This first chapter describes a new synthetic method for the synthesis of allenoates from alkynals catalyzed by N-heterocyclic carbene. This persistent carbene is relatively more stable than the classical carbene and people employed NHC as an organocatalyst. The action of NHC mainly targets on the aldehyde functionality which can transform the electrophilic aldehyde into a nucleophilic Breslow intermediate via an umpolung process....[ Read more ]

This first chapter describes a new synthetic method for the synthesis of allenoates from alkynals catalyzed by N-heterocyclic carbene. This persistent carbene is relatively more stable than the classical carbene and people employed NHC as an organocatalyst. The action of NHC mainly targets on the aldehyde functionality which can transform the electrophilic aldehyde into a nucleophilic Breslow intermediate via an umpolung process.

The design in this project employed the alkynal substrate with a leaving group incorporated at the γ-carbon. Once the umpolung process is initiated, the Breslow intermediate is hypothesized to trigger the elimination of the leaving group via the conjugated system. The active cumulative allenol generated can further react to give the final product.

Methanol was found to be very crucial in the project as it was employed as the solvent and the nucleophile. Other common solvents were not capable of optimizing the synthesis of allenoate, including ethanol and isopropanol. Due to the uniqueness of methanol, the product was restricted as methyl allenoate.

The next chapter describes a highly efficient Suzuki cross-coupling reaction using recyclable palladium/vitamin-B₁ nanospheres at room temperature. The large palladium nanosphere has a diameter of 500 nm which is much larger than normal nanoparticles; however, many nanocrystals can be found on the surface of the large nanosphere. These Pd(0) nanocrystals help to increase the surface area and promote the catalytic activity. The large palladium/vitamin-B₁ nanospheres can be reused for three times without significant decrease of catalytic efficiency. The easy operation and mild condition required make this catalyst to have wide applications in organic synthesis.