Chromium, tricarbonyl Subject

Davies resolved o-anisaldehyde(tricarbonyl)chromium 158 subjecting the racemic valinol-derived imines 159 and 160 adsorbed onto neutral alumina to slow elution with ether [95]. A single enantiomer of 158 was first eluted, resulting from hydrolysis of imine 159, followed by the imine 160 of the second enantiomer (dichloromethane-methanol 5 1 as eluent). This latter imine may be prevented from hydrolysis through reversible formation of the oxazoHne 161. 

The optically pure tricarbonyl chromium(O) complexes 116 have proven to offer an effective shielding of one of the faces of the alkene. Complex 116 was subjected to a 1,3-dipolar cycloaddition with the sterically crowded nitrile oxide 117 (Scheme 12.39) (172). The reaction proceeds at room temperature to give a 70% yield of 118. After removal of the tricarbonylchromium moiety by a light induced oxidation with air, compound 119 was obtained with an optical purity of 98% enantiomeric excess (ee). 

Other polymers which have been the subject of thermal degradation studies include ethylene-vinyl acetate [29, 66, 67], ethylene-vinyl alcohol [68], poly(aryl-ether ketone) [69], poly-2-vinyl-naphthalene-co-methyl maleate [34], polyphenylenes based on diethyl-benzophenone [70], polyglycollide [71-73], poly(a-methylstyrene tricarbonyl chromium [74], polytetrahydrofuran [75], polylactide [76-78], poly(vinyl) cyclohexane [79], styrene-vinyl cyclohexane [80], isopropenylacetate-maleic dianhydride [80], polyethylene glycol containing a 1,3-disubstituted phenolic group [81], poly-2-vinyl naphthalene-co-methacrylate [34], collagen biopolymers [82], chitin graft poly (2-methyl-oxazoline - polyvinyl chloride blends [83], cellulose [32, 83-88] and side-chain cholestric elastomers [89, 90]. 

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