ãInverse electron demand asymmetric cycloadditions of cyclic carbonyl ylides catalyzed by chiral Lewis acids-Scope and limitations of diazo and olefinic substratesã?was written by Suga, Hiroyuki; Higuchi, Satoshi; Ohtsuka, Motoo; Ishimoto, Daisuke; Arikawa, Tadashi; Hashimoto, Yuta; Misawa, Shunta; Tsuchida, Teruko; Kakehi, Akikazu; Baba, Toshihide. Category: pyridine-derivatives And the article was included in Tetrahedron on April 17 ,2010. The article conveys some information:
High enantioselectivities (94-96% ee) were obtained for the inverse electron-demand 1,3-dipolar cycloadditions between cyclohexyl vinyl ether and 2-benzopyrylium-4-olate generated via Rh2(OAc)4-catalyzed decomposition of o-methoxycarbonyl-α-diazoacetophenone. The reactions were effectively catalyzed by Eu(OTf)3, Ho(OTf)3, or Gd(OTf)3 complexes (10 mol %) of chiral 2,6-bis[(4S,5S)-4,5-diphenyl-2-oxazolinyl]pyridine. The reactions with the other electron-rich dipolarophiles such as allyl alc., 2,3-dihydrofuran, and butyl-tert-butyldimethylsilylketene acetal showed moderate enanantioselectivities (60-73% ee). Good to high enantioselectivities (73-97% ee) were also obtained for the cycloadditions between 3-acyl-2-benzopyrylium-4-olates, generated from Me 2-(2-diazo-1,3-dioxoalkyl)benzoates and Bu or cyclohexyl vinyl ethers, in the presence of binaphthyldiimine (BINIM)-Ni(II) complexes (10 mol %). Under similar conditions, the reaction between Me 2-(2-diazo-1,3-dioxohexyl)benzoate and 2,3-dihydrofuran was highly endo-selective, and moderately enantioselective (70% ee). For the BINIM-Ni(II)-catalyzed reactions of cyclohexyl vinyl ether, the use of an epoxyindanone as the 3-acyl-2-benzopyrylium-4-olate precursor revealed that the chiral Lewis acid can function as a catalyst for asym. induction. The scope of the cyclic carbonyl ylides was extended to those generated from 1-diazo-2,5-pentanedione derivatives, which were reacted with Bu or TBS vinyl ether and catalyzed using the (4S,5S)-Pybox-4,5-Ph2-Lu(OTf)3 complex to give good levels of asym. inductions (75-84% ee). Absolute structure of I was determined by XRD. In addition to this study using 2,6-Bis((4S,5S)-4,5-diphenyl-4,5-dihydrooxazol-2-yl)pyridine, there are many other studies that have used 2,6-Bis((4S,5S)-4,5-diphenyl-4,5-dihydrooxazol-2-yl)pyridine(cas: 410092-98-7Category: pyridine-derivatives) was used in this study.
2,6-Bis((4S,5S)-4,5-diphenyl-4,5-dihydrooxazol-2-yl)pyridine(cas: 410092-98-7) belongs to pyridine derivatives. The ring atoms in the pyridine molecule are sp2-hybridized. The nitrogen is involved in the π-bonding aromatic system using its unhybridized p orbital. Category: pyridine-derivativesThe lone pair is in an sp2 orbital, projecting outward from the ring in the same plane as the σ bonds.