Polymer LiAlH4-reduced

The authors acknowledge the very valuable contributions of K. B. Abbas, who provided samples of LiAlH4-reduced PVC and the original polymers used to prepare them, and they thank S. M. Vincent, D. J. Freed, and J. P. Luongo for analytical assistance. 

Aza-2,4-cyclopentadienone and 3-aza-2,4-cyclopentadienone are two reactive intermediates (75AG38) whose existence has been demonstrated by using the three-phase test. The precursor polymers for both compounds have been prepared (36) from maleimide, which was reduced with LiAlH4 and linked to the sulfonic polymer, and (39) by reaction between (37) and (38) (88JA4017 91JOC5417). 

This reduction technique has not necessarily been carried to its ultimate stage of development it is quite likely that the procedure could be improved. Nevertheless, this technique already seems far superior to the LiAlH4 method with respect to reaction velocity, safety aspects, and the reproducible production of a polymer that has been extensively reduced. Further evidence for the superiority of the new technique has been provided by 13C NMR studies, which will now be briefly described. 

In some very remarkable experiments, Bystrom et al. [77] were recently able to demonstrate high regio- and stereoselectivity in reactions inside the imprinted cavity. The steroid 12 was copolymerized as the template monomer, and removed by reduction. The hydroxyl group in the polymer newly formed from the carboxyl group was converted into an active hydride by LiAlH4. With the help of this polymer, androstan-3,I7-dione was reduced to the alcohol exclusively in position 17, whereas in solution or with a polymer with statistically distributed hydride groups it is reduced exclusively in position 3. 

The polymers were generated by suspension polymerization using DVB as comonomer and cross-linker. The ester groups were reduced with LiAlH4 to remove... 

The problem is apparently due to some residual aluminum that is hard to remove. If, however, the reduction is carried out in a iV-methylmorpholine solution, followed by addition of potassium tartrate, a pure product can be isolated. A -Methylmorpholine is a good solvent for reductions of various macromolecules with metal hydrides.In addition, the solvent permits the use of strong NaOH solutions to hydrolyze the addition complexes that form. Other polymers that can be reduced in it are those bearing nitrile, amide, imide, lactam, and oxime pendant groups. Reduction of polymethacrylonitrile, however, yields a product with only 70% of primary amine groups. Complete reductions of pendant carbonyl groups with LiAlH4 in solvents other than A -methyl-morpholine, however, were reported. Thus, a copolymer of methyl vinyl ketone with styrene was fully reduced in tetrahydrofuran. ... 

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