Sequential Double Olefination of 2-(Arylmethylidene)-2-phosphonoacetonitrile with Dimsyl Lithium and Aldehydes: A Domino Route to Densely Substituted 1,3-Butadienes

ZnCl2-mediated stereo- and chemoselective synthesis of vinylphosphonates

A highly chemo- and stereoselective synthesis of diethyl (E)-2-(alkylidene)-2-phosphonoacetonitriles via the Knoevenagel condensation reaction of carbonyl compounds with diethyl cyanomethylphosphonate in the presence of zinc chloride has been achieved. By the presented method, various E-isomers of arylmethylidene phosphonates rather than Horner-Wadsworth-Emmons olefination products were obtained in good to excellent yields. Their E configurations were determined by X-ray diffraction and NMR analyses. In addition, DFT calculations provided insights into the chemo- and stereoselectivity of the reaction.

Energy and Electron Transfer Cascade in Self-Assembled Bilayer Dye-Sensitized Solar Cells

Current high efficiency dye-sensitized solar cells (DSSCs) rely on the incorporation of multiple chromophores, via either codeposition or preformed assemblies, as a means of increasing broad band light absorption. These strategies have some inherent limitations including decreased total light absorption by each of the dyes, low surface loadings, and complex synthetic procedures. In this report, we introduce an alternative strategy, self-assembled bilayers, as a simple, stepwise method of incorporating two complementary chromophores into a DSSC. The bilayer devices exhibit a 10% increase in J_sc, V_oc, and η over the monolayer devices due to increased incident photon-to-electron conversion efficiency across the entire visible spectrum and slowed recombination losses at the interface. Directional energy and electron transfer toward the metal oxide surface are key steps in the bilayer photon-to-current generation process. These results are important as they open the door to a new architecture for harnessing broadband light in dye-sensitized devices.

Wittig olefination between phosphine, aldehyde, and allylic carbonate: a general method for stereoselective synthesis of trisubstituted 1,3-dienes with highly variable substituents

A clean and salt-free Wittig olefination between phosphines, aldehydes, and allylic carbonates is described. It represents a general method for convenient and efficient synthesis of 1,2,4-trisubstituted 1,3-dienes from readily available starting materials. This method exhibits high synthetic efficiency, high stereoselectivity, and high variability of substituent.