Palladium-Catalyzed Ring-Forming Alkene Aminoaroylation of Unsaturated Hydrazones and Sulfonamides
摘要:
The first example of a Pd(OAc)(2)-catalyzed ring-forming alkene aminoaroylation of unsaturated hydrazones and sulfonamides is described. This protocol features the use of diaryliodonium salts as both oxidants and aryl sources, thus enabling mild reaction conditions, good chemoselectivity, a broad substrate scope, and high functional group tolerance. A wide range of synthetically and biologically important functionalized dihydropyrazoles and isoxazolidines have been obtained in good yields.
Stereoselective Palladium-Catalyzed Functionalization of Homoallylic Alcohols: A Convenient Synthesis of Di- and Trisubstituted Isoxazolidines and β-Amino-δ-Hydroxy Esters
作者:Andrei V. Malkov、Maciej Barłóg、Lucie Miller-Potucká、Mikhail A. Kabeshov、Louis J. Farrugia、Pavel Kočovský
DOI:10.1002/chem.201102716
日期:2012.5.29
Enantiopure, Boc‐protected alkoxyamines 12 and 13, derived from the readily available homoallylicalcohols 4 via a reaction that involves either inversion or retention of configuration, undergo a diastereoselective Pd‐catalyzed ring‐closing carbonylative amidation to produce isoxazolidines 16/17 (≤50:1 diastereoisomer ratio (d.r.)) that can be readily converted into the N‐Boc‐protected esters of β‐amino‐δ‐hydroxy
N-arylation-carbo-amination-C-arylation of O-homoallylhydroxylamines with two different aryl bromides provides rapid entry to differentially arylated N-aryl-3-arylmethylisoxazolidines in good yields with excellent diastereoselectivity. The obtained isoxazolidines can be reductively cleaved to cis-N-aryl-beta-amino alcohols in short times and in high yields at room temperature.
Palladium-Catalyzed Highly Stereoselective Synthesis of <i>N</i>-Aryl-3-arylmethylisoxazolidines via Tandem Arylation of <i>O</i>-Homoallylhydroxylamines
The palladium-catalyzed tandem arylation of O-homoallylhydroxylamines with 2 equiv of aryl bromides was examined. With Pd2(dba)3 (1 mol %) as the catalyst, Xantphos (2 mol %) as the ligand, and NaOt-Bu as the base, the reactions of O-homoallylhydroxylamines with aryl bromides via sequential N-arylation/cyclization/C-arylation in toluene afforded the corresponding N-aryl-3-arylmethylisoxazolidines in
Influence of Hydroxylamine Conformation on Stereocontrol in Pd-Catalyzed Isoxazolidine-Forming Reactions
作者:Georgia S. Lemen、Natalie C. Giampietro、Michael B. Hay、John P. Wolfe
DOI:10.1021/jo8027399
日期:2009.3.20
Palladium-catalyzed carboamination reactions between N-Boc-O-(but-3-enyl)hydroxylamine derivatives and aryl or alkenyl bromides afford cis-3,5- and trans-4,5-disubstituted isoxazolidines in good yield with up to >20:1 dr. The diastercoselectivity observed in the formation of cis-3,5-disubstituted isoxazolidines is superior to selectivities typically obtained in other transformations, such as 1,3-dipolar cycloaddition reactions, that provide these products. In addition, the stereocontrol in the C-N bond-forming Pd-catalyzed carboamination reactions of N-Boc-O-(but-3-enyl)hydroxylamines is significantly higher than that of related C-O bond-forming carboetherification reactions of N-benzyl-N-(but-3-enyl)hydroxylamine derivatives. This is likely due to a stereoelectronic preference for cyclization via transition states in which the Boc group is placed in a perpendicular orientation relative to the plane of the developing ring, which derives from the conformational equilibria of substituted hydroxylamines.
Palladium(0)-catalyzed cascade one-pot synthesis of isoxazolidines
作者:Krishna Gopal Dongol、Boon Ying Tay
DOI:10.1016/j.tetlet.2005.11.148
日期:2006.2
A highly diastereoselective cascade reaction protocol has been developed for the synthesis of isoxazolidine derivatives utilizing aryl halides, O-homoallyl hydroxylamine and palladium(0) in a one-pot reaction. (c) 2005 Elsevier Ltd. All rights reserved.