Low-valent titanium and zirconium reagents in situ prepared from metallocene dichlorides (Cp2MCl2: M = Ti, Zr) and magnesium powder activated by 1,2-dibromoethane smoothly reacted with allylpropargylethers to afford 3-methylenetetrahydrofurans in good yields. It is noteworthy that the Cp2Zr- and Cp2Ti-mediated cyclizations proceed with inverse stereoselectivity.
Ligand-Switchable Directing Effects of Tethered Alkenes in Nickel-Catalyzed Additions to Alkynes
作者:Karen M. Miller、Timothy F. Jamison
DOI:10.1021/ja0446799
日期:2004.12.1
Nickel-catalyzed reductive couplings of aldehydes with alkynes that contain tethered olefins are described, in which the degree and sense of regioselectivity are controlled by the length of the tether and the presence or absence of an additive. When the alkyne and alkene are separated by four bonds, very high (>95:5) regioselectivities are observed. Use of a monodentate phosphine as an additive leads
Tandem Insertion of Halocarbenoids and Lithium Acetylides into Zirconacycles: A Novel Rearrangement to Zirconium Alkenylidenates by β-Addition to an Alkynyl Zirconocene
作者:Jozef Stec、Emma Thomas、Sally Dixon、Richard J. Whitby
DOI:10.1002/chem.201002962
日期:2011.4.18
Tandem insertion of 1,1‐dihalo‐1‐lithio species (halocarbenoids) and lithium alkynides into zirconacyclopentenes and zirconcyclopentanes affords carbocyclic products in high yields via an unusual rearrangement that probably involves addition of an organolithium species to the β‐position of a zirconium–alkyne complex to give an alkenylidene–zirconate species. A wide variety of cyclopentanoid organic
Aldehyde Addition and Copper-Mediated Allylation of Bicyclic Alkoxytitanacyclopentenes and -Pentadienes: New Selectivities and an Unusual Reaction
作者:Hirokazu Urabe、Fumie Sato
DOI:10.1021/ja982501e
日期:1999.2.1
Bicyclic titanacyclopentenes generated in situ from 1,6-enynes and (eta(2)-propene)Ti(O-i-Pr)(2) (1) reacted with aldehydes at their alkenyl-titanium bond in the absence or presence of Ti(O-i-Pr)(n)Cl(4-n) (n = 2 or 3) to give allyl alcohols such as 5-7 as a nearly single stereoisomer in good yields. Upon workup with DCl/D(2)O or iodine, deuterio and iodo derivatives, 8 and 9, were obtained. Bicyclic titanacyclopentadienes prepared analogously from 1,6- or 1,7-diynes and 1 also reacted with aldehydes in the presence of an additional equivalent of Ti(O-i-Pr)(2)Cl(2) to afford 1,2-dialkylidenecyclopentanes pr -cyclohexanes having an alcohol moiety in their side chain in good yields. In place of the simple hydrolysis, deuteriolysis or iodinolysis gave the corresponding derivatives such as 21 or 22. Treatment of 1,6-enyne 10 with 1 in the standard way and then with a slight excess of i-PrMgCl at -50 degrees C generated a new titanium species that, upon reaction with aldehydes, afforded unexpected adducts 34 and 41-45 virtually as a single isomer. Copper-mediated allylation of dialkoxytitanacyclopentene such as 3 with allyl bromide proceeded at their vinyl-titanium bond to give 48 and 50. Likewise, dialkoxytitanacyclopentadiene prepared from 29 and 1 underwent the regioselective copper-mediated mono-allylation to give a 9:1 mixture of 53 and 54. Upon workup with deuteriochloric acid, the corresponding deuterated product was obtained with a high degree of deuterium incorporation.
Small Molecule Agonists of the Orphan Nuclear Receptors Steroidogenic Factor-1 (SF-1, NR5A1) and Liver Receptor Homologue-1 (LRH-1, NR5A2)
作者:Richard J. Whitby、Jozef Stec、Raymond D. Blind、Sally Dixon、Lisa M. Leesnitzer、Lisa A. Orband-Miller、Shawn P. Williams、Timothy M. Willson、Robert Xu、William J. Zuercher、Fang Cai、Holly A. Ingraham
DOI:10.1021/jm1014296
日期:2011.4.14
The crystal structure of LRH-1 ligand binding domain bound to our previously reported agonist 3-(E-oct-4-en-4-y1)-1-phenylamino-2-phenyl-cis-bicyclo[3.3.0]oct-2-ene 5 is described. Two new classes of agonists in which the bridgehead anilino group from our first series was replaced with an alkoxy or 1-ethenyl group were designed, synthesized, and tested for activity in a peptide recruitment assay. Both new classes gave very active compounds, particularly against SF-1. Structure-activity studies led to excellent dual-LRH-1/SF-1 agonists (e.g., RJW100) as well as compounds selective for LRH-1 (RJW101) and SF-1 (RJW102 and RJW103). The series based on 1-ethenyl substitution was acid stable, overcoming a significant drawback of our original bridgehead anilino-substituted series. Initial studies on the regulation of gene expression in human cell lines showed excellent, reproducible activity at endogenous target genes.