73130-08-2Relevant articles and documents
Palladium-Catalyzed Pyrazole-Directed sp3 C?H Bond Arylation for the Synthesis of β-Phenethylamines
Gulia, Nurbey,Daugulis, Olafs
, p. 3630 - 3634 (2017)
We have developed a method for palladium-catalyzed, pyrazole-directed sp3 C?H bond arylation by aryl iodides. The reaction employs a Pd(OAc)2 catalyst at 5–10 mol % loading and silver(I) oxide as a halide-removal agent, and it proceeds in acetic acid or acetic acid/hexafluoroisopropanol solvent. Ozonolysis of the pyrazole moiety affords pharmaceutically important β-phenethylamines.
A new germanium-based linker for solid phase synthesis of aromatics: Synthesis of a pyrazole library
Spivey, Alan C.,Diaper, Christopher M.,Adams, Harry,Rudge, Andrew J.
, p. 5253 - 5263 (2007/10/03)
An efficient synthesis of chlorogermane linker 12 is described. Economic introduction of germanium into this linker is accomplished by insertion of dichlorogermylene [from germanium(IV) chloride] into the homobenzylic C-Cl bond of 4-(2-chloroethyl)phenol 1. Using linker 12, transmetalation with lithiated 4-acetophenone, 3-acetophenone, and 4-(4'methoxy)biphenyl followed by Mitsunobu-type coupling to Argogel gives functionalized resins 14, 16, and 18, respectively. Treatment of resin 18 with TFA, ICl, Br2, or NCS effects clean ipso-degermylation releasing biphenyls 19-22, respectively. Resins 14 and 16 are employed for the parallel synthesis of a library of pyrazoles by enaminone formation (using Bredereck's reagent), condensative ring-closure (using a series of monosubstituted hydrazines), and cleavage (using TFA and Br2). Analysis of this library reveals the influence of the hydrazine substituent on both the regioselectivity of ring-closure and the propensity for electrophilic substitution at the 4-position of the pyrazoles during ipso-degermylative cleavage.
