Reference

Chiral phosphine ligands modified by crown ethers: an application to palladium-catalyzed asymmetric allylation of b-diketones

Chiral phosphine ligands modified by crown ethers: an application to palladium-catalyzed asymmetric allylation of b-diketones. Sawamura, Masaya; Nagata, Hiroshi; Sakamoto, Hiroaki; Ito, Yoshihiko (Fac. Eng., Kyoto Univ., Kyoto 606-01, Japan). J. Am. Chem. 2304-94-1 and 874-23-7 are cas registry numbers. These chemicals are also mentioned in this article. Soc., 114(7), 2586-92 (English) 1992. CODEN: JACSAT. ISSN: 0002-7863. DOCUMENT TYPE: Journal CA Section: 29 (Organometallic and Organometalloidal Compounds) Section cross-reference(s): 23 Chiral ferrocenylphosphine ligands modified by monoaza or diaza crown ethers of varying ring sizes and linker chain lengths, e.g. I [n = 1, m = 2, X = O (II), NMe (III)], were synthesized. The reaction of the phosphine ligand modified by monoaza-18-crown-6 II and the bis(m-chloro)bis(p-allyl)dipalladium(II) complex in CDCl3 produced the (p-allyl)palladium(II) complex chelated by the two P atoms of II, leaving the crown ether moiety free. The 1H{1H} nuclear Overhauser effect study of the (p-allyl)palladium(II) complex suggests that the aza crown ether moiety of chiral ligand II is located at the proper position to interact with an incoming nucleophile. The palladium catalyst which was prepd. in situ by mixing the crown ether-modified chiral ligands and Pd2(dba)3×CHCl3 (dba = dibenzylideneacetone) was examd. for stereoselectivity and catalytic activity in the asym. allylation of unsym. substituted b-diketones under solid-liq., two-phase reaction conditions using KF as an insol. base in mesitylene. The ligands bearing monoaza-18-crown-6 or 1,10-diaza-18-crown-6 with an appropriate length of linker chain (II and III, resp.) significantly accelerated the allylation and showed fairly high enantioselectivity (up to 75% ee). It is proposed that a ternary complex involved a crown ether, a potassium cation, and an enolate anion attacks a (p-allyl)palladium(II) intermediate. .

1-(p-Chlorophenyl)-3,4-dimethyl-5,6,7,8-tetrahydropyrazolo[3,4-b]quinol ine

1-(p-Chlorophenyl)-3,4-dimethyl-5,6,7,8-tetrahydropyrazolo[3,4-b]quinol ine. Low, John Nicolson; Quiroga, Jairo; Portilla, Jaime; Cobo, Justo ( Department of Chemistry, University of Aberdeen, Old Aberdeen AB24 3UE, UK). Acta Crystallographica, Section E: Structure Reports Online, E59(11), o1657-o1658 (English) 2003 International Union of Crystallography. 874-23-7 and 40401-39-6 are also occured in this study. URL: http://journals.iucr.org/e/issues/2003/11/00/om6177/index.html. CODEN: ACSEBH. ISSN: 1600-5368. DOCUMENT TYPE: Journal; (online computer file) CA Section: 75 (Crystallography and Liquid Crystals) Section cross-reference(s): 28 Crystals of the title compd. are monoclinic, space group P21/c, with a 10.2097(6), b 7.5773(3), c 20.6921(12) ?, b 110.203(3)°; Z = 4, dc = 1.379; R = 0.051, Rw(F2) = 0.128 for 3431 reflections. The compd. shows no unusual features. There is no H-bonding or p-p stacking. .