Gas-Phase and Condensed-Phase Studies of Small Reactive Intermediates

Nitriles are an integral functional group in many chemical industries. A new methodology for the dehydration of amides to nitriles has been developed using a palladium catalyst. The reaction conditions are robust and able to tolerate a wide variety of functional groups and substrates. The substrate scope can be broken into 4 main types of substrates including: alkyl, aromatic, cinnamic, and α, β, δ, γ-unsaturated amides. Mechanistically, the amide goes through a water exchanging mechanism to generate acetamide in equal parts to the nitrile. Cyclopropanols are important precursors for the generation of beta-carbonyl radicals. In the presence of a single-electron oxidant, the beta-carbonyl radical can be generated and trapped. In this methodology, N-aryl acrylamides were used as a trapping reagent for the beta-carbonyl radical and, upon a second single-electron oxidation, can form 2-oxindoles with carbonyls available for further derivitization. 2-oxindoles are important structural motifs in natural products with medicinal properties and this methodology explores the scope for the formation of these small molecules. Aryl Nitrenes are the other reactive intermediates of interest. Although extensively studied over the past 30 years, phenylnitrenes have a propensity for undergoing rearrangement reactions and forming polymeric tars. This is in direct contrast with phenylcarbenes which do not undergo rearrangement and can participate in bimolecular chemistry. The electronics of phenylnitrene can be manipulated to avoid the rearrangement reactions and change the reaction pathway to bimolecular chemistry. Studies of substituted phenylnitrenes took place in both the gas-phase and condensed-phase in order to understand the total effect of the substituent on the electronic state of the nitrene. In these studies, the phenylnitrene was substituted at the ortho position with either a hydroxyl group or a benzyl group which the former could act as a weak π-donor and the latter as a strong π-donor