivity to epoxidation of the backbone double bonds. In the absence of molecular sieves some diol units are produced, but addition of molecular sieves (4A) prevents the formation of diols and greatly increases the rate of the reaction. With [Pt(Ph2PCH = CHPPh2)CF3(CH2C12)]BF, as catalyst and Bu(t)OOH as oxidant, polyketones are formed with pendant:trans:cis reactivities in the ratio 6:5:3. The introduction of ketonic functions on the pendant double bonds allows functionalisation on the carbon atom next to the main chain, a position that is otherwise difficult to functionalise. The polyepoxides are found to be unreactive towards ring-opening reactions with water, alcohols, amines etc., although ring-opening is observed in reactions with alcohols or carboxylic acids under forcing conditions in the presence of H2SO4 as a catalyst. Ring-opening is also observed with aryllithium reagents although Bu(n)Li gives allyl alcohol units in the backbone of the polymer. The polyketones are more susceptible to reaction, e.g. with 6-lithio-2,2'-bipyridyl and soluble polymer-bound bipyridyl is readily synthesised. The polymers are characterised by H-1 and C-13 NMR studies.