Polyhomologation of organoboranes with sulfur ylides. A new polymethylene synthesis

The polyhomologation of trialkylboranes has been developed as a new synthetic strategy for polymethylene. The reaction involves the successive homologation of methylene groups at all three substituents on boron. Sulfur ylides serve as the methylene source. Polyhomologation provides an unprecedented level of control over the degree of polymerization based on the initial molar ratio of sulfur ylide to trialkylborane. Very narrow molecular weight distributions (PDI's) resulted in the polymethylene preparations. These critical polymerization control factors were observed over a wide range of molecular weights using many different trialkylborane initiators. A variety of functionalized organoboranes have been used in the polyhomolgation reaction resulting in new telechelic polymethylene. The initial product of polyhomologation, tris-polymethylene borane, is amenable to organoborane transformations which result in novel polymethylene architectures not available from ethylene polymerizations.