EFFICIENT AND SELECTIVE TRANSITION-METAL FREE C–C BOND FORMING METHODS WITH BORON-STABILIZED NUCLEOPHILES

I. Synthesis of benzylic quaternary and tertiary carbons via site-selective nucleophilic aromatic substitution of aryl nitrile compounds. This chapter discusses the efficient and site-selective synthesis of benzylic all carbon quaternary and tertiary centers on heteroaromatic rings. This method utilizes reactive γ,γ-disubstituted and γ-substituted allyl diborons as pronucleophiles. The boronic esters are activated under mild Lewis base conditions and react smoothly with heteroaromatic nitriles. Quaternary carbon containing products are further derivatized to synthetically useful products. Finally, mechanistic studies are performed and provide evidence for a polar addition-elimination mechanism. II. Lewis base promoted synthesis of alpha-quaternary benzylic difluoromethylaromatics. This chapter discusses the discovery of a novel C–F functionalization reaction using γ,γ-disubstituted allyl diborons. Benzylic difluoromethylene products are afforded under mild Lewis base activation conditions and typically with high site selectivity. An initial substrate scope is explored with a diversity of substituents on the nucleophile fragment. Initial mechanistic studies suggest a radical mechanism is operative in this transformation. III. Studies towards the synthesis of monofluoroalkenes by selective C–F functionalization of trifluoromethyl arenes. This chapter discusses the discovery of a novel synthesis of aryl substituted monofluoroalkenes. This method uses geminal alkyl and benzylic diborons as nucleophiles to selectively functionalize C–F bonds of trifluoromethylarenes. Initial reactivity suggests an Z selective synthesis of monofluoroalkenes. Several modes of reactivity are explored to optimize the formation of monofluoroalkene products.