The asymmetric conjugate addition of arylcopper reagents derived from aryl Grignard reagents and copper(I) iodide to a chiral 1-[2-(p-tolylsulfinyl)]pyrrolyl cinnamide proceeded smoothly to give (3R)-adducts with high diastereoselectivities (> or =92% de) in high yields. Conjugate additions either of the cinnamide with the alkyl Grignard reagent-copper(l) iodide combination or of the crotonamide derivative with aryl Grignard reagent-copper(l) iodide gave moderate to good diastereoselectivities. With these sulfinyl pyrrolyl alpha,beta-unsaturated amides, the chiral auxiliary was efficiently recovered without any loss of optical purity after asymmetric conjugate addition. 相似文献
We report novel nanoporous polyimides formed from jungle‐gym‐type rigid polyimide gels by supercritical CO2 drying. By virtue of supercritical CO2 drying to avoid the collapse of nanostructure, porosity above 90 vol.‐% was achieved. We found a rich variety of nanoporous structures in the range of 50–800 nm such as crisp fragments, minute network, and highly‐connected beads. These characteristic structures were formed by the competitive progress of liquid‐liquid phase separation and crystallization induced due to the two chemical reactions of end‐crosslinking and thermal imidization during gelation.
In the title compound, [Pd(C6H7N2O3)2(C2H8N2)]·5.5H2O, the Pd atom is coordinated by two 1,3‐dimethylbarbiturate anions through a deprotonated tetrahedral carbon and the enolate oxygen. The Pd—N bond length of 2.078 (2) Åtrans to the C atom is shorter than the Pt—N distance of 2.098 (3) Å in the Pt analog. 相似文献
We have used in situ scanning tunneling microscopy (STM) to study the facet formation in the selective growth of pyramidal Si nanocrystals on Si(0 0 1) windows in ultrathin 0.3-nm-thick SiO2 films. Broad (0 0 1) surfaces developed as the top of the crystals, and {1, 1, (2n+1)} (n=1–6) facets formed the sidewalls. As growth continued, the slope angle of sidewall facets increased, and {1, 1, 9} and {1, 1, (2m+1)} (0 <m < 4) facets often came to coexist on the sidewalls. On well-oriented Si(0 0 1) surfaces, layer-by-layer growth in the [0 0 1] direction was dominant. On vicinal Si(0 0 1) surfaces, lateral step growth took place in the initial stage, and the layer-by-layer growth was suppressed until after a large (0 0 1) surface had formed as the top of the crystal. 相似文献
Optical Review - We propose a layout estimation method for multi-layered ink using a measurement of the line spread function (LSF) and machine learning. The three-dimensional printing market for... 相似文献
The enantioselective synthesis of distorted π-extended chiral triptycenes, consisting of three distinct aromatic rings, has been achieved with high ee value of 87 % by the cationic rhodium(I)/segphos complex-catalyzed enantioselective [2+2+2] cycloaddition of 2,2′-di(prop-1-yn-1-yl)-5,5′-bis(trifluoromethyl)-1,1′-biphenyl with 6-methoxy-1,2-dihydronaphthalene followed by the diastereoselective Diels–Alder reaction and aromatization. Demethoxy derivatives were also synthesized by the C−O bond cleavage. In this synthesis, the use of the electron-deficient diyne and the electron-rich alkene is crucial to suppress the undesired strain-relieving carbocation rearrangement and stabilize the distorted triptycene structure. 相似文献