BORANES IN FUNCTIONALIZATION OF OLEFINS TO AMINES

Heteroatoni groups such as boron or silicon can activate or direct synthetic reactions. Use of such activation has become of major importance in organic syntheses. Examples in this volume are BORANES IN FUNCTIONALIZATION OF DIENES TO CYCLIC KETONES BICYCLO[3.3.1]NONAN-9-ONE and BORANES IN FUNCTIONALIZATION OF OLEFINS TO AMINES 3-PINANAMINE. Use of trimethylsilyl or trimethyl-silyloxy groups to activate a 2-butenone or a butadiene are illustrated by the preparations 3-TRIMETHYLSILYL-3-BUTEN-... 

The addition of reagents containing X-H bonds in which X is more electronegative than H typically lead to addition across the M-C bond in the direction opposite to the addition of silane or borane to the early metal catalysts. Polymerization of etiiylene with lanthanide catalysts in the presence of phosphines generates phosphine-terminated polymers (Scheme 22.12) - by a mechanism in which the alkyl chain is protonated, and a metal-phosphido complex is generated. This phosphido complex then inserts olefin to start the growth of a phosphine-functionalized polyolefin. Marks subsequently showed that a similar process can be conducted witii amines. In this case, the bulky dicyclohexylamine was needed to sufficiently retard the rate of protonation to allow chain growth. The steric bulk also makes the olefin insertion more favorable thermodynamically. 

In the absence of hydrogen, metallocene-based catalyst systems produce well-defined polymers which are olefin- or aluminum-terminated. Miilhaupt has polymerized propylene with a chiral metallocene and MAO under conditions where P-hydrogen elimination was the predominant chain transfer process. In a post-polymerization functionalization, the olefin endgroups of the highly isotactic polypropylene chains were converted to bromo-, epoxy-, anhydride-, ester-, amine-, carboxylic acid-, silane-, borane-, hydroxy-, thiol-terminated polymers as intermediates for the preparation of block copolymers. Using olefin-terminated atactic and isotactic polypropylene formed with MAO-activated Cp2ZrCl2 and (EBTHI)ZrCl2 Shiono has synthesized amine- and aluminum-terminated polymers." ... 

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