Gold(I)-Catalyzed Coupling Reactions for the Synthesis of Diverse Small Molecules Using the Build/Couple/Pair Strategy

The build/couple/pair strategy has yielded small molecules with stereochemical and skeletal diversity by using short reaction sequences. Subsequent screening has shown that these compounds can achieve biological tasks considered challenging if not impossible (‘undruggable’) for small molecules. We have developed gold(I)-catalyzed cascade reactions of easily prepared propargyl propiolates as a means to achieve effective intermolecular coupling reactions for this strategy. Sequential alkyne activation of propargyl propiolates by a cationic gold(I) catalyst yields an oxocarbenium ion that we previously showed is trapped by C-based nucleophiles at an extrannular site to yield α-pyrones. Here, we report O-based nucleophiles react by ring opening to afford a novel polyfunctional product. In addition, by coupling suitable building blocks, we subsequently performed intramolecular pairing reactions that yield diverse and complex skeletons. These pairing reactions include one based on a novel aza-Wittig-6π-electrocyclization sequence and others based on ring-closing metathesis reactions.Chemistry and Chemical Biolog

On the Possibility to Control an Atom Motion in a FCC Iron Nanocluster

The energy of the isolated iron nanocluster was calculated by molecular mechanics method using the Lennard-Jones potential depending on the position of impurity carbon atom and substitutional atoms of nickel. The cluster included a carbon atom, that drifted from an inside octahedral interstice to a direction ⟨022⟩ to the surface directly or to a tetrahedral interstice in ⟨1̅11⟩ direction and after that in ⟨222⟩ direction to the surface. In addition one of 14 iron atoms was replaced by a nickel atom (or pair atoms), the position of which was changing during simulation. It is shown that there were positions of a nickel atom that significantly affected nanoclusters energy. The calculation results indicated that position of a carbon atom in the octahedral interstice was more energetically favorable than tetrahedral interstice in the case of fcc nanocluster. On the other side, the potential barrier was smaller in the direction ⟨1̅11⟩ than in the direction ⟨022⟩. This indicates that there are two ways for carbon atom to drift to the surface of the nanocluster. The positions of nickel atoms were identified, which significantly affected the height of potential barriers of a tetrahedral and an octahedral interstice and determined the possible direction of carbon atoms drift. This allows manipulating atoms at the surface of nanocluster