Photoredox-Catalyzed Cascade Reactions Involving Aryl Radical: Total Synthesis of (±)-Norascyronone A and (±)-Eudesmol.

Herein, we have developed two types of photoredox-catalyzed cascade reactions using diaryliodonium salts for the concise synthesis of norascyronone A and ß-eudesmol. A rationally designed photoredox-catalyzed arylation/cyclization/Friedel-Crafts cascade reaction of enone was exploited to generate the norascyronone polycyclic skeleton. A visible-light-induced radical cyclization/acyloxy-migration reaction was explored to forge the decalin skeleton of eudesmol, and mechanistic studies indicated the reaction was initiated by one-electron oxidation of the enol ester.

From Metal Thiobenzoates to Metal Sulfide Nanocrystals: An Experimental and Theoretical Investigation.

A simple preparation of metal sulfide nanoparticles via the decomposition of thiobenzoate precursors at room temperature is presented and discussed. Long chain alkylamines were found to mediate the breakdown of metal thiobenzoates, such as those containing Ag, Cu, In and Cd, to produce uniform Ag2S, Cu2-xS, In2S3 and CdS nanoparticles respectively. The long chain amines are assumed to play dual roles as the nucleophilic reagent and the capping agent. It was found that sizes of the nanoparticles can be controlled by changing the type of amine used, as well as the molar ratio between amine and the precursor. We performed DFT calculations on a proposed mechanism involving an initial nucleophilic addition of amine molecule onto the thiocarboxylates. The proposed reaction was also confirmed through the analysis of by-products via infrared spectroscopy. On the basis of this understanding, we propose to manipulate the stability of the precursors by coordination with suitable stabilizing groups, such that the reaction kinetics can be modified to generate different nanostructures of interest.

Nanoparticle fractionation using an aligned carbon nanotube array.

A technique utilizing the capillary assisted sieving capability of carbon nanotubes (CNTs) to achieve fractionation of nanoparticles of small size distribution is presented. By dipping aligned CNT arrays into a solution comprising different sized quantum dots (QDs), size-selective gradient decoration of QDs onto CNTs is achieved. The fractionating capability of CNTs is also demonstrated for poly-dispersed manganese doped zinc sulfide nanoparticles and QDs of varying sizes and chemical compositions, which we attribute to the size-selective sieving effect of CNTs. By controlling the terminating point for the flow of QDs across the CNT array, a QD size specific CNT/QD hybrid structure is achieved.

Shape-controlled synthesis of zinc oxide: a simple method for the preparation of metal oxide nanocrystals in non-aqueous medium.

A general and facile approach has been developed to prepare various metal oxide nanocrystals from commercially available metal acetate precursors using an amine-mediated reaction. The influence of temperature and capping agents on the yield and final morphology of the metal oxides nanocrystals was investigated. The approach was applied in the synthesis of shape-controlled ZnO nanocrystals. ZnO nanowires, nanorods, bullets and triangular nanocrystals were successfully prepared by tuning the molar ratio between amine to zinc acetate precursor. On the basis of FTIR and NMR spectroscopic studies, we propose that the amine could mediate the breakdown of the metal acetates through a nucleophilic attack mechanism. The results suggest that amine can play dual role as both the attacking agent and capping agent in this new methodology.