Synthesis of Novel Organoboron Polymers by Heloboration Polymerization.

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Organoboron polymers are expected as a novel type of reactive polymers. In this study, we explored a novel methodology for the preparation of organoboron polymers by the reaction of terminal diyne with boron tribromide. We termed this haloboration polymerization.As a typical example, the polyaddition between 1, 7-octadiyne and boron tribromide produced the corresponding poly (organoboron halide) as a brown solid. This polymer was soluble in common organic solvents such as chloroform and dichloromethane. The molecular weight of the obtained polymer was measured by GPC, from which Mn and Mw were found to be 5, 200"and 15, 500, respectively. The structure of the polymer was supported by its ^1H-, ^<11>B-NMR, IR and UV spectra. The present haloboration polymerization. was proved to proceed by cis addition of B-Br to C*C. In this haloboration polymerization, various diynes can be used to produce the corresponding poly (organobron halide)s.During the precipitation of the polymer into ethanol, the replacing reaction of B-Br to B-OET was observed. The reaction of the polymer with diol or with H_2O caused gelation. The B-Br bond in the polymer was subjected to the further haloboration reaction with phenylacetylene. The characteristic property of the polymer as a poly (Lewis acid) was also demonstrated by the reaction with THF to produce 4-bromo-, l-butanol after hydrolysis.