The palladium-catalyzed asymmetric side-chain C(α)-allylation of 2-alkylpyridines, without using an external base, was developed. The high linear selectivities and enantioselectivities were achieved using new chiral diamidophosphite monodentate ligands. Given that the reaction conditions do not require an external base, this catalyst system enabled chemoselective C(α)-allylation of 2-alkylpyridines containing α-carbonyl C-H bonds, which are more acidic than α-pyridyl C-H bonds.

No abstract

The palladium-catalyzed asymmetric side-chain C(a)-allylation of 2-alkylpyridines,w ithout using an external base,was developed. The high linear selectivities and enantioselectivities were achieved using new chiral diamidophosphite monodentate ligands.Given that the reaction conditions do not require an external base,t his catalyst system enabled chemoselective C(a)-allylation of 2-alkylpyridines containing acarbonyl CÀHb onds,w hicha re more acidic than a-pyridyl CÀHb onds. Scheme 1. Asymmetric side-chain C(a)-allylation of 2-alkylpyridines. LHMDS = lithium hexamethyldisilazide. Scheme 2. Palladium-catalyzed C(a)-allylation of 1a with 2a. dba = dibenzylideneacetone.

Recently active sites of Au nanoparticle / TiO 2 catalyst are discussed [1, 2]. Gold nanoparticles deposited on TiO 2 exhibit high catalytic activity of CO oxidation, in contrast to very low catalytic activity of bulk gold [1]. The candidates of active sites are Au surface and perimeter of interface of Au / TiO 2. Clarification of structure including oxygen is particularly promising for study of active sites with aberration-corrected TEM. We observed light atom (N) close to heavy atom (Ga) in GaN single crystal and demonstrated the validity of bright field STEM as shown in Fig.1 [3]. Another topic is in-situ transmission electron microscope (in-situ TEM). The shape change of catalyst nanoparticles in gas environments are observed [4]. We compared structures of Au nanoparticles on oxidizing and reducing TiO 2 surface and discussed the active sites of catalyst nanoparticles as shown in Fig. 2.

The remarkable catalytic activity of highly dispersed gold nanoparticles on TiO 2 for lowtemperature CO oxidation1 has been of tremendous interest. The catalytic activity has been attributed to structural features, such as particle size 1-5 , shape 1-2, 4-6 , and support [1][2][3][4][5][6] , particularly at the periphery and/or surface of the gold particles. The adsorption and activation of O 2 at Au/oxide catalysts via electronic origin of the contact [3][4]6 has been proposed as a critical step in the CO oxidation pathway. Recent insitu experiments with O 2 exposure to gold-deposited TiO 2 (110) surfaces demonstrated the nucleation of TiO 2 islands on the TiO 2 (110) surface 5,7 . Thus, O 2 is adsorbed at the TiO 2 surface, which can give rise to zero-order kinetics for CO oxidation 1 . It remains unclear how the edges and/or periphery of the gold particles behave under O 2 exposure. The periphery has been proposed as the activation site for the CO oxidation pathway, since the catalytic activity, which shows a d -2 dependence 1 , increases markedly for small particles with diameters below 2-3 nm 1,5,8 . Here, we observed Au/TiO 2 interfaces using insitu gas-injection transmission electron microscopy (TEM), and found Ti1 -x O 2 (x>0) regions in TiO 2 pillars (See Figs 1-2